Protocols & Procedures (WIP)

General Overview A lighting plant consists of the electrical distribution system and one or more light fixture systems. The electrical distribution system provides power to the light fixture system, which provides the actual illumination to indoor spaces, emergency evacuation routes, and outdoor areas. The electrical distribution system receives electricity from the power grid, which then is distributed through switchgear and panelboards. A lighting plant and associated systems are shown in Figure 1. Measurements may be taken at the electrical distribution or light fixture system levels. Figure 1. Lighting Plant. Keep in mind that a lighting plant will have several electrical panelboards (click on image to enlarge). Systems Electrical Distribution System The electrical distribution system is comprised of main and secondary switchgear and panelboards. The switchgear distributes electricity to the panelboards, and the panelboards provide electricity to the light fixture systems. Panelboards typically serve light fixture systems in multiple spaces across a facility and are generally broken down by floor or smaller spaces on a floor. Sometimes multiple electric panelboards are required to provide power to a single space such as a warehouse, gymnasium, or garage. Learn More Figure 2. Electrical distribution system (click on image to enlarge). note Panelboards can have mixed loads or be dedicated just to lighting. Mixed panelboards serve the light fixture systems and other electrical loads such as receptacles, office equipment or miscellaneous plug loads. Dedicated panelboards exclusively serve light fixture systems including interior, exterior, and emergency lighting. Light Fixture System The light fixture system is comprised of the luminaires, lamps, and controls. Controls can be manual or automatic. All lighting systems have some form of manual controls such as wall switches within a space or electrical disconnects (circuit breakers) at the panelboard. Some lighting systems have automatic controls which may include a control panel and sensors. Learn More Figure 3: Two Dedicated Lighting Panelboards with Automatic Controls, each panelboard is considered a system (click on image to enlarge). Evaluation of Energy Consumption To quantify the energy consumption of the lighting plant, the components of all lighting systems should be measured. Some facilities may have a combination of the above-mentioned systems and a level of engineering judgement will be necessary to determine how much of what to measure. Table 1. Key values and components to measure to evaluate energy consumption. Plant Quantification Values to be Quantified Energy Consuming Component Lighting plant electricity usage (kWh) Average hourly kWh served by the electrical distribution system Light fixtures and automatic controls (if applicable). Further Reading Richman, EE. (2016). “Measurement and Verification of Energy Savings and Performance from Advanced Lighting Control.” Richland, WA: Pacific Northwest National Laboratory.

General Overview A lighting fixture system produces light to illuminate a specific area or areas. Current is received from the electrical distribution system. The group of fixtures that comprise a lighting system can be configured in many ways with different lamp types and a building can have one or more lighting fixture systems. The main components of an individual lighting fixture are lamps, ballasts, and controls. Components Figure 1 shows the main components associated with a lighting fixture system. Figure 1. Lighting Fixture System, fixtures are of a single type in this room (click on image to enlarge). Figure 2: Lighting fixture system of the building consists of many different types of fixtures (i.e., fixtures that consume different amounts of energy) (click on image to enlarge). Lamps Lamps refer to the enclosure of the lighting source. The most common types of lamps are incandescent, fluorescent, high intensity discharge (HID), induction and LED. Many types of lamps can be used within a facility. All lamps convert electrical energy to light, with some energy converted to heat as well. The efficiency of the lamp in minimizing losses to heat is the biggest determining factor in the energy efficiency of the lighting fixture system. In addition to electrical efficiency, different lamps produce different color spectrums, which are better suited to different applications. For example, an office typically requires white light with a “cool” tone. However, warehouse lighting may be more yellow or orange without impacting its function. Ballast The ballast is an electrical device that regulates the voltage and current supplied to a lamp. Incandescent lamps do not require ballasts; however, all other lamp types require well-regulated voltage and current to operate and therefore need ballasts. There are many types of ballasts, and they are compatible with specific lamps. Some fixture systems have the ballast integrated into the lamp component. The regulation of voltage and current causes some energy loss to heat and ballasts have different energy efficiencies based on how well they minimize these losses. Housing The fixture housing is the physical receptacle that houses the lamp and ballast. The housing may include shutters or diffusers which direct and disperse the light. Some housing is designed to disperse the heat generated by the lamp and ballast more effectively, which increases the life of the fixture. Controls Controls regulate the operation of the light fixtures, such as when they are turned on and off and their brightness. Controls can be manual or automatic. Manual controls are wall switches within a space and circuit breakers at the electrical panelboard and switchgear. Automatic controls use sensors and/or timers to determine when and how to regulate the fixture operation. The two most common sensors used in lighting controls are motion sensors, which approximate when a space is occupied or not and daylight sensors which determine when natural sources are providing enough light for the fixtures to be turned off or dimmed. Some automatic controls have their own control panel that is wired directly to the circuits at the lighting panelboards or the ballasts of individual fixtures. Evaluation of Energy Consumption Electricity is the energy source for all modern lighting systems. Table 1 provides a summary of system component measurements and values needed to quantify the hourly energy consumption and operating characteristics of a lighting fixture system. Table 1. Key values, components and measurements to evaluate energy consumption. System Quantification Values to be Quantified Energy Consuming Component Measurements Lighting fixture system electricity usage (kWh) Average hourly panelboard or switchgear (kWh) Total operating time for the light fixtures Light fixtures and automatic controls (if applicable). Hourly measurement of electricity supplied to the light fixture system from the panelboard or switchgear Total operating hours of the light fixtures Illuminance delivered Lumens Light fixtures Lumens incident on surfaces that require illumination (workstations, walkways, shelving, etc.) Light quality Color rendering index Lamps Color rendering index measurement (speciality equipment) Measurement Locations Electrical measurements of lighting fixtures must be taken at the electrical distribution components. Further details can be found in the Electrical Distribution page. An auditor can develop a sampling plan and use a light on/off logger to measure the schedule of a single fixture. The single light fixture should be representative of the other fixtures in the room to assume the same schedule for all fixtures. Then a direct power draw measurement at the electrical panelboard that serves the fixture is needed. The power draw data and the schedule data obtained from the light on/off logger allows an auditor to estimate energy consumption. Figure 3. Lighting fixture measurement locations (click on image to enlarge). Figure 4: Electrical measurement necessary to estimate energy. Measurement is taken at the electrical panelboard that serves the lighting fixtures (click on image to enlarge). Calculation Methodology Lighting Plant and Systems Energy Consumption Calculation The equations and calculators in this page estimate the annual energy consumption of the lighting plant. Further Reading California Energy Commission (June 2015). 2016 Building Energy Efficiency Standard for Residential and Nonresidential Buildings, Title 24, Part 6, Chapter 6: Residential Compliance Manual, CA: California.

