What does time-of-use electricity cost?

People type this into search every day: time of use electricity calculator.

The usual answer is “power is cheaper at night.” That is the right story. You still need the kWh in each window, two prices, and the fixed charge that does not move.

This page is a labeled bill. It is not your utility tariff, and it is not a demand-charge model.

Two prices, one month

The EIA does not publish peak and off-peak retail rates. Their FAQ says so in those words. What they do publish is the average you already know from a flat bill.

Their prices and factors page puts the 2025 US residential average at 17.30 cents / kWh. The same page says some utilities offer time-of-day pricing because wholesale cost is higher in the afternoon. The EIA Electricity Monthly Update later printed 18.31 cents / kWh as US residential average revenue in July 2026. Neither number is a peak price. Type the two lines from your tariff.

The time-of-use energy cost calculator uses:

peak use × peak rate + off-peak use × off-peak rate + fixed charge

All usage fits one of the two periods. Demand charges and taxes are excluded. Those are the tool’s assumptions.

The Department of Energy appliance energy page is the kWh method underneath: watts × hours ÷ 1,000. Split those hours into the two windows if your tariff does.

Example 1: the published $153 month

Here are the calculator defaults:

• peak-period use: 220 kWh
• peak price: $0.34 / kWh
• off-peak use: 430 kWh
• off-peak price: $0.14 / kWh
• fixed monthly charge: $18

Peak cost: 220 × 0.34 = $74.80

Off-peak cost: 430 × 0.14 = $60.20

Usage: 74.80 + 60.20 = $135.00

Month: 135 + 18 = $153.00

Blended usage rate: 135 ÷ 650 = $0.2077 / kWh

The blended $0.2077 is not a third tariff. It is the usage pile divided by 650 kWh. Move a kilowatt-hour and the blend moves.

A year of that month, with no seasonal change, is 153 × 12 = $1,836.00.

Example 2: what if I move 100 kWh off the peak

Hold the two prices and the $18. Shift 100 kWh from peak to off-peak.

• peak: 120 kWh
• off-peak: 530 kWh

Peak: 120 × 0.34 = $40.80

Off-peak: 530 × 0.14 = $74.20

Month: $133.00

Blended usage rate: $0.1769 / kWh

The month dropped $20. That is 100 × (0.34 − 0.14). The fixed $18 cancelled out.

A year of that shift is 20 × 12 = $240.00. Same house, same 650 kWh.

Example 3: every kilowatt-hour on-peak

650 kWh at $0.34, nothing at night.

Peak: 650 × 0.34 = $221.00

Month: $239.00

Blended usage rate: $0.34 / kWh

This is the “I run the dryer at 5 pm” bound. It is $86 more than the default split.

Example 4: every kilowatt-hour off-peak

650 kWh at $0.14.

Off-peak: 650 × 0.14 = $91.00

Month: $109.00

Blended usage rate: $0.14 / kWh

All-peak minus all-off-peak is 239 − 109 = $130.00. The $18 is in both months. The swing is 650 × 0.20.

Example 5: a higher peak price

Keep 220 / 430 kWh and $18. Raise only the peak price to $0.48.

Peak: 220 × 0.48 = $105.60

Month: $183.80

Blended usage rate: $0.2551 / kWh

That is $30.80 above the default, which is 220 × 0.14. Off-peak did not move.

Example 6: a small apartment

• peak: 80 kWh
• off-peak: 180 kWh
• fixed: $12

Peak: $27.20

Off-peak: $25.20

Month: $64.40

Blended usage rate: $0.2015 / kWh

260 kWh at the default 650-kWh blend of $0.2077 would have been 260 × 0.2077 + 12 = $66.00. Close. The apartment uses a slightly smaller peak share, 80 / 260 = 30.8% against the default 220 / 650 = 33.8%.

Example 7: a larger house

• peak: 400 kWh
• off-peak: 700 kWh
• fixed: $22

Peak: $136.00

Off-peak: $98.00

Month: $256.00

Blended usage rate: $0.2127 / kWh

A year is 256 × 12 = $3,072.00. The default year was $1,836.00.

Example 8: the common mistake, treat the blend as a flat rate you can ignore

Someone reads $0.2077 and plans a new 200 kWh habit as 200 × 0.2077 = $41.54.

If those 200 kWh land on-peak, the extra cost is 200 × 0.34 = $68.00.

If they land off-peak, the extra cost is 200 × 0.14 = $28.00.

The blend was an average of hours you already used. It is not the price of the next hour.

Example 9: the same 650 kWh on a flat EIA-style rate

Put both windows at $0.1831, the July 2026 EIA residential average, and keep $18.

Peak: 220 × 0.1831 = $40.28

Off-peak: 430 × 0.1831 = $78.73

Month: $137.02

Blended usage rate: $0.1831 / kWh

The default TOU month was $153.00. The flat EIA-average path is $15.98 cheaper on this split. That is not a reason to switch tariffs. EIA’s own FAQ says they do not publish your peak price. The $0.34 / $0.14 pair is a planning pair.

The electricity bill estimate calculator is the flat-rate neighbor. Its defaults are 650 kWh at $0.22, $18 fixed, 5% tax: $169.05. Drop the tax and use the TOU blend of $0.2077, and that tool prints $153.01. The one cent is rounding on 650 × 0.2077.

Example 10: overnight EV charging on the default house

The home EV charging calculator default is 1,200 km, 18 kWh / 100 km, 10% loss: 237.6 kWh and $66.53 at $0.28.

Add 200 kWh of night charging to the TOU default, a round planning number next to that 237.6.

• peak: 220 kWh
• off-peak: 630 kWh

Month: $181.00

The extra 200 kWh cost 181 − 153 = $28.00, which is 200 × 0.14. Charge those 200 kWh on-peak and the extra is $68.00. The appliance electricity post is the same watts-and-hours method, without the two windows.

The ten months next to each other

Open the time-of-use energy cost calculator with the two prices from the tariff and the kWh in each window. If the bill is still one rate, use the electricity bill estimate. A single appliance inside one window belongs on the appliance electricity cost calculator.