Free energy calculators built on real 2026 data.
20 calculators for solar payback, system sizing, EV charging cost, and household running costs — each showing its formula, sources, and limits. Answer below in about a minute. No sign-up.
The question every solar buyer asks first. Pick your state and this loads your current electricity rate, installed cost, export policy, and any incentive still available in 2026 — then gives you the break-even year, your return, and the full 25-year cash flow.
Solar Payback Period & ROI Calculator
Find how long your solar panels take to pay for themselves, and what they return over 25 years, using May 2026 EIA electricity rates and current state incentive data.
Pick the calculation you need.
Search by what you want to work out, or browse by topic. Every tool is free, works without an account, and explains the maths behind its answer.
Showing all 20 calculators
- EV Charging Cost CalculatorCompare EV charging cost per mile at home, on public DC fast chargers, and against gasoline, using EIA electricity rates for your state.
- EV Charging Time CalculatorEstimate how long it takes to charge your electric vehicle from your battery size, charger power, and charge levels.
- EV vs Gas Savings CalculatorCompare fuel cost and total ownership savings between an electric vehicle and a gas car based on your driving and local prices.
- EV Range CalculatorEstimate how far you can drive on your current charge, in kilometres or miles, from any efficiency unit — kWh/100 km, Wh/km, km/kWh or mi/kWh.
- RV Solar CalculatorSize an RV solar setup in seconds. Get panel wattage, battery Ah, charge controller and inverter sizing using an NEC 690.8 safety margin.
- Solar Panel Estimate CalculatorEstimate your 2026 solar system size, installed cost, payback period, and 25-year savings using current EnergySage and EIA benchmarks.
- Solar Payback Period & ROI CalculatorFind out how long your solar panels take to pay for themselves, with 2026 electricity rates and incentive data for all 50 states plus ROI, IRR, and year-by-year cash flow.
- Solar Panel CO₂ Savings CalculatorEstimate the annual and 25-year CO2 emissions avoided by your PV system, using EPA eGRID 2024 grid emission factors.
- Solar Fuse Size CalculatorSize DC fuses for any PV string, battery bank, or inverter, using Isc and continuous-current NEC 690.9 rules.
- How Many Solar Panels Do I Need?Find how many solar panels you need from your monthly kWh, sun hours, and panel wattage, with roof area and production estimates.
- Solar Pool Pump CalculatorSize a solar-powered pool pump and array. Get required flow, pump wattage, panel size, and dollar savings versus your existing pool pump.
- Solar Loan CalculatorEstimate your monthly solar loan payment, total interest, and net monthly cost — search your country, price it in 95 currencies, on flat or reducing-balance rates.
- Solar Panel Snow Load CalculatorCompute flat- and sloped-roof snow loads with per-anchor shear demand, built on ASCE 7 ground snow values.
- Hybrid Solar System CalculatorSize a grid-tied hybrid solar system: PV array kW, battery kWh, hybrid inverter capacity, and annual self-consumption.
- Solar Tax Credit CalculatorWork out your federal Section 25D residential solar tax credit, your state credit, and how much you can actually claim this year.
- Solar Investment Tax Credit CalculatorEstimate your Section 48E ITC, MACRS depreciation tax shield, and net cost for a U.S. commercial or business solar project.
- Solar Feed-in Tariff Calculator (U.S. Net Metering)Estimate your annual solar export revenue and self-consumption savings, covering NEM 1.0 retail credit and NEM 3.0-style avoided-cost export rates.
- Mortgage CalculatorEstimate your full monthly mortgage payment including PMI, property tax, insurance and HOA, plus total interest and payoff date.
- Refinance CalculatorCompare your current mortgage against a new one to find your monthly saving, break-even point, and whether refinancing costs you more interest overall.
Every figure has a source you can check.
Electricity rates come from the EIA's Electric Power Monthly (May 2026). Incentives are checked against DSIRE. Both are reviewed at least annually — last pass August 2026.
Each calculator states the equation it uses and works through a full example, so you can verify the answer by hand instead of trusting a black box.
Where a model simplifies — flat rates instead of time-of-use, no financing interest — we say so on the page rather than burying it.
Every calculation runs client-side. No inputs are sent to a server, and no account is needed to use any tool.