Time-of-use rate calculator
The US average was 874 kWh a month in 2025.
From a smart meter or an online usage chart. 30 is an example.
Use the price from your bill if you know it.
Time-of-use minus flat.
One month on each plan
If your peak share is below the break-even figure, the time-of-use plan is cheaper for this month, ignoring fixed-charge differences.
The peak and off-peak prices shown are examples. Use the prices and hours in your utility's rate schedule, and the peak share from your own meter data.
How the comparison works
- Split your monthly kWh into the part used in the peak window and the part used outside it.
- Multiply each part by its price per kWh, and add any difference in fixed charges.
- Compare the total with what the same kWh would cost at the flat price.
The break-even peak share is the share of use at which both plans cost the same: the flat price minus the off-peak price, divided by the peak price minus the off-peak price. Below it the time-of-use plan wins, above it the flat plan does.
A worked example
Take a home using 874 kWh a month, the 2025 US average, a flat price of 17.23 cents, and a time-of-use plan with a 26 cent peak and an 11 cent off-peak price. Both prices are examples, not a real plan.
| Share of use at peak | Flat plan | Time-of-use plan | Difference |
|---|---|---|---|
| 20 percent | $150.68 | $122.40 | Saves $28.28 |
| 30 percent | $150.68 | $135.52 | Saves $15.17 |
| 40 percent | $150.68 | $148.63 | Saves $2.05 |
| 50 percent | $150.68 | $161.75 | Costs $11.06 |
| 60 percent | $150.68 | $174.86 | Costs $24.18 |
Source: Flat price: 17.23 cents per kWh, the 2025 US residential average from EIA Form EIA-861. Use: the 2025 US average. The time-of-use prices are invented for the example.
How to find your peak share
- Look in your utility account for hourly or 15 minute usage. Many smart meter accounts show a chart or a download.
- Read the plan's rate schedule for the peak hours and days, since peak often runs weekday afternoons and evenings and can change by season.
- Add the kWh in the peak hours and divide by your total for the period.
- If you cannot get hourly data, estimate from habits: cooking, laundry, air conditioning and charging an electric car in the evening all land in a common peak window.
What shifting use can do
On a plan with a wide gap between peak and off-peak, moving a few kWh a day can matter. Running the dishwasher and laundry later, pre-cooling the house before the peak and charging an electric car overnight are the usual moves. The EV charging cost pages and the appliance cost pages show what each costs to run. Read time-of-use rates explained for the full picture.
What the calculator leaves out
- Seasonal prices and shoulder periods. Enter an average if your plan has more than two prices.
- Demand charges, minimum bills and tiered prices. See demand charges explained.
- Changes in your behavior. A plan only helps if you can live with the hours it rewards.
Frequently asked questions
How do I know if a time-of-use plan will save me money?
Compare your peak share with the break-even peak share. If you use less of your electricity in the peak window than the break-even figure, the time-of-use plan costs less.
What is a peak share?
The percent of your monthly kWh used during the peak hours in the plan. Smart meter data or the plan’s hours and your habits give an estimate.
Do time-of-use plans cost more in summer?
Often peak prices are higher in summer, and the peak hours can differ by season. Run the calculator once with the summer prices and once with the winter prices.
Does this tool store my usage?
No. It runs in your browser and nothing you enter is sent to our servers.