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Solar Generator Sizing Calculator

Size a portable solar generator in seconds. Calculate battery Wh, inverter continuous W, and panel input W for camping, RV and outage backup loads.

Solar Generator Sizing Calculator

Daily energy (Wh)
360 Wh
Battery capacity (Wh)
444 Wh
Inverter continuous (W)
1,500 W
Solar input (W)
116 W

How to use this calculator

The solar generator calculator above turns a load profile into the three numbers every portable power station spec sheet leads with: battery capacity in Wh, inverter continuous power in W, and solar input in W. Punch in the average AC load you want to run, how many hours/day you need it, your peak surge load, and your peak sun hours — the outputs update instantly.

  1. Average load (W) — sum the running wattage of everything you intend to run at once. A laptop runs 50 W, a 12 V fridge 40–60 W, LED lights 5 W each, a CPAP 30–60 W. Phone chargers and tablets disappear into the noise.
  2. Runtime per day (h) — how many hours those loads actually run. A fridge cycles about 8 hours of 24; CPAP runs the 8 hours you sleep; laptops the 4–8 hours you work.
  3. Days of autonomy — how many cloudy days the unit needs to cover before the next sunny recharge. 1 day for fair-weather camping, 2 for shoulder seasons, 3+ for the Pacific Northwest or winter prepping.
  4. Peak surge load (W) — the largest single load you’ll start: microwave 1,200 W, hair dryer 1,500 W, refrigerator compressor start 1,500–2,200 W, table saw 1,800 W. The calculator multiplies by 1.25 to size the inverter for surge.
  5. Peak sun hours — NREL NSRDB / PVWatts averages 4.0–5.5 across the lower 48. Sun Belt: 5.0–6.0. Pacific Northwest and New England: 3.0–4.0.

How the math works

Three first-principles formulas, each derivable from energy balance:

Daily energy:

daily_Wh = avg_W × hours

At 60 W × 6 h = 360 Wh/day — typical RV / weekend load.

Battery capacity (Wh):

battery_Wh = daily_Wh × autonomy / (DoD × inverter_eff)

With 360 Wh/day × 1 day at 90% DoD and 90% inverter efficiency: 360 / 0.81 = 444 Wh. Round up to the next commercially available size — that puts you in Jackery Explorer 500 / EcoFlow River 2 Max territory.

Inverter continuous (W):

inverter_W = peak_W × 1.25

A 1,200 W microwave surge becomes a 1,500 W continuous inverter — exactly what most mid-range solar generators ship with.

Solar input (W):

solar_W = battery_Wh / (peak_sun_hours × charge_eff)

A 444 Wh battery in a 4.5 PSH region at 85% MPPT charge efficiency: 444 / 3.83 = 116 W. A 100–200 W folding panel covers it.

What a solar generator actually costs in the U.S. (Q1 2026)

Pricing pulled from Jackery, EcoFlow, Bluetti, Anker SOLIX and Goal Zero direct-to-consumer pages and EnergySage portable-power category:

Use caseBattery WhInverter WSolar input WTotal kit
Weekend camping (phone + lights + CPAP)300–500600–1,000100$400–700
RV / van life (12 V fridge + small appliances)500–1,0001,000–1,800200$700–1,500
Power outage essentials (full-size fridge + lights)1,000–2,0001,800–2,400300–400$1,500–2,800
Whole-home critical loads (fridge + HVAC blower + sump)3,000–6,0003,000–5,000600–1,200$3,000–6,500
Off-grid expandable stack (modular battery packs)6,000–18,0004,000–7,2001,200–3,600$6,500–18,000

Federal 30% Residential Clean Energy Credit (Section 25D) drops the kit price by 30% on units 3 kWh and above when installed at a primary residence. Portable use outside the home doesn’t qualify.

Where most solar generator buyers under-size

Three common mistakes from the EcoFlow, Bluetti and Jackery support forums:

  1. Sizing on running wattage, ignoring surge. A 1,000 W inverter handles a 700 W coffee maker fine but trips on a refrigerator compressor start. Always check peak surge — manufacturer spec sheets list both.
  2. One-day autonomy in cloudy climates. A 500 Wh kit with a 100 W folding panel works in Arizona. The same kit in Seattle in December gets one 2-hour charge window per day and dies on day two.
  3. Mixing chemistries. LiFePO₄ packs (Bluetti, EcoFlow Delta 2/Pro, Jackery v2) tolerate 3,000–6,000 cycles at 90% DoD. Older NMC-based units (original Jackery, Goal Zero Yeti X) cycle 500–1,000 times and don’t like deep discharges. For daily off-grid use, LiFePO₄ wins on lifetime cost-per-cycle.

Pair this with the off-grid system calculator, battery bank calculator, and RV solar calculator

This calculator gives the headline three numbers for a portable solar generator. The off-grid calculator scales the same logic to a fixed-mount cabin or homestead. The battery bank calculator drills into amp-hour capacity at your chosen system voltage if you’re building a DIY 12 V / 24 V / 48 V stack rather than buying a packaged unit. The RV solar calculator picks roof-mount panel wattage based on your tank-to-tank duty cycle.

Sources

Frequently asked questions

What size solar generator do I need for camping?
For weekend camping in the U.S. with phone chargers, a 12 V fridge, LED lights and a CPAP — about 60 W average for 6 hours/day, plus a 1,200 W microwave for short bursts — you need roughly a 500 Wh battery, a 1,500 W continuous (3,000 W surge) inverter, and a 100–200 W folding solar panel for daily recharge. Units in that range include the Jackery Explorer 500, EcoFlow River 2 Max and Bluetti EB55.
How big a solar generator do I need to run a refrigerator during a power outage?
A modern Energy Star full-size refrigerator draws about 100–150 W running and cycles roughly 8 hours/day, so 800–1,200 Wh/day. With one day of autonomy and a 90% lithium DoD that becomes a 1,000–1,500 Wh battery. Starting surge can hit 1,500–2,200 W, so you need a 2,000 W continuous inverter minimum. Realistic options: EcoFlow Delta 2, Anker 757, Bluetti AC180, Jackery Explorer 2000 v2.
What size solar panel do I need to recharge a solar generator in one day?
Take the battery Wh and divide by (peak sun hours × charge efficiency). A 1,000 Wh unit in a 4.5 PSH region (most of the lower 48) at 85% MPPT charge efficiency needs about 1,000 / (4.5 × 0.85) = 262 W of panel input. With real-world soiling and angle losses, plan on 300 W of folding panel to reliably refill the battery between sunny days.
Do solar generators qualify for the federal Investment Tax Credit?
Standalone battery storage installed at your principal residence qualifies for the 30% Residential Clean Energy Credit under IRC Section 25D if the system has a capacity of at least 3 kWh (3,000 Wh) — that includes large solar generators like the Bluetti AC500 + B300S stack and the EcoFlow Delta Pro Ultra. Smaller portable units under 3 kWh don't qualify on their own; they're treated as personal property, not a permanent residential improvement.
Solar generator vs gas generator — which makes more sense?
A 2 kWh solar generator runs the average modern fridge plus lights plus phones for about 16 hours silently with no fumes — fine for short outages. A gas generator burns 0.5–0.8 gallons/hour and outputs 5–7 kW indefinitely as long as you can get fuel — necessary for whole-home loads, well pumps, central HVAC, or multi-day outages where solar recharge is unreliable. Most U.S. preppers run both: solar for the silent first 24 hours, gas as the long-haul backup.

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