What Size Solar Generator Do You Need? Match the Job

Key Takeaways

• Two specs answer everything: watt-hours = how long, watts = how big — the portable version of the kW/kWh distinction.
• Size to the job, not the aisle: devices-weekend ≈ 250–500 Wh; camp kitchen ≈ 1,000 Wh; fridge-through-outage ≈ 2,000+ Wh with real output headroom.
• Surge matters: compressors and pumps demand brief multiples of their running watts — the spec that separates "runs my fridge" from "error light."
• Whole-house is not on this menu — that's wall-battery or EV territory; portables end at essentials.

The two-number method

Every solar generator decision reduces to the tank-and-tap arithmetic: sum your loads' watt-hours per day (watts × hours each), and identify the largest simultaneous wattage including surge. The first number sizes capacity, the second screens output rating — and a unit failing either is the wrong unit regardless of price or brand gloss.

Worked example, the classic outage fridge: running draw perhaps 150 W but ~1–1.5 kWh per day of energy, with compressor starts surging past 700 W. The spec sheet you need: 2,000 Wh-class capacity (a day-plus of fridge), 1,000+ W output with surge headroom, and solar input to extend indefinitely — panels feeding it by day while it hums.

The job-based tiers

Capacity classes per prevailing market tiers; the loads spreadsheet is yours to fill.

The top row's honesty check cuts both ways: past ~3,000 Wh with expansion batteries, portable pricing collides with installed wall-battery economics — at which point wheels and handles are what you're paying for, and the three-job test should referee.

The specs under the headline

Surge rating — motors (fridges, pumps, saws) briefly demand multiples of running watts; units list surge separately, and it's the number that decides compressor loads. Solar input ceiling — a big tank with a straw-sized input recharges glacially; match panel wattage plans to the input spec. Chemistry — LFP cells dominate current models for the same cycle-life reasons they won wall storage; older NMC stock discounts accordingly. Expansion ports — buying the middle tier with expansion beats overbuying capacity you haven't measured a need for, the same start-small logic storage sizing teaches at house scale.

Size the job, screen the surge, and the aisle full of lookalike boxes collapses to the two or three that actually fit — which was always the point of doing arithmetic before shopping.