General Overview An electrical distribution system is made up of switchgear and panelboards connected by wires. Switchgear is used to disaggregate the power coming from the utility grid to serve various aggregate loads in a facility, such as lights, motors, receptacle circuits, or miscellaneous equipment. A panelboard is used as the final disconnect and protection point for individual circuits in a space. A lighting panelboard is connected to the light fixture system in one or more spaces, typically on a single floor of a facility, or the outdoor light fixture system. Panelboards may be dedicated to the lighting system or “mixed” serving both lighting loads and other circuits. Components Figure 1 shows the main components associated with the electrical distribution system: switchgear and panelboard. Figure 1. Diagram of an electrial distribution system (click on image to enlarge). Switchgear Switchgear is an assembly that contains circuit breakers, fuses and other accessories to interrupt current flow and protect electrical equipment and occupants. The electricity delivered by a utility company is passed through a step-down transformer and then to a switchgear as the first layer of protection in a facility. Then electricity is distributed among other assemblies such as a secondary switchgear or panelboards. The configuration of primary and secondary switchgears is dependent on the facility. Not all facilities will have secondary switchgear. Dedicated Panelboard A dedicated electrical panelboard supplies electricity only to the light fixture system. Figure 2 shows a dedicated panelboard without a panel cover to show how the electrical wiring is distributed. The electricity from the primary or secondary switchgear enters from the top (or bottom) of the panelboard then splits across all the branch circuits. Figure 2. Dedicated panelboard system (click on image to enlarge). Figure 3 is an example of a schedule of circuits on a dedicated panelboard. The schedule typically describes the type of load (e.g., lights) and the space that is served by the breaker. There is no standard naming convention for circuits. Figure 3. Example of a dedicated panelboard schedule (click on image to enlarge). Mixed Panelboard A Mixed electrical panelboard supplies electricity to the lighting fixture system and other loads, typically receptacle circuits. Mixed panelboards typically exist in small or older facilities. The electricity from the primary or secondary switchgear enters from the top (or bottom) of the panelboard then splits across all of the branch circuits. The interior of a mixed panelboard will look similar to Figure 2 but the panel schedule will highlight a collection of different loads as shown in Figure 4. Figure 4: Example of a mixed panelboard schedule (click on image to enlarge).1 Evaluation of Energy Consumption The electrical distribution system does not consume electricity, but it can be a useful point at which to measure the electrical energy associated with the Lighting Plant. Table 1. Key values, components and measurements to evaluate energy consumption. System Quantification Values to be Quantified Energy Consuming Component Measurements Lighting fixture system electricity consumption (kWh) Average hourly panelboard or switchgear kWh Total operating time for the light fixtures Light fixtures and automatic controls (if applicable). Average hourly electricity supplied to the light fixture system from the switchgear or panelboard Total operating hours of the light fixtures Measurement Locations Figures 5 and 6 show typical measurement locations in an electrical distribution system. Figure 5: Three-phase power measurement using a Dent EliteProXC Power Logger to capture to total power draw of all fixtures served by the panelboard (click on image to enlarge). Figure 6: Current measurement using current transformers and a data logger to collect measurement data. In this figure measurements are taken at the circuit breaker level to capture specific fixtures. Voltage and power factor measurements are taken with a power meter (click on image to enlarge). Measurement locations in the electrical distribution system are at the conductors in the panelboard or switchgear. To measure a lighting plant, the best practice is to capture as much of the lighting plant in a single measurement as possible. Measuring at switchgear may be appropriate if all lighting panelboards are dedicated and connected to it, but only the distribution line that supplies electricity to lighting should be measured. Alternatively, a sample of panelboards and/or circuits can be measured but a sampling plan must be considered. For more information on sampling please refer to Bonneville Power Administration’s guide on sampling. Calculation Methodology Lighting Plant and Systems Energy Consumption Calculation The equations and calculators in this page estimate the annual energy consumption of the lighting plant. Further Reading Consulting-Specifying Engineer (20). “Back to Basics: Switchgear, Transformers and UPSs.”. https://www.csemag.com/articles/back-to-basics-switchgear-transformers-and-upss/; accessed May 24, 2022. Bonneville Power Administration (July 2018). “Sampling for M&V: Reference Guide.” EE Richman (February 2016). PNNL-SA-25222. “Measurement and Verification of Energy Savings and Performance from Advantage Lighting Controls” Richland, WA: Pacific Northwest National Laboratory. Footnotes Blue represents lighting fixtures, red represents others electrical loads. ↩︎

