Calculate Your Energy Savings
Make smarter energy decisions with our free, accurate calculators. From solar payback to EV charging costs—get the numbers you need in seconds.
Featured Calculators
Our most popular energy calculators to help you make informed decisions about efficiency and savings.
Solar Payback
Calculate how many years it will take for energy savings to equal the initial cost of your solar panel system.
Battery Storage
Size home battery systems, estimate backup duration, and calculate savings from solar self-consumption and time-of-use arbitrage.
Bill Estimator
Calculate your monthly electricity bill based on appliance usage with support for flat and tiered rate structures.
Water Heater
Compare operating costs between tankless, heat pump, and traditional tank water heaters for your household.
HVAC Sizing
Calculate the right size heating and cooling system for your home based on square footage, climate, and insulation.
Carbon Footprint
Estimate your annual CO2 emissions from electricity, gas, driving, and flights, with tips to reduce your impact.
Accurate calculations you can trust
WattMath provides transparent, methodology-backed calculators that help homeowners and professionals make data-driven energy decisions.
Transparent Methodology
Every calculation shows the formulas and assumptions used. No black boxes.
Local Cost Data
Input your actual utility rates for accurate savings estimates.
Instant Results
Get calculations in seconds, no signup required.
Ready to start saving?
Jump into our calculators and discover how much you could save on your energy bills.