How to use the net metering bill calculator
- Pick how credits are handled: banked as kWh, banked as dollars, or not carried over.
- Enter your price per kWh bought, the credit per kWh sent (when credits are in dollars) and the fixed charge per month. The values shown are examples.
- Fill in the kWh bought and kWh sent for each month, taken from your bills.
- Read the total of the 12 bills, the energy and fixed charges, the credit left in December and the month-by-month table.
Formula
kWh banked: energy charge = max(0, bought - sent - banked kWh) x price; banked kWh = max(0, sent + banked - bought)
Dollars banked: credit = sent x credit rate; energy charge = max(0, bought x price - credit - banked dollars)
No carry over: energy charge = max(0, bought x price - credit)
bill = energy charge + fixed charge
Banked amounts start at zero in the first month. This page uses a calendar year starting in January.
A year with strong summer exports
Bought: 900, 780, 650, 520, 430, 480, 590, 610, 470, 500, 700, 880 kWh. Sent: 20, 60, 300, 500, 700, 800, 750, 700, 500, 300, 40, 10 kWh. Price $0.15 per kWh and fixed charge $12.
With credits banked as kWh, the bills total $568.50 and the bank peaks at 870 kWh in September. With credits banked as dollars at $0.08 per kWh the total is $896.10. At $0.20 per kWh the total is $417.50 and $83.00 of credit is still left after December. With no carry over at $0.20 the total is $659.50 and $325.00 of credit is lost. Without any exports the year would cost $1,270.50.
Three ways credits can work
Under one common arrangement, each kWh you send offsets one kWh you buy at the same price, and extra kWh are banked for later months. Under another, exports earn a credit in dollars at a rate that may be lower than the price you pay, and the money is banked. A third arrangement credits exports only against the same month. Which one applies to you, and what happens to unused credits at the end of a year, is set by your utility and your contract. This page lets you try each rule on your own numbers.
To judge whether solar pays back, see the solar payback calculator. To size the strings that feed an inverter, use the solar string sizing calculator, and for a single load use the electricity cost calculator.
What is not included
Time-of-use pricing, demand charges, tiered rates, taxes, minimum bills and annual true-ups differ by utility and change over time, so none of them are applied. Enter a single average price per kWh that matches your bill, or run the page twice with two prices to bracket the result. The result describes the numbers you enter and is not a quote.
Assumptions and limits
- The price per kWh, credit rate and fixed charge are example values until you replace them with your own.
- One price applies to every month. Seasonal or time-of-use rates are not modeled.
- Banked kWh or dollars start at zero in January and carry forward through December. What happens to a bank at the end of the year is shown but not paid out.
- Energy bought and sent are measured at the meter in whole or decimal kWh.
Frequently asked questions
What is the difference between net metering and net billing?
Net metering usually credits each exported kWh at the same price as a bought kWh. Net billing credits exports at a separate rate, often lower, in dollars. This page models both with the credit options.
Why does a larger bank not always save more?
Banked credits only help in months when you buy more than you send. If the bank is still large after December and the utility resets it, those credits are worth little or nothing, as the lost-credit line in the no-carry-over option shows.
Where do I find kWh bought and sent?
Most utility bills list both numbers per month, often called delivered and received, or imported and exported. An online account usually shows the history for the past year.
Does the result include solar equipment cost?
No. It only turns monthly kWh into bills under a credit rule. Add equipment, financing and maintenance separately when you judge a project.