Introduction The calculation tools developed by CUNY BPL are used to calculate annual energy consumption and not for estimating savings. All calculation tools start by using input data (lighting runtime, AC current, etc.) to calculate hourly energy (kWh). Then data is averaged by hour of day and day of the week to get an approximation of how light fixtures operate during any hour of the week. Weekends and weekdays are extrapolated and summed to obtain a full-year estimate. To calculate savings, use the calculation tools with pre- and post-retrofit data and compare the energy consumption results. The calculation tools will extrapolate data to a full year regardless of how much input data is used, but a minimum of six (6) weeks of data at one-hour intervals is required to adhere to Measurement and Verification standards. If the total fixture inventory for the project is known, data can be used by the calculation tools to determine how much of the lighting load was directly measured, but this data is not necessary for the calculation tools to work. This is useful for someone who only measured a sample of fixtures as part of a sampling plan and wants to compare the annual estimates to the total lighting load. All lighting calculation tools generate an average hourly energy schedule using the input data. The schedule can be used to determine the interactive heating and cooling effects associated with the lighting retrofit but this requires separate analysis. The first three methodologies are used when measuring electricity with data loggers and power meters to determine the annual energy consumption estimate of an electrical distribution system. The last methodology is used when measuring lighting runtime (operating schedule) to determine the annual energy consumption estimate of a lighting fixture system. Calculators Table 1. Lighting energy calculators Calculator (Downloadable Files) Description Required Data To Use This Calculator Lighting True RMS Power Output from Electric Panelboard.xlsx Uses the runtime and power of the panelboard to calculate the annual anergy consumption of a lighting electrical distribution system. Hourly lighting runtime Expected fixture wattage Fixture counts True RMS Power (total power draw) (kW) Lighting Electrical Current Output from Electric Panelboard.xlsx Uses voltage measurements alongside power, circuit amperage and current from the electrical panelboard to measure the total energy output from the system. Circuit voltage (V) Power factor (kW) Hourly current (amps) Lighting Electrical Current from Circuit Breakers.xlsx Uses voltage measurements alongside power, circuit amperage and current from circuit breakers to measure the total energy output from the system. Circuit voltage (V) Power factor (kW) Hourly current (amps) Lighting Inventory and Operating Schedule.xlsx Uses the panel energy use to calculate the operating schedule of the system. Lighting Panel Total Energy Use (kW) Lighting Energy Consumption Lighting True RMS Power Output from Electric Panelboard The following equations are used to calculate the annual energy consumption of a lighting electrical distribution system where energy in kilowatt hours (kWh) is measured at the output end of an electrical panelboard or switchgear. It is assumed that data is collected for six (6) weeks at one-hour intervals with a data-logging power meter that has the capacity to measure three-phase power. Find hourly average energy use for each hour of each day of the week (Worksheet: “Step 2. Avg Energy Calcs,” column J.) $$\begin{array}{}\text{(27)}& {\overline{kWh}}_{d,h}=\frac{\sum _1^{N_f(d,h)}kW{h}_n}{N_f(d,h)}\end{array}$$ Where, ${\overline{kWh}}_{d,h}=$ Average energy of each hour for each day of the week (in kWh) $kW{h}_n=$ Measured hourly energy kWh from the data-logging power logger (in kWh) $N_f(d,h)=$ Total number of measuremed data points that fall on day of week, d, and hour the day, h Find total daily energy consumption (Worksheet: “Step 3. Results,” column C, “Step 3. Hourly Results.") $$\begin{array}{}\text{(28)}& {\overline{kWh}}_d=\sum _{h=0}^{23}{\overline{kWh}}_{d,h,n}\end{array}$$ Where, ${\overline{kWh}}_d=$ Sum of energy consumption for each day of the week (in kWh) ${\overline{kWh}}_{d,h}=$ Average energy of each h hour for each day of the week (in kWh) $h=$ Hour of the day where 0 is 12:00 a.m. and 23 is 11:00 p.m. Calculate the average energy consumption for weekdays (Worksheet: “Step 3. Results,” cell D3.) $$\begin{array}{}\text{(29)}& {\overline{kWh}}_{Wd}=\frac{\sum _{d=2}^6{\overline{kWh}}_{w,d}}{5}\end{array}$$ Where, ${\overline{kWh}}_{Wd}=$ Average energy consumption for weekdays (in kWH) ${\overline{kWh}}_{w,d}=$ Average energy of each n weekday (in kWh) $d=$ day of week: (2 = Monday, 3 = Tuesday, ... 