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 18.31¢ per kWh that is $2.20 a day, and $65.92 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
- July 2026 (compared with July 2025)
- Released by EIA
- Sep 24, 2026
- Imported
- Oct 22, 2026
- Next EIA release
- Oct 23, 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.
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
- U.S. EIA: Electric Power Monthly, Table 5.6.A: Average price of electricity by state, July 2026 (released Sept 24, 2026)
- Virginia Cooperative Extension (Virginia Tech): Energy Series: Estimating Appliance and Home Electronic Energy Use (BSE-301), reproducing DOE's typical appliance wattage table
- Sunbeam: Brushed Fleece Grey Heated Blanket, Queen (item 13702) product specifications
- Sunbeam: Microplush Poseidon Heated Blanket, Queen product specifications
- Sunbeam: Heated Bedding instruction manual (Sunbeam Canada)
- U.S. DOE: Energy Saver Guide (2022)
- U.S. EIA: FAQ: How much electricity does an American home use?
- U.S. CPSC: Staff Assessment on Portable Electric Heaters (Feb 2023)
- Lasko 754200 ceramic heater, manufacturer specifications
- U.S. DOE: Home Heating Systems fact sheet
- U.S. CPSC: Space heater, furnace and fireplace safety warning
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.
Found a mistake? wattcost@mail.grokbot.com