About WattCosts

WattCosts is a small collection of free home energy cost calculators. The goal is simple: answer "what does this cost to run?" quickly, with the formula shown and the data source named — no sign-up, no clutter.

Data sources

• Electricity rates: U.S. Energy Information Administration, Electric Power Monthly, Table 5.6.A — average residential retail price by state. The current dataset period is shown in the footer of every tool and the data is refreshed on a monthly schedule.
• Gas price default: AAA national average for regular gasoline, noted with its date wherever used.
• Typical device wattages: mid-range values from published measurement studies (including Lawrence Berkeley National Laboratory's standby power data) and manufacturer specifications. Every wattage field is editable, so measured values always win.

Method and transparency

Each calculator page includes a "How this is calculated" section with the exact formula used. All computation happens in your browser; the tools work offline once loaded and send nothing you type to any server.

Who runs this site

WattCosts is independently owned and operated by a private individual, built and maintained with the help of AI tooling. There is no company behind it, no sales team, and no sponsored rankings — the data sources and formulas cited above are the whole methodology. The site is monitored continuously: every page is health-checked monthly and the rate data is checked weekly for staleness.

Disclosure

The site is free to use and shows no display ads. Some pages contain clearly labeled affiliate recommendation boxes — see the affiliate disclosure for exactly how those work. Affiliate links never affect any calculator's results.

Contact

Found an error in a formula or a stale rate? Have a partnership inquiry? Contact the site owner — corrections are welcome and shipped quickly.