6 = Friday) Calculate the average energy consumption for weekend days (Worksheet: “Step 3. Results,” cell D6.) $$\begin{array}{}\text{(30)}& {\overline{kWh}}_{WEd}=\frac{{\overline{kWh}}_{we,1}+{\overline{kWh}}_{we,7}}{2}\end{array}$$ Where, ${\overline{kWh}}_{WEd}=$ Average energy consumption for each day of the week (in kWh) ${\overline{kWh}}_{we,d}=$ Average energy of each n weekend day (in kWh) $d=$ Day of week: (7 = Saturday, 1 = Sunday) Calculate the annual weekday energy consumption (Worksheet: “Step 3. Results,” cell E3.) $$\begin{array}{}\text{(31)}& {\overline{kWh}}_{WdYr}={\overline{kWh}}_{Wd}\ast (261weekdaysperyear-X)\end{array}$$ Where, ${\overline{kWh}}_{WdYr}=$ Annual weekday energy consumption (in kWh) ${\overline{kWh}}_{Wd}=$ Average weekday energy consumption (in kWh) $X=$ Number of weekdays that are adjusted to use weekend day average energy consumption Calculate the total weekend day energy consumption (Worksheet: “Step 3. Results,” cell E6.) $$\begin{array}{}\text{(32)}& {\overline{kWh}}_{WEdYr}={\overline{kWh}}_{WEd}\ast (104weekenddaysperyear+X)\end{array}$$ Where, ${\overline{kWh}}_{WEdYr}=$ Annual weekend day energy consumption (in kWh) ${\overline{kWh}}_{Wd}=$ Average weekday day energy consumption (in kWh) $X=$ Number of weekdays that are adjusted to use weekend day average energy consumption Calculate total annual estimate energy consumption (Worksheet: “Step 3. Results,” cell F3.) $$\begin{array}{}\text{(33)}& {\overline{kWh}}_{anm}={\overline{kWh}}_{WdYr}+{\overline{kWh}}_{WEdYr}\end{array}$$ Where, ${\overline{kWh}}_{ann}=$ Annual energy consumption (in kWh) ${\overline{kWh}}_{WdYr}=$ Annual weekday energy consumption (in kWh) ${\overline{kWh}}_{WEdYr}=$ Annual weekend day energy consumption (in kWh) If more than one electric panel or switchgear was measured, sum the annual energy consumption of all panels to find the total energy consumption of the electrical distribution system. $$\begin{array}{}\text{(34)}& \overline{kWh}={\overline{kWh}}_{n_1}+{\overline{kWh}}_{n_2}+...\end{array}$$ Where, $\overline{kWh}=$ Total energy consumption for the electrical distribution system (in kWh) ${\overline{kWh}}_n=$ Total energy consumption for each panel or switchgear(in kWh) $n=$ Number of panels or switchgear measured Lighting Electrical Current Output from Electric Panelboard Lighting fixtures generally require single-phase power to operate but electrical distribution systems are commonly three-phase. This methodology only applies to a three-phase, four wire system (wye configuration), additionally the panelboard load must be balanced (i.e., all three electrical lines, or phases, must have the same current and line-to-neutral voltage.) For an unbalanced load, where voltage and current are not equal across the three lines, energy should be measured directly with a data-logging power logger capable of measuring a three-phase system, see section A.1. To estimate the energy consumption of the panelboard, including all fixtures served by it, current should be measured for all three electrical lines of the three-phase system. Current data should be at one-hour intervals and data should consist of an average sample of measurements1 for each one-hour interval. Power factor, line-to-line voltage, and true RMS power can be obtained from spot measurements with a handheld power meter. CUNY BPL recommends taking multiple spot measurements of those variables and averaging them (e.g., measure power factor at least three times at five-minute intervals and calculate the average), see equation (9). The average of the spot measurements helps reduce measurement uncertainty and should be used as inputs to the calculation tools. Equation (9) should be applied to power factor, voltage, and true RMS power. $$\begin{array}{}\text{(35)}& \overline{PF}=\frac{P{F}_{t1}+P{F}_{t2}+P{F}_{t3}+P{F}_{tx}}{x}\end{array}$$ Where, $\overline{PF}=$ Average of measured power factor $PF=$ Spot measurement of power factor at the panelboard $t1=$ First measurement $t2=$ Second measurement, at least five minutes after the first measurement $t3=$ Third measurement, at least five minutes after the second measurement $x=$ Number of spot measurements taken, at least five minutes apart $$\begin{array}{}\text{(36)}& V_{avg,LL}=\frac{V_{t1}+V_{t2}+V_{t3}+V_{tx}}{x}\end{array}$$ Where, $V_{avg,LL}=$ Average line-to-line voltage $V_{t1}=$ First measurement of voltage $V_{t2}=$ Second measurement of voltage, at least five minutes after the first measurement $V_{t3}=$ Third measurement of voltage, at least five minutes after the second measurement $x=$ Number of spot measurements taken, at least five minutes apart Find the average current of the electrical distribution system for each hour interval. Current of all three phases is measured every hour, in this step the average current of the panelboard is calculated for each hour interval. $$\begin{array}{}\text{(37)}& I_{h,avg}=\frac{I_1+I_2+I_3}{3}\end{array}$$ Where, $I_{h,avg}=$ Average current for each hour interval (in Amps) $I_1=$ Hourly average current of line 1 (in Amps) $I_2=$ Hourly average current of line 1 (in Amps) $I_3=$ Hourly average current