Chapter 8 · Payback and ROI
8.1 The 7 variables that drive payback
- Local average retail rate ($/kWh)
- Annual consumption (kWh)
- Usage timing (matters under NEM 3.0)
- Solar insolation (kWh/m²/day)
- System price ($/Watt including equipment + install + battery)
- Federal + state + local incentives
- Net metering policy (the export rate)
- Utility rate inflation (~8–12% per year in California)
Next Step
Questions after reading this section? Send us your utility bill — we will come back within one business day with a recommendation specific to your situation.