Home Energy and Sustainability Calculators
Four calculators that put a dollar figure and a carbon figure on the biggest household energy choices: rooftop solar, home battery backup, switching to an electric car, and where your household’s emissions actually come from.
4 calculators · Last reviewed September 26, 2026
The calculators
Which calculator answers your question?
How many years until solar panels pay for themselves?
Solar PaybackHow much would I save on fuel by driving electric?
EV SavingsWhere does most of my household’s carbon footprint come from?
Carbon FootprintHow big a home battery do I need to ride out a power outage?
Home Battery BackupKey ideas behind these calculators
Simple payback
Payback in years is the net installed cost divided by the yearly savings. It ignores financing and future rate changes, so treat it as a first filter. Panels usually carry 25-year performance warranties, so a payback well inside that window leaves years of low-cost power afterward.
Cost per mile
A gas car costs gas price ÷ miles per gallon per mile. An EV costs electricity price ÷ miles per kWh. Your local electricity rate and how much you charge at home versus at public fast chargers swing the result more than anything else.
Emission factors
A carbon footprint is activity × emission factor, summed across electricity, driving, flights and diet. Electricity factors vary widely by region because some grids run on far more coal and gas than others.
Federal credits have ended
The 30% residential clean energy credit (Section 25D) does not apply to systems paid for after December 31, 2025, and the clean vehicle credit (Section 30D) ended for vehicles acquired after September 30, 2025. State and utility rebates may still apply.
What these estimates leave out
- Net-metering rules, time-of-use rates and utility fees, which differ by state and utility.
- Battery degradation, maintenance, insurance and financing costs, unless you enter them.
- Manufacturing (embodied) emissions of panels, batteries and vehicles.
See the full disclaimer and how we build and check the calculators.
Sustainability guides
All guidesSection 25D Solar Tax Credit Ended: What's Left in 2026
The 30% credit for homeowner-owned solar and batteries ended for installs completed after Dec 31, 2025. What that does to payback and what remains.
4 min read · Updated Sep 26, 2026
Net Zero Home Upgrades: What to Do First in 2026
Seal and insulate first, then heating and cooling, then solar sized to the smaller load. The order, the 2026 tax credit changes, and a sizing example.
4 min read · Updated Sep 26, 2026
Is a Home Battery Worth It in 2026? Sizing and Payback
Home batteries installed after 2025 get no federal credit. How to size one for outages and estimate payback from bill savings, with the math shown.
4 min read · Updated Sep 26, 2026
Does Remote Work Reduce Your Carbon Footprint?
Usually yes, if it replaces a car commute. A worked example weighs commute savings against extra home energy, plus what research found about hybrid work.
4 min read · Updated Sep 26, 2026
EV vs. Gas Car Savings in 2026: Break-Even and Range
At 2026 U.S. average prices, home charging costs about 5 cents a mile vs. 18 for a 25 mpg car. How to find your break-even now the EV credit is gone.
4 min read · Updated Sep 26, 2026
How to Cut Commute Emissions: Car, EV, Transit or Bike
Transportation is the largest U.S. emissions source. Compare fewer trips, an EV, transit and biking for a 12-mile commute, with the math shown.
4 min read · Updated Sep 26, 2026