of line 3 (in Amps) Equation 11 calculates the three-phase power of the panelboard if line-to-line voltage is measured. If line-to-neutral voltage is measured (from hot wire to ground) the square root of 3 should be replaced with 3 and the line-to-neutral voltage should be used. Calculate three-phase power for each hour interval using the results from equation (8), (9) and (10) (i.e., average current for each hour interval, average voltage, and average power factor). (Worksheet: “Step 2. Power Calcs,” column E, G, I.) $$\begin{array}{}\text{(38)}& {\overline{kW}}_{h,3P}=\frac{\sqrt{3}\ast I_{h,avg}\ast V_{LL,avg}\ast PF}{1000}\end{array}$$ Where, ${\overline{kW}}_{h,3P}=$ Hourly three-phase power draw of the panelboard (in kW) $I_{h,avg}=$ Average current for each hour interval (in Amps) $V_{LL,avg}=$ Measured average line-to-line voltage (in V) $PF=$ Measured average power factor $$\begin{array}{}\text{(39)}& {\overline{kW}}_{h,3P}=\sum _{n=1}^3{\overline{kW}}_{h,n}\end{array}$$ Where, ${\overline{kW}}_{h,3P}=$ Hourly three-phase power draw of the panelboard (in kW) ${\overline{kW}}_{h,n}=$ Hourly single-phase power for electrical line n (in kW) -- Calculate average energy consumption for each hour of each day of the week (Worksheet: “Step 3. Avg Energy Calcs,” column C.) This equation helps to reduce the amount of data points to a week by taking the average of each hour for a given day of the week. In this step the hourly power draw (kW) gets converted to hourly energy consumption (kWh) because data is in one-hour intervals. kWh = kW ∗ h, where h = 1. $$\begin{array}{}\text{(40)}& {\overline{kWh}}_{d,h}=\frac{\sum _1^{N_f(d,h)}k{W}_{h,3P}}{N_f(d,h)}\end{array}$$ Where, ${\overline{kWh}}_{d,h}=$ Average energy consumption for each hour of each day of the week (in kW) ${\overline{kW}}_{h,3P}=$ Hourly three-phase power draw of the panelboard (in kW) $N_f(d,h)=$ Total number of data points that fall on day of week, d, and hour of the day, h Calculate total hourly energy consumption for a given day of the week (Worksheet: “Step 4. Results,” column C.) $$\begin{array}{}\text{(41)}& {\overline{kWh}}_{d,w}=\frac{\sum _{h=0}^{23}{\overline{kWh}}_{d,h}}{h}\end{array}$$ Where, ${\overline{kWh}}_{d,w}=$ Average hourly energy consumption for a given day of the week of the three-phase panelboard (in kWh) ${\overline{kWh}}_{d,h}=$ Average energy consumption for each hour of each day of the week (in kWh) $h=$ Hour of the day where 0 is 12:00 a.m. and 23 is 11:00 p.m. Calculate the average energy consumption for weekdays (Worksheet: “Step 4. Results,” cell D3.) $$\begin{array}{}\text{(42)}& {\overline{kWh}}_{Wd}=\frac{\sum _{d=2}^6{\overline{kWh}}_{w,d}}{5}\end{array}$$ Where, ${\overline{kWh}}_{Wd}=$ Average energy consumption for weekdays (in kWh) ${\overline{kWh}}_{wd,n}=$ Average hourly energy consumption of each n weekday (in kWh) $d=$ Day of week (2 = Monday, 3 = Tuesday, ..., 6 = Friday) $24=$ Constant, hours per day $5=$ Constant, weekdays per week Calculate the average energy consumption for weekend days (Worksheet: “Step 4. Results,” cell D6.) $$\begin{array}{}\text{(43)}& {\overline{kWh}}_{WEd}=\frac{{\overline{kWh}}_{we,1}+{\overline{kWh}}_{we,7}}{2}\end{array}$$ Where, ${\overline{kWh}}_{WEd}=$ Average energy consumption for a weekend day (in kWh) ${\overline{kWh}}_{we,n}=$ Average energy consumption of each n weekend day (in kWh) $n=$ Day of week (7 = Saturday, 1 = Sunday) $2=$ Constant, weekends per week Calculate the total annual weekday energy consumption (Worksheet: “Step 4. Results,” cell E3.) $$\begin{array}{}\text{(44)}& {\overline{kWh}}_{WdYr}={\overline{kWh}}_{Wd}\ast (261-X)\end{array}$$ Where, ${\overline{kWh}}_{WdYr}=$ Estimated annual weekday energy consumption (in kWh) ${\overline{kWh}}_{Wd}=$ Average energy consumption for weekdays (in kWh) $X=$ Number of weekdays that are considered holidays and adjusted to weekend day average energy consumption $261=$ Constant, number of weekdays per year Calculate the total annual weekend day energy consumption (Worksheet: “Step 4. Results,” cell E6.) $$\begin{array}{}\text{(45)}& {\overline{kWh}}_{WEdYr}=\overline{kWh}\ast (104+X)\end{array}$$ Where, ${\overline{kWh}}_{WEdYr}=$ Annual weekend day energy consumption (in kWh) ${\overline{kWh}}_{WEd}=$ Average weekend day energy consumption (in kWh) $X=$ Number of weekdays that are considered holidays and adjusted to weekend day average energy consumption $104=$ Constant, number of weekend days per year Calculate total annual energy consumption of the panelboard $$\begin{array}{}\text{(46)}& {\overline{kWh}}_{ann}={\overline{kWh}}_{WdYr}+{\overline{kWh}}_{WEdYr}\end{array}$$ Where, ${\overline{kWh}}_{ann}=$ Estimated annual energy consumption of the panelboard (in kWh) ${\overline{kWh}}_{WdYr}=$ Estimated annual weekday energy consumption (in kWh) ${\overline{kWh}}_{WEdYr}=$ Estimated annual weekend day energy consumption (in kWh) If more than one panelboard was measured sum the annual energy consumption of all panels to find the total energy consumption of all measured panelboards. $$\begin{array}{}\text{(47)}& \overline{kWh}={\overline{kWh}}_{n_1}+{\overline{kWh}}_{n_1}+...