Clean energy
EV charging cost calculators, state electricity comparisons, and solar payback modeling built on EIA and EPA data.
No sign-up. No data leaves your browser. Updated 2026.
Each tool includes a worked methodology, assumptions, and common pitfalls below the numbers.
Enter your annual mileage, local gas price, and residential electricity rate to calculate annual fuel savings, cost per mile, and 5-year total fuel costs.
Open calculator → EV chargingEnter your EV battery pack size (kWh) and starting and target charge percentages to compare charging hours and session costs across all three charging levels.
Open calculator → Home solarEstimate total solar system costs, apply the 30% Section 25D federal clean energy tax credit, factor utility inflation, and project your exact year of full payback.
Open calculator →Practical walkthroughs with the math shown, not just conclusions.
Evaluating the trade-offs of Level 1 trickle charging versus installing a 240V Level 2 hardwired station: panel capacity, NEMA outlets, and electrician costs.
Read the guide →How utility time-of-use rate plans work, off-peak super-saver hours, and how to program vehicle charge timers to slash electricity bills.
Read the guide →Comparing solar panel break-even payback periods across all 50 states based on electricity rates, sun hours, and net metering laws.
Read the guide →How California NEM 3.0 (Solar Billing Plan) cut solar export credits by 75%, and why adding a battery storage system restores solar investment ROI.
Read the guide →Comparing the real cost to charge an electric car at home ($0.16/kWh) versus public DC Fast Superchargers ($0.42/kWh), and the annual impact.
Read the guide →Comparing cold-climate heat pump operating costs against natural gas furnaces: COP efficiency, regional electric rates, and IRA Section 25C rebates.
Read the guide →Home and public charging cost estimates for popular EV models in every state, using EIA residential electricity rates.
Estimated solar payback periods by state with system cost, production, utility rates, and incentive assumptions.
Every calculator on WattWise is deterministic: the same inputs always produce the same output, and the formula is documented in plain language on the tool page. Where a figure depends on an external benchmark — a published rate, a statutory limit, or an industry cost range — the page cites the publisher and links to it.
We separate inputs you control (balances, rates, dimensions, weights) from assumptions we supply (default rates, waste factors, contingency percentages). Assumption defaults are deliberately conservative and every one of them is editable on the tool page, so you can substitute your own quote or local figure.
Nothing you type is transmitted. The calculations execute in JavaScript in your browser, which means the tools work offline and no personal data is collected.