Rate-plan fit
A time-of-use plan charges less off-peak and more at peak. It wins when your peak share is below a break-even level that depends on the two prices and any change in the fixed charge. Enter both plans to find yours.
Try it with your numbers
Prefilled prices are examples: the off-peak price is 15% below and the peak price 60% above your state's EIA average. Replace them with the rates on your plan sheets.
Monthly bill by peak share
Break-even peak share, five example plans
| Flat rate | Off-peak | Peak | Flat fee | TOU fee | Break-even share |
|---|---|---|---|---|---|
| 16¢ | 10¢ | 22¢ | $10 | $10 | 50% |
| 16¢ | 12¢ | 24¢ | $10 | $10 | 33% |
| 16¢ | 12¢ | 28¢ | $10 | $10 | 25% |
| 12¢ | 8¢ | 24¢ | $8 | $12 | 22% |
| 20¢ | 14¢ | 30¢ | $12 | $12 | 38% |
Example prices we chose, not any utility's plan. Below the break-even share the time-of-use plan is cheaper.
Where home customers are already on dynamic pricing
| State | Home customers enrolled | Utilities with TOU | Smart-meter share |
|---|---|---|---|
| California | 5,126,006 | 24 | 87% |
| Michigan | 1,755,647 | 12 | 97% |
| Maryland | 1,698,747 | 2 | 86% |
| Missouri | 1,521,174 | 6 | 88% |
| Arizona | 1,226,276 | 10 | 93% |
| Colorado | 1,207,135 | 18 | 92% |
| Oklahoma | 624,162 | 3 | 93% |
| Illinois | 518,810 | 7 | 94% |
| Texas | 338,156 | 14 | 95% |
| Delaware | 262,644 | 1 | 94% |
| Louisiana | 209,932 | 2 | 89% |
| New York | 181,494 | 3 | 74% |
Enrollment covers every dynamic program, not only time-of-use. Check your own utility's plan list and whether your meter can record hourly use.
The formula
Flat bill = flat fee + flat rate × kWh. Time-of-use bill = time-of-use fee + kWh × (off-peak rate + peak share × (peak rate − off-peak rate)). Setting both equal gives the break-even peak share. If it falls above 100% or below 0%, one plan wins at every peak share.
Sources
- Home price and use by state: U.S. EIA state electricity data, annual 2025; CSV: state-price-and-use-2025.csv.
- Dynamic pricing enrollment, utilities with time-of-use and smart-meter share: EIA-861, 2024 data year.
Keep going
- All bill tools
- Bill decoder
- True cost of power
- Time-of-use and tiered rates by utility
Questions
What counts as peak hours?
Each utility defines its own window, often late afternoon to evening on weekdays. Check the plan sheet and your meter data.
How do I find my peak share?
Many utilities show hourly use online. Add up the kWh in the peak window and divide by total kWh.
Do demand charges change the answer?
Yes. This tool covers energy rates and fixed fees only; a plan with a charge per kW needs your peak demand as well.