When choosing backup power, the two main options are a generator (gasoline, propane, or natural gas) and a solar + battery system. They serve the same core purpose — keeping the lights on during outages — but work very differently in cost, convenience, and long-term economics.
Generator: Lower Upfront, Higher Operating Cost
A portable gasoline generator (5–10kW) costs $500–2,000. A standby generator (whole-home, natural gas/propane) costs $5,000–15,000 installed. Running cost: a 5kW generator on gasoline burns about 0.75 gallons/hour, costing $2.25–3.00/hour at current prices. For a 72-hour outage powering essential loads, fuel cost runs $100–200. Maintenance includes annual service, oil changes, and fuel stabilizer. Generators are noisy (65–75 dB) and require outdoor ventilation.
Solar + Battery: Higher Upfront, Near-Zero Operating Cost
A solar system with battery backup (e.g., 6kW solar + 1 Powerwall) costs $25,000–35,000 installed. Operating cost during outages: essentially zero — the battery charges from the panels during the day. A 13.5 kWh Powerwall covers essential loads (refrigerator, lights, phone charging, some outlets) for 12–24 hours. In multi-day outages with sun, the system recharges daily. No fuel, no noise, no fumes. The system also generates electricity savings every day — not just during outages.
Which Makes More Sense?
- Short, infrequent outages (under 24 hours): A $500–2,000 portable generator is hard to beat on pure economics
- Frequent or multi-day outages: Solar + battery becomes more attractive — fuel costs add up, and daily solar savings improve the overall ROI
- Whole-home backup for critical loads: A standby generator ($10,000–15,000) vs. larger battery system ($25,000+) — generator wins on cost if fuel is available
- Long-term, everyday value: Solar + battery wins — it generates savings 365 days/year, not just during outages