About Home Kilowatt

Home Kilowatt is a catalog of the energy bills in your home: what each appliance costs to run, at your state's electricity rate and in your state's climate. Every calculator opens with working defaults, updates as you type and shows the formula it used.

Most answers online use a national average, a rate from years ago, or end in a quote form. Your state's rate can be more than three times another state's, and a heater costs nothing in July. The number should reflect both.

• Your state first. Each calculator starts from your state's average residential electricity rate from the U.S. Energy Information Administration (EIA) and shows the month the number comes from. You can always type the rate from your own bill.
• The formula is on the page. Constants come from primary sources: EIA, NOAA, DOE, ENERGY STAR, AHRI. We name the source next to each one.
• Tested before it ships. Every calculator is checked against three worked cases computed separately from the site's code. If the page doesn't return those numbers, it doesn't go live.
• Estimates, not promises. We show what something costs to run under the assumptions you can see. We don't promise savings.

• Electricity rates are refreshed monthly from the EIA.
• Every constant (wattages, efficiencies, degree-days) has a "last reviewed" date on its page.
• Every change to a constant or formula is logged with its date in the changelog.
• Rules that change, like federal and state incentives, are checked on a fixed schedule. The federal 25C and 25D credits ended for installations after Dec 31, 2025, and nothing on this site says otherwise.

Home Kilowatt is written and maintained by an independent editor, who reviews every formula and constant before it's published and answers every error report. The review method is the same for every page:

• Tested against worked cases. Each calculator must return the exact results of three worked cases computed by a separate reference implementation of the same formulas.
• Sourced and dated. Every constant names its source (EIA, NOAA, DOE, ENERGY STAR, AHRI) and every calculator page shows a "last reviewed" date.
• Logged. Every change to a rate, constant or formula goes in the changelog with its date.

The calculators are free. We show a small number of ads from Google AdSense, always outside the calculator itself and never next to its buttons. We don't sell leads, collect phone numbers or ask you to sign up.

Found a wrong number or a missing appliance? Email hello@homekilowatt.com. Corrections go in the changelog with the date.