What size solar generator do I need?
Check your appliances below. You'll get the exact running watts, the startup surge that actually decides which station works, and the battery size for a full day of runtime — plus up to three matches. Numbers first, marketing nowhere.
Quick start — pick your situation:
🏠 My house🚐 RV / camper⛺ Camping🧊 Fridge only💧 Well pump🛠️ Power tools1. Check what you need to power
Refrigeration & Freezers
Kitchen
Heating, Cooling & Fans
Water & Pumps
Laundry & Cleaning
Electronics & Office
Medical Devices
Power Tools & Outdoor
Lighting
2. Your sizing
Pick appliances on the left — results update instantly.
How this calculator works
Pick what you need to power and set quantities. Every wattage is sourced from the U.S. DOE Energy Saver database, ENERGY STAR certified-product data, or manufacturer spec sheets — with typical model ranges shown where they vary.
Running load is the sum of all devices. The critical number is the startup surge: fridge compressors, well pumps and A/C units draw 2–5× their running power for a split second (locked-rotor amps). Undersize this and your station trips.
Your surge and daily watt-hours are matched against published specs of current EcoFlow, Jackery, Bluetti, Anker SOLIX, Goal Zero and Generac stations — ranked by fit, with estimated days of runtime per model.
Quick answers to common questions
| Situation | Running | Startup peak | Battery needed |
|---|---|---|---|
| what size generator to run a refrigerator | 125 W | 1,200 W | 1,250 Wh |
| what size generator do I need for home backup | 2,369 W | 4,569 W | 3,270 Wh |
| what size generator do I need for a 30 amp rv | 3,069 W | 9,069 W | 19,330 Wh |
| what size generator for cpap machine | 75 W | 92 W | 700 Wh |
| what size generator to run a well pump | 1,150 W | 7,400 W | 720 Wh |
| what size generator do I need for camping | 228 W | 428 W | 1,790 Wh |
FAQ
How do I calculate what size generator I need?
Add up the running watts of everything you want to power, then find the single device with the highest startup surge (fridge compressors, well pumps and AC units draw 2-5× their running power for a split second). Your generator must cover the surge, and its battery (Wh) must cover a day of use. The calculator above does both for you from DOE, ENERGY STAR, manufacturer specs and cross-checked industry tables.
Watts vs watt-hours — which one decides "size"?
Watts (and the startup surge) decide which devices you can RUN — that is the inverter rating. Watt-hours decide how LONG you can run them — that is battery capacity. A 2,000W / 2,000Wh station and a 2,000W / 300Wh station run the same things for very different amounts of time.
Is WattSizer biased toward any brand?
No. Recommendations match your calculated surge and daily energy against published specs from EcoFlow, Jackery, Bluetti, Anker SOLIX, Goal Zero and Generac, ranked by fit — brands do not buy placement. We may earn a commission when you buy through links on this site.