Free solar calculators. Know your numbers before you call an installer.

Free, transparent solar calculators and a source-linked incentive database for US homeowners. Production estimates use NREL PVWatts® with the assumptions shown - no email required.

Free, unlimited calculations. No account, email gate, or calculation credits required.

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Updated for 2026: the 30% federal solar tax credit for homeowners ended on Dec 31, 2025. Verify eligibility with the IRS before assuming a federal credit in a cash or loan proposal. See what changed →

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Build your solar plan in one guided flow

Enter your household basics once. We’ll carry them through system sizing, solar production, savings, financing, and incentives so you don’t keep retyping the same assumptions.

Annual usage

kWh/yr

Electric rate

$/kWh

Installed cost

$/W

Use real bill history

Import a text-based PDF, CSV, or text export with monthly kWh. Files are processed in memory and are not retained.

Start the guided plan Browse all tools Open my plan

What the workflow answers

How big your system should be
How much your roof can produce
What solar is likely to save you
Whether cash, loan, or lease looks better
Which incentives still matter in 2026

What do you want to calculate?

Start with one question. Each tool explains its inputs, a worked example and what to verify.

How many solar panels do I need?What will my electric bill be after solar?How long will a battery run my appliances?What will my solar loan payment be?What are my exported solar kWh worth?How do I compare installer quotes?

Decision workspace

One plan that keeps your numbers

Save scenarios, compare outcomes, share an address-safe link, and print a homeowner-ready report.

Open my solar plan

Proposal intelligence

Compare up to three installer quotes

Normalize total payments, price per watt, production, equipment, batteries, and warranty coverage.

Compare solar quotes

Primary-source research

Check the utility rule behind savings

Review billing models, tariff questions, source dates, and official utility verification links.

Browse utility guides

System Size Calculator

Turn your annual kWh usage into the right solar system size in kW.

Open tool →

Solar Savings Calculator

25-year savings, payback, ROI, and NPV with up-to-date 2026 tax rules.

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Incentive Finder

Search federal, state, and utility solar incentives by state.

Open tool →

Solar planning in plain English

The four numbers to check before comparing solar quotes

A useful solar estimate connects your electricity use, local sunlight, installed price, and utility export policy. Wattcrunch keeps those assumptions visible so you can change them instead of trusting a hidden sales estimate.

Annual electricity use

Use 12 months of bills in kWh. Square footage alone cannot size a solar system accurately.

Calculate system size

Local solar production

A 1 kW array produces different amounts by location, roof direction, tilt, and losses. We use NREL PVWatts for address-based estimates.

Check solar potential

Installed price per watt

Compare quotes before financing. Equipment, roof work, batteries, and dealer fees should be separated clearly.

Check a solar quote

Import and export rates

Retail electricity avoided on-site can be worth more than exported solar. Net metering and time-of-use rules materially change savings.

Model net metering

Want to audit the assumptions? Read our calculator methodology and editorial policy.

Transparent by design

See the assumptions before you trust the answer

Wattcrunch is an independent planning resource, not an installer, lender, utility, or tax adviser. We show the inputs, formulas, source hierarchy, and planning ranges so you can challenge an estimate instead of accepting a hidden sales calculation.

Production

NREL PVWatts-based location estimates with visible loss assumptions.

View primary source

Policy

Utility, government, DSIRE, and IRS references for incentive and tariff checks.

Browse utility guides

Review

Unit-tested calculators, correction guidance, and a documented update cadence.

Read the policy

Want to know who creates the content? Meet Marcus Vance, the Wattcrunch author.

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Wattcrunch is free. Help us give back.

Every calculation here is free with no account or email required. Advertising supports the site but never changes your inputs, results, or recommendations. If these tools helped you make a smarter solar decision, consider planting a tree through One Tree Planted. One dollar plants one tree, and it takes about 30 seconds.

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