\end{array}$$ Where, $\overline{kWh}=$ Total energy consumption of all measured panelboards (in kWh) ${\overline{kWh}}_n=$ Total energy consumption for each panelboard (in kWh) $n=$ Number of panelboards measured Lighting Electrical Current from Circuit Breakers Lighting fixtures generally require single-phase power to operate but electrical distribution systems are commonly three-phase. When measuring individual circuits of a panelboard it is important to know what phase the circuit is connected to. This is because the proper line-to-neutral connection is required to accurately measure voltage for that circuit. The calculation tool requires the phase of the circuit to be specified to calculate annual energy consumption. If multiple circuits are measured and are connected to the same phase, then only the voltage of that phase is necessary Additionally, the user should note if the panelboard is balanced (i.e., all three electrical lines, or phases, must have the same current and line-to-line voltage.) If the panelboard is not balanced, then it must be specified in the calculation tool (see worksheet ‘Step 1.1 Circuit Raw Data’) The following equations are used to calculate the annual energy consumption of a lighting electrical distribution system where AC current is measured at the output of circuit breakers in an electrical panelboard. AC current should be measured using a data logger with current transformers (e.g., Onset HOBO 4-channel analog logger and the Onset CTV-x current transformer sensors) for one or more circuit breakers; a group of circuits can be measured with a single transformer. Current data should be at one-hour intervals and data should be averaged with a sample of measurements1 for each one-hour interval. Voltage is obtained from spot measurements (i.e., measured one time) with a power meter at the circuit breakers. It is assumed that multiple spot measurements are taken and averaged (e.g., measure line-to-neutral voltage for a circuit breaker three times at five-minute intervals and calculate the average) see equation (20). The average value should be used with these equations to reduce measurement uncertainty. In this scenario, the line-to-neutral voltage is measured for a single circuit. If measuring multiple circuits be sure to take multiple spot measurements of line-to-neutral voltage for all circuits. $$\begin{array}{}\text{(48)}& V_{LN,avg}=\frac{V_{t1,n}+V_{t2,n}+V_{t3,n}+V_{tx,n}}{x}\end{array}$$ Where, $n=$ The electrical line that was measured of the three-phase system $V_{avg,n}=$ Average line-to-neutral voltage of a circuit in electrical line n $V_{t1,n}=$ First measurement of voltage for electrical line n $V_{t2,n}=$ Second measurement of voltage for electrical line n, at least five minutes after the first measurement $V_{t2,n}=$ Third measurement of voltage for electrial line n, at least five minutes after the second measurement $x=$ Number of spot measurements taken, at least five minutes apart For each circuit or group of circuits measured, calculate average power for each hour interval (Worksheet: “Step 2. Power Calcs.”) Power is calculated using line-to-neutral voltage and current of the circuit. $$\begin{array}{}\text{(49)}& {\overline{kW}}_{h,n}=\frac{I_n\ast V_{LN,avg}}{1000}\end{array}$$ Where, ${\overline{kW}}_{h,n}=$ Average hourly power for a circuit n (in kW) $I_n=$ Measured average houry current for a circuit (in Amps) $V_{I,N,avg}=$ Measured average line-to-neutral voltage for a circuit (in V) Calculate average energy use for each hour of each day of the week (Worksheet: “Step 3. Avg Energy Calcs, column C, D, E, F.”) In this step the hourly power draw (kW) gets converted to hourly energy consumption (kWh) because data is in one-hour intervals. kWh = kw * h, where h = 1. $$\begin{array}{}\text{(50)}& {\overline{kWh}}_{d,h,c}=\frac{\sum _1^{N_f(d,h)}k{W}_h}{N_f(d,h)}\end{array}$$ Where, ${\overline{kWh}}_{d,h,c}=$ Average energy of each hour for each day of the week for each circuit (in kWh) $k{W}_h=$ Total power at each hour of each day of each week (in kW) $N_f=$ Total number of measured data points that fall on day of week, d, and hour of the day, h Calculate the sum of average hourly energy of all circuits (Worksheet: “Step 3. Avg Energy Calc” column G.) $$\begin{array}{}\text{(51)}& {\overline{kWh}}_{d,h,n}=\sum _{c=1}^4{\overline{kWh}}_{d,h,c}\end{array}$$ Where, ${\overline{kWh}}_{d,h}=$ Total average energy for all circuits of each hour for each day of the week (in kWh) ${\overline{kWh}}_{d,h,c}=$ Total average energy for each hour for each day of the week for each circuit (in kWh) $c=$ Circuit that was measured Calculate total daily energy consumption for a given day of the wekk (Worksheet: “Step 4. Results,” column C.) $$\begin{array}{}\text{(52)}& {\overline{kWh}}_{d,w}=\sum _{n=0}^{23}{\overline{kWh}}_{d,h}\end{array}$$ Where, ${\overline{kWh}}_{d,w}=$ Total average energy for each day of the week (in kWh) ${\overline{kWh}}_{d,h}=$ Total average energy of each h hour for each day of the week (in kWh) $h=$ Hour of the day where 0 is 12:00 a.m. and 23 is 11:00 p.m. Calculate the average energy consumption for weekdays