Home energy · editable assumptions
Plan the energy, see the trade-offs.
Small calculators for household energy decisions. Bring your own rate, equipment label or production estimate; every result shows the formula and its limits.
Solar panel annual yield
Estimate yearly kWh from system kW, peak sun hours and system losses.
Solar payback
Model first-year value and payback from production, self-use, export credit and system cost.
EV home charger payback
Months to recover charger and install cost, plus yearly saving versus a gas car.
Appliance electricity cost
Turn watts, run time, quantity and your rate into monthly and annual cost.
Battery backup runtime
Estimate usable AC runtime after reserve and inverter losses.
Generator load & surge sizing
Add running and starting watts to check continuous and surge requirements.
Room AC BTU sizing
Size a room air conditioner from floor area using ENERGY STAR's chart and adjustments.
Heat pump savings
Compare annual heating cost and payback for a heat pump using HSPF2 or COP and your own prices.
Heating cost comparison
Cost per GJ and kWh of delivered heat for gas, propane, oil, electric, heat pump and wood.
ENERGY STAR certified lookup
Search the official certified-model index by brand or model number.
Water-heater recovery
Estimate how long a heater needs to raise a tank from inlet to target temperature.
What these estimates are for
These are planning tools, not engineering sign-off, utility-bill forecasts or equipment recommendations. Use the nameplate, utility tariff, installer quote and local code requirements for a purchase or installation decision.
Sources include NREL PVWatts, the U.S. EIA electricity measurement guide, Generac's wattage worksheet and DOE's water-heater test procedure.