All 29 Free Home Energy Calculators
Every formula shown. Every source cited. No email required. Six categories covering electricity, heating, cooling, solar, EV charging, appliances, and insulation — with verified data for the US, UK, Canada, and Australia.
Electricity
Heating & Cooling
Solar
Appliances
Insulation & Windows
How to choose the right calculator
Not sure where to start? Pick the category that matches what you're trying to understand:
- Trying to lower your overall electricity bill? Start with the Electricity Bill Calculator to break down where your kWh are going, then use the Phantom Load Calculator to identify standby waste.
- Considering solar? The Solar Payback Calculator tells you how long until your panels pay for themselves. The Panel Size Estimator tells you how big a system you need.
- Switching to electric heating? The Heat Pump vs Furnace Calculator shows the running cost difference using your local rates.
- Buying an electric car? The EV Home Charging Cost Calculator estimates your monthly charging bill before you sign on the dotted line.
- Wondering what a single appliance costs? The Appliance Energy Cost Calculator works for any device with a known wattage.
What makes a KilowattKit calculator different
Every calculator on this site has to pass the same five-part standard before it is published:
- Visible formula. The exact maths is shown on the page in plain text. No black-box calculations.
- Named assumptions. Every input that uses a default value is identified and explained.
- Cited sources. Every numerical default links to the official source it came from, with a "last verified" date.
- Worked example. Each calculator includes a worked example with realistic inputs so you can verify the output by hand.
- Scope statement. We explicitly state what each calculator does NOT include — for example, tiered rates, demand charges, or regional rebates.
See our Methodology page for the full standard, our six-step research process, and our update schedule.
Common questions
Are these energy calculators really free?
Yes — all 29 calculators are free, with no signup, no email capture, and no paywall. Results appear instantly in your browser. We are supported by display advertising and, on some pages, affiliate links to solar quote services or smart thermostat retailers. Affiliate links never affect calculator outputs, defaults, or methodology, and are disclosed on every page where they appear.
What countries do the calculators support?
All KilowattKit calculators support the United States (EIA rates), United Kingdom (Ofgem), Canada (Natural Resources Canada), and Australia (Australian Energy Regulator). Most calculators include a country picker that loads the correct default electricity rate, currency, and units for your region. You can also override the rate with your actual figure from your bill for personalised results.
How accurate are the calculator results?
Our calculators are estimates, not guarantees. Accuracy depends on the quality of the inputs you provide — if you enter your actual rate per kWh from your bill, results are typically within 5-10% of the real cost. If you use the default average rate, results are accurate for an average household in your country but may differ from your specific bill due to time-of-use tariffs, demand charges, or regional variations.
Where does your data come from?
Electricity and gas rate defaults come exclusively from official regulators: the EIA Electric Power Monthly (US), Ofgem (UK), Natural Resources Canada and the Canada Energy Regulator (Canada), and the Australian Energy Regulator (Australia). Appliance wattages and equipment efficiency figures come from ENERGY STAR, the US Department of Energy, EPA fueleconomy.gov, and manufacturer specification sheets. See our Data Sources page for the complete list with verification dates.
How often are the calculators updated?
Electricity and gas rate defaults are reviewed and updated quarterly. Government grant pages are updated whenever programme details change (often more than quarterly). Equipment wattage and efficiency figures are reviewed annually. Every calculator carries a "Last verified" date on the page, and we log all material changes on our Updates page.