in a week for all circuits (Worksheet: “Step 4. Results,” cell D3.) $$\begin{array}{}\text{(53)}& {\overline{kWh}}_{WdCT}=\frac{\sum _{n=2}^6{\overline{kWh}}_{d,w}}{5}\end{array}$$ Where, ${\overline{kWh}}_{WdCt}=$ Average energy on a weekday (in kWh) ${\overline{kWh}}_{d,w}=$ Average hourly energy for each n weekday of the week (in kWh) $n=$ Day of week (2 = Monday, 3 = Tuesday, ..., 6 = Friday) $24=$ Hours per day Calculate the average energy consumption for weekend days in a week for all circuits (Worksheet: “Step 4. Results,” cell D6.) $$\begin{array}{}\text{(54)}& {\overline{kWh}}_{WEdCT}=\frac{{\overline{kWh}}_{1,w}+{\overline{kWh}}_{7,w}}{2}\end{array}$$ Where, ${\overline{kWh}}_{WEdCT}=$ Average energy on a weekend day (in kWh) ${\overline{kWh}}_{d,w}=$ Average hourly energy of each circuit for each n weekend day (in kWh) $n=$ Day of week (7 = Saturday, 1 = Sunday) $24=$ Hours per day Calculate the total annual weekday energy consumption (Worksheet: “Step 4. Results,” cell E3.) $$\begin{array}{}\text{(55)}& {\overline{kWh}}_{WdYr}={\overline{kWh}}_{Wd}\ast (261weekdaysperyear-X)\end{array}$$ Where, ${\overline{kWh}}_{WdYr}=$ Annual weekday energy consumption (in kWh) ${\overline{kWh}}_{Wd}=$ Average weekly weekday energy consumption (in kWh) $X=$ Number of weekdays that are considered holidays and adjusted to weekend day average energy consumption Calculate the total annual weekend day energy consumption (Worksheet: “Step 4. Results,” cell E6.) $$\begin{array}{}\text{(56)}& {\overline{kWh}}_{WEdYr}={\overline{hWh}}_{WEd}\ast (104weekenddaysperyear+X)\end{array}$$ Where, ${\overline{kWh}}_{WEdYr}=$ Annual weekend day energy consumption (in kWh) ${\overline{kWh}}_{WEd}=$ Average weekly weekend day energy consumption $X=$ Number of weekdays that are considered holidays and adjusted to weekend day average energy consumption Calculate total annual estimated energy consumption. $$\begin{array}{}\text{(57)}& {\overline{kWh}}_{ann}={\overline{kWh}}_{WdYr}+{\overline{kWh}}_{WEDYr}\end{array}$$ Where, ${\overline{kWh}}_{ann}=$ Annual energy consumption (in kWh) ${\overline{kWh}}_{WdYr}=$ Annual weekday energy consumption (in kWh) ${\overline{kWh}}_{WEdYr}=$ Annual weekend day energy consumption (in kWh) Equation (26) is the annual energy consumption of the measured circuits for a panelboard. If additional circuits were measured for the same panelboard with a different data logger be sure to consolidate the results (annual energy consumption) to obtain the total panelboard annual energy consumption. Additionally, if multiple panelboards were measured be sure to sum up the annual consumption of all panelboards to obtain the total system energy consumption. Lighting Inventory and Operating Schedule The following equations are used to calculate the annual energy consumption of a lighting fixture system. This methodology does not require electrical measurements, only lighting runtime (operating schedule) of the fixtures. Runtime data is collected with a light logger that detects when a light source turns on and off. If multiple fixture types operate with the same schedule the same runtime data can be used for calculations. This calculation tool can be used for different fixture types within a single space. For example, an office space with five different types of fixtures. The number of fixtures of each type must be known as well as the respective power draw (refer to the manufacturer specifications of the lamps and ballasts). Calculate power draw of the fixture type. $$\begin{array}{}\text{(58)}& k{W}_{fix1}=\frac{N\ast W_{fix1}}{1000}\end{array}$$ Where, $k{W}_{fix1}=$ Total power draw of single fixture type 1 (in kW) $W_{fix1}=$ Wattage of fixture type 1 (in W) $N=$ Number of fixtures of that type with the same operating schedule Convert fixture runtime measurements from seconds per hour to percent per hour (Worksheet: “Step 2. Percent Runtime Calcs”). $$\begin{array}{}\text{(59)}& {\mathrm{\%}}_{int}=\frac{t_{int}}{3600}\end{array}$$ Where, ${\mathrm{\%}}_{int}=$ Percent per hour the fixtures are on $t_{int}=$ Measured number of seconds the fixtures are on in each hour interval (in seconds) $3600=$ Constant, number of seconds in one hour Find the hourly average percentage for each day of the week the fixtures are on (Worksheet: “Step 3. Daily Avg Runtime Calcs”). $$\begin{array}{}\text{(60)}& {\mathrm{\%}}_{hourly}=\frac{\sum _1^n{\mathrm{\%}}_{int,n}}{n}\end{array}$$ Where, ${\mathrm{\%}}_{hourly}=$ Hourly average percentage the fixtures are on ${\mathrm{\%}}_{int}=$ Percent per hour the fixtures are on $n=$ Number of data points that have the same hour of day and day of week Sum of runtime percentages for a given day of the week to determing the operating hours for that day (Worksheet: “Step 4. Results”). $$\begin{array}{}\text{(61)}& {\mathrm{\%}}_{daily}=\sum _{h=0}^{23}{\mathrm{\%}}_{hourly,h}\end{array}$$ Where, ${\mathrm{\%}}_{daily}=$ Daily average hours the fixtures are on ${\mathrm{\%}}_{hourly}=$ Hourly average percentage fixtures are on $h=$ Hour of the day where 0 is 12:00 a.m. and 23 is 11:00 p.m. Convert percentage to hours to determing hours per day fixtures