About Home Energy Calculators

Our Mission

We believe households spend tens of thousands of dollars on energy equipment with little independent information before signing a contract. Installer quotes often arrive without showing the underlying math — system size, expected production, payback period, or backup runtime.

Home Energy Calculators closes that gap. Every calculator publishes its formula on the same page as the result, so you can recompute by hand, compare quotes from multiple installers, and walk into a sales conversation already knowing the rough answer.

What We Cover

The site currently offers 14 calculators across four planning domains: EV charging (charge-time, road-trip stops, lease vs buy, total cost of ownership), solar sizing (panel count, payback period, net metering savings, tilt and azimuth, inverter and DC current sizing), battery and backup (portable power station or UPS runtime, whole-home backup coverage, standby generator sizing), and home energy upgrades (heat pump vs gas furnace, wind turbine annual energy).

Each calculator runs entirely in your browser — there is no account, no upload, and no server-side processing of your inputs.

Our Methodology

Formulas are drawn from public, well-documented sources: NREL PVWatts for solar derating, EV manufacturer charge-curve disclosures for AC and DC fast charging, NEC 2023 derating factors for inverter and conductor sizing, U.S. EIA national average rates as the default electricity price, and Battery Council International depth-of-discharge guidance for lead-acid and LiFePO4.

Defaults are intentionally conservative — for example, 78% PVWatts system loss, 90% AC charging efficiency, 85% inverter round-trip efficiency, and 80% lithium DoD. You can override every default to match your local data sheet, climate, and utility tariff.

How To Use the Results

Treat every output as a planning estimate, not an engineering specification. The calculators model the dominant physics (Ohm’s law, energy conservation, charge taper, depth of discharge), but they do not replace a site survey, a structural review of your roof, a panel-by-panel shade analysis, a National Electrical Code permit review, or a utility interconnection study.

Before purchasing or installing any equipment, verify against the product manual, the installer’s engineered drawings, your utility’s interconnection and net-metering rules, and your local electrical and building codes.

Independence

We do not accept paid placement, paid reviews, or affiliate revenue on calculator results. Equipment models named in worked examples (Tesla Model Y, EcoFlow Delta 2, Ford F-150 Lightning, APC Smart-UPS, etc.) are mentioned solely because they are well-known reference points; we have no commercial relationship with the manufacturers.

The codebase is small enough that the formulas are auditable end-to-end. If you spot an error or want to suggest a new calculator, we would like to hear from you.

Contact

Reach the maintainer at [email protected]. Bug reports, corrections, and requests for new calculators are all welcome.