About & method

CalcMoon Energy is a small, single-purpose site: work out what electricity actually costs to run the things in your home. It is part of CalcMoon.

The formula

Every number on this site comes from one equation:

Cost = (watts ÷ 1,000) × hours × days × rate

Kilowatt-hours are watts divided by 1,000, times hours. Multiply by your rate per kWh and you have dollars. There are no fudge factors, no "typical household" multipliers, and no assumptions about your duty cycle — you supply the hours.

Where the wattage figures come from

The ranges shown on each page are drawn from manufacturer rating labels and the US Department of Energy's appliance energy data, cross-checked against Energy Star average annual consumption figures. They are typical ranges, not guarantees: a 2012 fridge and a 2024 fridge of the same size differ by more than any single manufacturer's range suggests.

Default electricity rate

We start at 16.5¢ per kWh, close to the US residential average. This matters more than anything else on the page, so change it to the blended rate from your own bill — total dollars divided by total kWh.

CO₂ estimates

Carbon figures use 0.386 kg CO₂ per kWh, the US grid average from EPA eGRID. Regions with heavy hydro or nuclear (the Pacific Northwest, parts of the Southeast) run well below that; coal-heavy regions run above.

What this site does not do

It does not store what you enter, and it does not upload anything to a server. All arithmetic happens in your browser. We do not sell or share personal data.