How big should a home's solar array and battery be, and at what installed price does the battery pay?
research/energy-home
How big should a home's solar array and battery be, and at what price does the battery pay? Hourly model on synthetic weather (assumed inputs): a 6 kW array meets 35% of an 8,000 kWh/yr load, a 10 kWh battery lifts it to 59%, and the battery pays only below about $451/kWh installed at $0.05 export (assumed price $800).
What it found
An hourly simulation of rooftop solar plus a battery on an 8,000 kWh/yr home, over 20 seeded synthetic weather years (Haurwitz clear sky, a three-state cloud chain, an invented load) with assumed round-number prices. A 6 kW array alone meets 35% of the load; 5, 10 and 15 kWh of battery lift that to 49%, 59% and 62%, then returns diminish fast. With import at $0.30 and export at $0.05 per kWh a 10 kWh battery pays only below about $451/kWh installed (assumed $800), $143 at $0.20 export, and never when export is paid at the import price. Stylised: synthetic weather, flat tariff, no incentives or degradation; not installation advice.
A figure from its own output
Paper, code and results
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Produced with AI assistance (Claude). Results are from the code in this repository and are simulated or stylised unless the abstract says otherwise; nothing here implies affiliation with or endorsement by any lab, researcher or company cited. MIT licensed.