If you receive only a net-metered bill from your utility, meaning your bill only shows the difference between the energy you imported from the grid minus the energy you exported (C – A in the diagram below), then you’ll need to calculate the values for A, B, and C below using your bill and your organization’s internal records.
As explained in Part 2 of this FAQ, three values are required if you have onsite green power:
- A: The energy you generated onsite and exported to the grid
- B: The energy you generated onsite and used onsite
- C: The energy you purchased from the grid
If you have a net metering setup, you may not have access to A, B, and C. But, you may have access to:
- G (Generated): Total onsite energy generated, G = A + B
- N (Net): Total net energy from the grid, N = C - A
Below is an example of calculating A, B, and C, when your energy bills are net-metered.
Value A: The energy you generated onsite and exported to the grid. Get this value from your utility bill (or from your organization’s data logs), and enter it in the “Energy Exported Offsite” column for your Onsite Green Power meter, as shown below. In this example, the value is 50 kWh and comes from the utility bill.
Value B: The energy you generated onsite and used onsite. Take value G (Generated) that you obtained from onsite measurements of energy production (in this case 1,000 kWh) and subtract A (50 kWh), then enter the result in the “Energy Used Onsite” column of your onsite meter, as shown below (950 kWh).
Value C: The energy you purchased from the grid. Take value N from your utility bill (25 kWh), and add A (50 kWh) to calculate the total amount of energy the building used that was physically supplied by the grid (75 kWh). Input this value in your Electric Grid meter.
Note: It may be helpful to set up formulas to run these calculations within a spreadsheet file so you don’t need to repeat the calculation manually each month.