Keep honest books on your energy.
Free calculators for solar, EV and home-energy decisions. Drive them with your own numbers and see the payback, savings and running cost — with the formula and sources shown in full.
Total saved
$7,480
- Annual fuel saving
- $1,496
- Break-even
- 4.2 yrs
- CO₂ avoided / yr
- 2.7 t
- Cost per mile
- 4.3¢
Sample figures for illustration. Run the EV vs gas calculator with your own inputs.
Pick a calculator
Eight tools across solar, EV and whole-home energy.
Solar savings & ROI
Payback period, 25-year savings and ROI for a rooftop solar system.
Open calculator →SolarSolar system size
How many panels and how much roof you need to cover your usage.
Open calculator →EVEV vs gas cost
Total cost of ownership, break-even mileage and CO₂ saved.
Open calculator →EVEV charging cost
Cost per charge, per mile and per month at your electricity rate.
Open calculator →EVEV charging time
How long to charge between two states of charge at a given power.
Open calculator →HomeHeat pump savings
Annual savings vs your current heating fuel, payback and CO₂ cut.
Open calculator →HomeHome battery payback
Annual savings, payback period and lifetime value of storage.
Open calculator →HomeElectricity bill
Daily, monthly and annual running cost for any appliance.
Open calculator →Private by default
Every calculation runs in your browser. No inputs are sent anywhere and nothing personal goes in a URL.
Transparent methodology
Each tool shows its formula, every default value and the dated source behind it. No magic numbers.
Estimates, not advice
Results are estimates to inform your own research — not financial, tax or engineering advice.