calc.engineer / Solar & Power / Solar ROI

Solar ROI v1.0.0

Calculates solar system return on investment, payback period, and levelized cost of energy (LCOE). Models year-by-year savings accounting for panel degradation, utility rate inflation, federal Investment Tax Credit (ITC), state rebates, and annual maintenance. Outputs net cost after incentives, payback year, total lifetime savings, ROI percentage, and LCOE in cents/kWh. Essential for residential and commercial solar financial analysis, installer proposals, and comparing solar vs. grid economics over a 25-year system lifetime.

← from solar_sizing.total_panel_watts
Total installed system cost in USD
System size in kilowatts (kW)
Estimated annual energy production in kWh (from PVWatts or system_size_kw * peak_sun_hours * 365 * 0.80)
Current electricity rate in cents per kWh, default 15
Annual utility rate increase percentage, default 3%
Federal Investment Tax Credit percentage, default 30% (US ITC)
State or local rebate amount in USD, default 0
Annual panel degradation rate, default 0.5% per year
Annual maintenance cost in USD, default $100
System lifetime in years, default 25
Fill in the inputs and Compute to see the structured result.

From an agent (MCP) or the API

curl -X POST https://calc.engineer/api/solar_roi \
  -H "Content-Type: application/json" \
  -d '{"system_cost_usd": …, "system_size_kw": …, "annual_production_kwh": …}'

MCP: connect to https://calc.engineer/mcp and call solar_roi.

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