How we calculate costs

Every cost on WattCost comes from one formula and two published inputs. This page lists both, the assumptions we make, and where they fall short.

The formula

cost = watts × hours ÷ 1,000 × price per kWh

Watts ÷ 1,000 converts to kilowatts. Kilowatts × hours gives kilowatt-hours (kWh), the unit on your bill. kWh × your price per kWh gives dollars.

Example: a 1,500 W heater for 8 hours is 12 kWh. At 18.16¢ per kWh that is $2.18 a day, and $65.38 over 30 days.

Electricity prices

State and U.S. prices are EIA's average residential price: residential revenue divided by residential kWh sold in the month. That means the figure already includes delivery charges and other per-kWh costs, averaged across every utility in the state.

Source: U.S. EIA, Electric Power Monthly, Table 5.6.A (residential sector)
Data month: August 2026 (compared with August 2025)
Released by EIA: Oct 23, 2026
Imported: Oct 24, 2026
Next EIA release: Nov 24, 2026
Unit: cents per kilowatt-hour (¢/kWh), residential sector
License: EIA data is public domain. Our derived tables: CC BY 4.0

Assumptions

A month is 30 days of the same daily use. A year is 12 such months. Real use is seasonal, so a yearly figure is an upper bound for something you only run in winter.
Appliances draw their rated wattage the whole time they are on. Thermostats and low settings cycle the power, so real use is often lower. A plug-in energy meter shows the true kWh.
Prices are monthly state averages. Your utility, your plan and the season can put your price above or below the average.
Fixed monthly charges (customer or service fees) are not included, because they don't change with use.

Bitcoin mining pages

Mining income per day = hashrate (TH/s) × hashprice (dollars per TH/s per day). Hashprice = 144 blocks × (block subsidy + average fees per block over the last 144 blocks) × Bitcoin price ÷ network hashrate implied by difficulty, from the public mempool.space and CoinGecko APIs, checked against Hashrate Index. It is gross, before pool fees. Electricity a day = wall watts × 24 ÷ 1,000 × price. Breakeven price = income per day ÷ kWh per day. Hashrate and wall power are the maker's rated figures; real units vary by a few percent.

Rounding

Amounts under $100 are shown to the cent; larger amounts to the dollar. Percent changes are rounded to one decimal. Calculations use unrounded inputs.

Updates

EIA publishes new state prices around the 24th of each month. We import the new month after the release, rebuild every page, and update the CSV and the open dataset. Each page shows its data month and last-updated date.

Sources used across the site

Reuse and citation

Our tables are free to reuse under CC BY 4.0 with credit to WattCost and a link. Suggested citation and CSV: electricity prices by state.

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