Reading the Utility Power Bill
One of the key steps of sizing a solar power system is knowing the electricity usage to account for. A previous year of utility bills are a straightforward way to get the details. The information needed includes the kWh (energy charge) for each meter (main meter, optional heat meter), and the kW (peak demand), for each month.
There are several ways to get this information. 1) From each month's bill, note the kWh charged for each month, including metered heat or peak demand (if either), and the rates for each. 2) Take a photo or scan each side of a power bill that includes a monthly graph or summary and charges. 3) Ask the utility to email you a 12-month usage summary. Otherwise, we can look at copies of your bills in person.
You may include this information when you complete the solar project form.
Read the bill
Utility bills can be hard to understand. Check with your utility and on their web site for a guide to reading the bill (example). Most utilities now offer an online service. Register to get detailed access to your billing online.
Utility bill formats vary somewhat, but most read similarly and have similar service plans. The type of service is another key factor, as well as the rates that go with the service type.
An easy way to get a summary of your monthly usage (kWh) is from the graph found on some bills:
Alternatively, you can contact your utility and request a monthly summary of usage.
The typical residential service options in our area fit one of the following categories:
Residential or Total Electric rate (Standard) - these services are simply based on the amount of electricity used.
Electric Heat rate - like a standard residential rate, except electric heat circuits are metered separately and charged at a special rate. There are two utility meters installed.
Demand Service - reduced energy charge (lower rate); additional charge on peak demand and may include installation of a demand controller.
The savings solar provides by offsetting power from the grid correspond directly to the utility rates. Below, see our example for using a bill to figure out what rates are being paid.
Black Hills Energy customer with Demand Service.
To determine the total energy charge, divide the billed amount by the kWh. The rate might also be shown in the description line. Most regular rates are greater than ten cents per kWh.
Black Hills Energy customers: Cost Adjustment is a component of the energy charge. For example, $41.91 / 1,230 kWh = $0.034 rate for cost adjustment. The energy charge rate and cost adjustment rate combined come to about $0.055 per kWh. Alternatively, you can combined the charges and divide by the kWh for the same result.
Typical residential rates in our area are between $0.10 to $0.14 per kWh (before tax). In the above example for a demand service, the energy charge is approximately half of the normal rate. If demand charges apply in your situation, learn more about peak demand.