Guided Workflow

Step 1 of 9. Follow the sequence to turn a rough idea into a homeowner-ready solar plan.

Solar Calculators

17 free tools - from system sizing to TOU optimization, EV charging, backup loads, quote checking, and shading analysis. Each tool shows its assumptions so you can review the inputs behind the estimate.

Start Here

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

Choose the solar question you need to answer

Costs, quotes and payback

Compare installed cash price per watt before financing. Keep batteries, roof work and dealer fees separate, then test output and export assumptions.

Compare solar installation quotes

Estimate payback and ROI · Quote comparison checklist

Panels, production and bill offset

Start from 12 months of kWh, not house area alone. Panel wattage determines panel count; your roof and local production determine annual output.

Calculate panels from electricity usage

Model the bill after solar · Check utility settlement rules

Battery storage and backup duration

Size essential loads in kWh, then check inverter kW and surge capacity. Backup resilience and electricity-bill savings are different benefits.

Estimate essential-load backup duration

Size battery capacity and power · Battery sizing guide

Financing, EV charging and future demand

Compare total financed cost, not just payment. Add future vehicle charging and heating demand before choosing system size.

Calculate a solar loan payment

Compare cash, loan, lease and PPA · Size solar for EV charging

Core Tools

The fundamentals - every homeowner should run these before signing anything.

kW to kWh Calculator

Convert power and hours into energy, Wh and megajoules with instant results.

Open →

System Size Calculator

kWh usage → kW system, panel count, roof area.

Open →

Solar Savings Calculator

25-year savings, payback, ROI, NPV.

Open →

Solar Potential (by address)

Address → NREL PVWatts production estimate.

Open →

Payback / ROI Calculator

Break-even year and return on investment.

Open →

Net-Metering Estimator

Self-used vs exported energy at full retail or net-billing rate.

Open →

Bill Savings Estimator

Your new monthly bill after solar.

Open →

Solar Loan Calculator

Monthly payment, total interest and historical credit eligibility.

Open →

Lease vs Buy vs PPA

Compare all four ownership paths over 25 years.

Open →

Battery Storage Sizing

kWh of backup needed from your loads.

Open →

Specialized Tools

Explore storage, electrification and equipment assumptions.

New

TOU Rate Optimizer

Model solar + battery under time-of-use electricity rates. See peak arbitrage value.

Open →New

Solar + EV Calculator

Estimate extra solar capacity for EV home charging.

Open →New

Backup Load Sizer

Select appliances to estimate kWh needs and battery runtime.

Open →New

Quote Comparison

Compare cash-equivalent price, financing, equipment and disclosures.

Open →New

Shading Loss Estimator

How much do trees or chimneys cut output - and is a microinverter worth it?

Open →New

Solar + Heat Pump

How much extra solar to cover a heat pump replacing gas or oil heat.

Open →New

Carbon Impact Calculator

CO₂ offset, trees equivalent, car miles avoided over 25 years.

Open →

⚠ 2026 accuracy note

The federal residential solar tax credit (Section 25D) expired December 31, 2025 under Public Law 119-21. All Wattcrunch calculators reflect this - homeowner-owned systems placed in service after December 31, 2025 receive $0 federal credit. Review the IRS guidance and confirm tax treatment with a qualified professional.

Embed Wattcrunch on Your Site

Writing about solar? Give your readers an interactive calculator without leaving your page. Wattcrunch calculators are free to embed - no API key, no sign-up required.

System Size Calculator

kWh usage → kW system size, panel count, roof area.

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  src="https://wattcrunch.tech/calculators/system-size"
  width="100%"
  height="640"
  frameborder="0"
  loading="lazy"
  title="Wattcrunch Solar Calculator"
></iframe>

Preview this calculator →

Solar Savings Calculator

25-year savings, payback period, ROI, NPV.

<iframe
  src="https://wattcrunch.tech/calculators/solar-savings"
  width="100%"
  height="640"
  frameborder="0"
  loading="lazy"
  title="Wattcrunch Solar Calculator"
></iframe>

Preview this calculator →

Solar Payback Calculator

Break-even year and lifetime return on investment.

<iframe
  src="https://wattcrunch.tech/calculators/payback"
  width="100%"
  height="640"
  frameborder="0"
  loading="lazy"
  title="Wattcrunch Solar Calculator"
></iframe>

Preview this calculator →

Quote Fairness Checker

Compare solar-only cash price, financing fees and warranty disclosures.

<iframe
  src="https://wattcrunch.tech/calculators/quote-checker"
  width="100%"
  height="640"
  frameborder="0"
  loading="lazy"
  title="Wattcrunch Solar Calculator"
></iframe>

Preview this calculator →

Attribution link to wattcrunch.tech is included automatically. For custom sizing or a different calculator, contact us.