are on in space being measured (Worksheet: “Step 4. Results”). $$\begin{array}{}\text{(62)}& T_{daily}=\frac{{\mathrm{\%}}_{daily}}{100}\end{array}$$ Where, $T_{daily}=$ Number of hours the fixtures are on for a given day (in hours) ${\mathrm{\%}}_{daily}=$ Daily average hours in percent per day the fixtures are on Calculate the average energy use per weekday (Worksheet: “Step 4. Results”). $$\begin{array}{}\text{(63)}& {\overline{kWh}}_{Wd,fix1}=\frac{\sum _{d=2}^6{T}_{Wd,fix1,d}}{5}\ast k{W}_{fix1}\end{array}$$ Where, ${\overline{kWh}}_{Wd,fix1}=$ Average energy consumption during weekdays for fixture type 1 (in kWh) $k{W}_{fix1}=$ Total power draw of single fixture type 1 (in kW) $T_{Wd,fix1,d}=$ Number of hours the fixtures are on for a given d weekday (in hours) $d=$ Day of week (2 = Monday, 3 = Tuesday, ..., 6 = Friday) Calculate the average energy use per weekend day (Worksheet: “Step 4. Results”). $$\begin{array}{}\text{(64)}& {\overline{kWh}}_{WEd,fix1}=\frac{T_{We,fix1,1}+T_{We,fix1,7}}{2}\ast k{W}_{fix1}\end{array}$$ Where, ${\overline{kWh}}_{WEd,fix1}=$ Average consumption during weekend days for fixture type 1 (in kWh) $k{W}_{fix1}=$ Total power draw of single fixture type 1 (in kW) $T_{We,fix1,d}=$ Number of hours the fixtures are on for a given d weekend days (in hours) $d=$ Day of week (7 = Saturday, 1 = Sunday) Calculate the annual weekday energy consumption for the fixture type (Worksheet: “Step 4. Results”). $$\begin{array}{}\text{(65)}& {\overline{kWh}}_{WdYr,fix1}={\overline{kWh}}_{Wd,fix1}\ast (261weekdaysperyear-X)\end{array}$$ Where, ${\overline{kWh}}_{WdYr,fix1}=$ Annual weekday energy consumption of fixture type 1 (in kWh) ${\overline{kWh}}_{Wd,fix1}=$ Average energy consumption during weekdays for fixture type 1 (in kWh) $X=$ Number of weekdays that are adjusted to use weekend day average energy consumption Calculate the annual weekend energy consumption for the fixture type (Worksheet: “Step 4. Results”). $$\begin{array}{}\text{(66)}& {\overline{kWh}}_{WEd,Yr,fix1}={\overline{kWh}}_{WEd,fix1}\ast (104weekenddaysperyear+X)\end{array}$$ Where, ${\overline{kWh}}_{WEdYr,fix1}=$ Annual weekend day energy consumption of fixture type 1 (in kWh) ${\overline{kWh}}_{WEd,fix1}=$ Average energy consumption during weekend days for fixture type 1 (in kWh) $X=$ Number of weekdays that are adjusted to use weekend average energy consumption Calculate total annual estimated energy consumption for the fixture type (Worksheet: “Step 4. Results”). $$\begin{array}{}\text{(67)}& {\overline{kWh}}_{ann,fix1}={\overline{kWh}}_{WdYr,fix1}+{\overline{kWh}}_{WEdYr,fix1}\end{array}$$ Where, ${\overline{kWh}}_{ann,fix1}=$ Annual estimated energy consumption of fixture type 1 (in kWh) ${\overline{kWh}}_{WdYr,fix1}=$ Annual weekday energy consumption of fixture type 1 (in kWh) ${\overline{kWh}}_{WEdYr,fix1}=$ Annual weekend day energy consumption of fixture type 1 (in kWh) If multiple fixture types were measured find the sum of the annual estimated energy consumption for all fixture types (Worksheet: “Step 4. Results”). $$\begin{array}{}\text{(68)}& {\overline{kWh}}_{ann}=\sum _{i=1}^n{\overline{kWh}}_{ann,fi{x}_n}\end{array}$$ Where, ${\overline{kWh}}_{ann}=$ Total annual energy of all measured fixture types (in kWh) ${\overline{kWh}}_{ann,fix1}=$ Annual estimated energy consumption of each measured fixture type (in kWh) $n=$ Number of fixture types measured Hourly Results Worksheet Measurement data that is input in the calculation tools is used to generate an hourly energy consumption schedule for each hour in each day of the week. The schedule exists in the “Hourly Results” worksheet that is included in all four calculation tools. This data is useful to estimate the heating and cooling effects. CUNY BPL calculation tools do not calculate heating or cooling interactive effects. Further Reading For general information on Option A M&V guides, please read section 4.2 (starts on page 23) of “M&V Guidelines: Measurement and Verification for Performance-Based Contracts Version 4.0” from the U.S. Department of Energy: https://www.energy.gov/sites/prod/files/2016/01/f28/mv_guide_4_0.pdf#page=23 Richman, EE. (October 2012) “Standard Measurement and Verification Plan for Lighting Retrofit Projects for Buildings and Building Sites.” Richland, WA: Pacific Northwest National Laboratory. Richman, EE. (February 2016) “Measurement and Verification of Energy Savings and Performance from Advanced Lighting Controls.” Richland, WA: Pacific Northwest National Laboratory. Footnotes We reccomend taking a sample of measurements and find the average. The average value will be used to calculate annual energy consumption. As an example, the Onset HOBO 4-channel analog logger can measure a sample of current data at a predefined interval known as the sampling interval. If the logging interval is set to one-hour and the sampling interval is set to one-second, the logger will measure current every second for one hour then determine the average. The average will be stored in the logger as the one-hour interval measurement. This process will continue every hour for the duration of the measurement period. ↩︎