Free Interactive Tool
Solar Generator Size Calculator: What Size Do You Actually Need?
Pick the appliances and devices you want to power, tell us roughly how many hours a day you use them, and this tool calculates the battery capacity (Wh), inverter size (W), and solar panel wattage you need — then matches you with portable power stations from our 2026 guides.
1. What do you want to power?
0 devices selectedAdjust hours per day to match your real usage. Refrigerators and freezers use a typical 8-hour daily duty cycle.
2. Your sizing recommendation
Estimates assume LiFePO4 chemistry (≈90% usable capacity) and update live as you change the inputs.
1 day = size for overnight/outage; 3 days = longer emergency runs.
US average ≈ 4–5 hrs. Desert states ≈ 6; northern/winter ≈ 3.
Best matches from our 2026 guides
Select appliances above to see matching units.
These are planning estimates only. Actual draw varies by model, age, and conditions — always check your appliance nameplate (volts × amps) and the manufacturer spec sheet before buying. See our full sizing guide for the step-by-step method.
How This Calculator Works
The tool uses the same four-step sizing method professional buyers use, adapted for portable power stations:
1. Daily energy demand (watt-hours)
For each device: typical running watts × hours used per day. Refrigerators and freezers cycle on and off, so we use the commonly cited 8-hour daily duty cycle (about one-third of a 24-hour day) — the same assumption used by Energy.gov and retail energy calculators. Sum everything to get your Wh/day.
2. Battery capacity (watt-hours)
Daily Wh × days of autonomy ÷ 0.9. Modern solar generators use LiFePO4 cells that can be safely discharged to roughly 10% remaining capacity, so we assume about 90% usable energy. We round up to the nearest 100 Wh and recommend you buy at least that capacity — a little more gives you headroom on cloudy days.
3. Inverter size (watts)
We sum the running watts of everything you might run at once, add 20% headroom, and round up to a standard size. We also add your single largest surge wattage (from motors like fridges, pumps, and AC compressors) to estimate peak demand — most stations support roughly 2× their rated output for a few seconds, but continuous output is what matters most.
4. Solar panel wattage
Daily Wh ÷ peak sun hours × 1.3. The 1.3 factor accounts for real-world losses (panel angle, heat, charge-controller efficiency, wiring). We default to 4.5 peak sun hours, the US average, and report how many 200W panels that means. If you mostly charge from wall power, you can safely ignore this number.
Product matches are filtered from our database of 2026 portable power stations by comparing the recommended battery capacity and continuous AC output against each unit’s published specifications (capacity Wh, AC output W, surge W) from the manufacturer’s product page. We sort by the smallest adequate unit first — the best value for your needs — and always show current pricing from Amazon.
Appliance Wattage Reference Table
Typical ranges based on U.S. Department of Energy data, manufacturer spec sheets, and generator-industry wattage guides. The calculator uses the midpoint of each range as its default running wattage.
| Appliance | Running watts | Surge watts | Typical hrs/day |
|---|
Surge watts apply mainly to motorized appliances (compressors, pumps, fans) during the first few seconds of startup. Values are typical ranges — your exact model may differ.
Sources & Data Verification
We compiled the wattage figures above by cross-referencing multiple independent sources, then used the consistent midpoints. Product specifications come from each manufacturer’s official product page. We do not physically test units; our methodology is transparent data synthesis. Learn more on our Editorial Standards page.
- • U.S. Department of Energy, Energy Saver — Estimating Appliance and Home Electronic Energy Use
- • U.S. DOE Energy Saver Appliance Energy Calculator (archived copy via Wayback Machine)
- • Champion Power Equipment — Generator Selector wattage guide
- • Michael Bluejay — How much electricity do household items use?
- • ElectricityPlans.com — Refrigerator wattage analysis
- • ResMed AirSense 10 specification sheet (CPAP power draw reference)
- • Manufacturer product pages — EcoFlow, Jackery, Anker, Bluetti, Pecron, OUPES
Solar Generator Sizing FAQs
Quick answers to the sizing questions we get most.