Calculating your bill
The charges do not depend on the size of your solar system once you have exceeded 10kW, and only apply if you are enrolled in Net Metering billing.
Assuming both of these are true, your standby charge would be
- $2.68 per kW of demand, less the distribution kWh charge:
- 2.1558 cents per kWh up to 800 kWh
- 1.2212 cents per kWh over 800 kWh
- $1.35 per kW of demand, less the transmission kWh charge of 0.97 cents/kWh
If we assume that in an average month you use 1,000 kWh from the grid*, and your peak monthly demand from the grid* is 10kW, your standby charges would be as follows:
Distribution standby charge:
2.68 x 10 kW = $26.80
- 0.021558 x 800 kWh = - $17.25
- 0.012212 x 200 kWh = - $ 2.44
Total = $ 7.11
Generation standby charge:
1.35 x 10 kW = $13.50
- 0.0097 x 1000 kWh = - $ 9.70
Total = $ 3.80
Grand Total: $10.91
This standby charge is in addition to the already calculated distribution and generation charges -- meaning your bill includes the line items for $17.25, $2.44, and $9.70 calculated above, but you aren't double-charged for them in the standby charge.
In addition, your Rider T1 charge would be the lesser of:
0.001770 x 1000 kWh = $1.77
0.255 x 10 kW = $2.55
*Usage from the grid vs actual usage
Note that Dominion Energy only sees your net usage and demand from the grid. From their Net Metering FAQ page (emphasis added):
Your electric bill does not show all of the energy your system produced. The energy you produce that is consumed by your home does not pass through the Dominion Energy meter. The net meter measures electricity that is delivered from Dominion Energy to you, and any electricity that is produced by you and returned to the electric grid. The net meter cannot measure the total amount of electricity produced by your system because your home or business uses the electricity produced by the system first, and that electricity does not go through the meter.
This means that if your home's peak demand is 12 kW at a time when your solar system is producing 2 kW, the demand charge assessed by Dominion Energy will be based on the net peak of 10 kW.
As with all questions about electric rates and incentive programs in the U.S., I started with a look at the Database of State Incentives for Renewables & Efficiency. Their page on Net Metering in Virginia led me through a broken link which I finally resolved to the Net Metering FAQs on Dominion Energy Virginia's website, where I found this explanation:
What is the Standby charge?
The standby charge only applies to Net Metering customers served on Virginia Residential Schedule 1 with a generation system size in excess of 10 kW AC.
Residential customers served under Virginia Schedule 1 normally pay for electric system capacity (or electric system demand) through their kilowatt hour rate. This is different from other rate schedules that have a separate demand charge component in the rate.
The standby charge is based on the customer’s generation system size and the customer’s net energy consumption. The standby charge consists of a distribution standby charge, an electricity supply service (transmission) standby charge, and a Rider T1 standby charge. Refer to Virginia Residential Schedule 1 for more details.
Here are the details from Virginia Residential Schedule 1 (pdf):
Distribution Service Charges:
Plus, where the Customer receives service in accordance with Paragraph XXV – NET METERING of the Company’s TERMS AND CONDITIONS and where the alternating current capacity of the Renewable Fuel Generator exceeds 10 kW, the Customer shall be billed a Distribution Standby Charge of $2.68 per kW of demand, minus the charge under II.A.2.,
above, but not less than zero.
II.A.2. is the Distribution kWh charge -- 2.1558 cents per kWh for the first 800 kWh, and 1.2212 cents per kWh for each additional kWh.
Electricity Supply Charges:
Plus, where the Customer receives service in accordance with Paragraph XXV – NET METERING of the Company’s TERMS AND CONDITIONS and where the alternating current capacity of the Renewable Fuel Generator exceeds 10 kW, the Customer shall be billed a Transmission Standby Charge of $1.35 per kW of demand, minus the charge under II.B.2.a., above, but not less than zero.
II.B.2.a. is the Transmission kWh charge -- 0.97 cents for each kWh.
In the same rate schedule the Rider charges are mentioned:
Plus, where the Customer receives service in accordance with Paragraph XXV – NET METERING of the Company’s TERMS AND CONDITIONS and where the alternating current capacity of the Renewable Fuel Generator exceeds 10 kW, each measured kW of Demand is subject to all applicable riders, included in the Exhibit of Applicable Riders.
The applicable rider in this case is Rider T1 - Transmission (pdf). The Electricity Supply kWh Charge is 0.1770 cents per kWh, and the Demand Charge is $0.255/kW. The footnote on this schedule says:
Applied to kW of Demand only for net-metering applications where generation is sized above 10 kW. Such installations will pay the Rider T1 energy charge or the
Rider T1 demand charge, whichever is less.