Is it cheaper to run a generator or solar?

For daily use, solar wins economically after 5-10 years. A 7.5kW generator running 8 hours/day at $3.50/gal costs $7,000-$8,000/year in fuel alone. An equivalent solar+battery system costs $20,000-$40,000 installed but then runs nearly free for 25+ years.

Generator to Solar Calculator

Compare generator running costs vs solar + battery. See the equivalent solar system size, 10-year cost comparison, and your payback period.

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Generator vs solar comparison

Payback in 5.2 years

Generator annual cost$4,073/yr

— Fuel cost$3,679/yr

— Maintenance est.$394/yr

Equivalent solar system8.4 kW (21 panels)

Battery storage needed45 kWh

Solar system cost$21,000

10-year savings$18,894

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How to Use This Calculator

Enter your generator's power rating (kW), fuel cost per gallon, and daily running hours. The calculator compares the total 10-year cost of generator operation against an equivalent solar + battery system, and estimates your payback period.

What counts as an "equivalent" solar system

The solar system is sized to produce the same daily energy as the generator runs during your specified hours. Battery storage is sized for one night of operation. This gives a fair comparison — solar + battery replaces the generator for daily use, not just occasional backup.

When solar beats a generator

Solar wins over 10 years when: fuel costs are high ($3+/gallon), the generator runs daily, and generator maintenance costs are factored in (oil changes, spark plugs, carburetor cleaning, eventual engine replacement). Most generators run for 1,000-2,000 hours before needing major service — a daily-use generator may need engine work every 1-3 years.

True Cost of Generator Operation

Annual fuel cost = generator kW × run hours/day × fuel consumption rate × $/gal × 365 Fuel consumption: gasoline ~0.5 gal/kWh, propane ~0.67 gal/kWh Annual maintenance: $200-500/yr (oil, filters, service) 10-year generator cost = fuel cost × 10 + maintenance × 10 + 1-2 engine rebuilds ($500-1,500)

For a 7.5kW generator running 8 hours/day at $3.50/gal gasoline: fuel alone costs ~$7,700/year ($77,000 over 10 years). A solar + battery system with similar output costs $15,000-$30,000 installed and then runs nearly free for 25+ years.

FAQ

How big a solar system do I need to replace a generator? ▼

To replace a generator used for daily power, size the solar array to produce the same daily kWh as the generator. A 7.5kW generator running 8 hours/day produces 60 kWh/day — that requires a ~15kW solar array plus 20-30 kWh of battery storage. This is a large investment ($40,000-$60,000) but replaces thousands of dollars in annual fuel costs. For occasional backup use (hurricane season), a 5-10 kWh battery with 2-4kW solar is often sufficient.

Is it worth replacing a generator with solar? ▼

For generators that run regularly (daily or multiple times per week), solar + battery almost always wins economically after 5-10 years. For generators used only a few times per year for emergency backup, the economics are less clear — the generator has lower upfront cost, and with minimal use, fuel costs don't accumulate. The non-economic factors favor solar: no fuel storage, no noise, no fumes, no maintenance, and instant-on operation.

Can I use solar and a generator together? ▼

Yes — a hybrid system is often the most practical approach. Solar handles daily power generation, batteries provide overnight and cloudy-day storage, and a small generator provides backup during extended bad weather. Many hybrid inverters (Victron Quattro, SMA Sunny Island, Schneider XW+) are designed to manage all three sources automatically. The generator runs far less frequently, dramatically reducing fuel and maintenance costs while maintaining full reliability.

Generator to Solar Calculator

How to Use This Calculator

What counts as an "equivalent" solar system

When solar beats a generator

True Cost of Generator Operation

FAQ

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