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WattWise

Tools

WattWise calculators

Every tool below runs entirely in your browser. Pick a calculator, read the assumptions, and change any default that does not match your situation.

EV charging

EV charging

Electric Vehicle (EV) vs Gas Fuel Cost & Savings Calculator

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 charging

EV Charging Time & Session Cost Calculator (Level 1, 2 & DC Fast)

Enter your EV battery pack size (kWh) and starting and target charge percentages to compare charging hours and session costs across all three charging levels.

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Home solar

Home solar

Home Solar Panel ROI & Payback Period Calculator

Estimate 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.

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Our tool standards

  • No hidden inputs. Every assumption is visible and editable.
  • No data collection. Calculations run client-side; nothing is uploaded.
  • Documented formulas. Each page explains the math in plain English.
  • Cited sources. External benchmarks link to the publisher.
  • Updated dates. Pages show when they were last reviewed.
  • Accessible markup. Labeled inputs, keyboard support, and readable contrast.