Solar data analysis from the National Renewable Energy Laboratory (NREL) explores the affordability of solar using a “Savings to Investment Ratio” (SIR). This metric captures the ability to recover one’s investment in solar based on the utility bill savings resulting from the solar energy generated by a given solar energy system. NREL conducted a simple SIR analysis for all 50 states by assuming that U.S. residential PV systems today cost between $3.00 per watt and $3.50 per watt and last 25 to 35 years. In this scenario, it could be cost-effective for households to make a shift to solar in a quarter to half of states without any state or local incentives.