Solar Generator Size Guide: How Many Watt-Hours Do You Actually Need?
The most common solar generator mistake is buying the wrong size — usually too small because the buyer focused on price, or too large because a comparison chart scared them into overspending. Both errors are avoidable with one hour of upfront math.
Solar generator capacity is measured in watt-hours (Wh)— the product of power (watts) and time (hours). A 100W bulb running for 10 hours consumes 1,000 Wh (1 kWh). Your solar generator's Wh rating is the tank size; your appliances' consumption rate is how fast you drain it. Get those two numbers right and everything else follows logically.
There is a second number that buyers routinely underestimate: inverter output watts — the maximum power the unit can deliver simultaneously. A solar generator with 2,000 Wh of capacity but only a 1,000W inverter cannot start a standard refrigerator, regardless of how much energy is stored. Capacity and output are independent specs, and both must match your load.
This guide provides a complete sizing framework — use the calculator below to generate your personalized watt-hour requirement, then use the tier breakdown and use-case tables to find the right capacity class.
Select the appliances you plan to power below. The calculator shows your total running watts, startup surge, and daily watt-hour requirement — the three numbers that determine your ideal solar generator size.
Portable Generator Size Calculator
Select the appliances you need to power — we'll calculate the right portable generator size instantly.
Select appliances to calculate load
Opens Amazon search · Affiliate link
The 3 Numbers That Determine Solar Generator Size
Every solar generator purchase decision comes down to matching three numbers. Miss any one and either the unit shuts down under load or runs out of energy before you expect it to.
Solar Generator Sizing Framework
Running Watts → Minimum Inverter Output
Sum all appliances running at the same time
Why it matters: The inverter continuous output rating must exceed this number. Exceeding it trips the overload protection.
Example: Fridge 150W + window AC 900W + TV 100W + lights 80W = 1,230W → need 1,500W+ inverter
Startup Surge Watts → Minimum Inverter Surge Rating
Largest motor appliance × 2–3× surge multiplier
Why it matters: Compressor motors (AC, fridge, sump pump) spike 2–3× rated watts for 200–500 ms at startup. The inverter surge rating must cover this peak.
Example: Window AC rated 900W × 2.5 surge = 2,250W → need inverter with 2,500W+ surge capacity
Daily Watt-Hours → Minimum Battery Capacity
(Each appliance W × daily hours) summed × 1.4 buffer
Why it matters: The 1.4 multiplier accounts for 85% inverter efficiency and 80% usable depth-of-discharge (never drain an LFP battery to zero — it shortens lifespan).
Example: Fridge 150W×8h=1,200Wh + Starlink 65W×8h=520Wh + lights 50W×6h=300Wh = 2,020Wh raw × 1.4 = 2,828Wh → 3,000Wh unit
Key Insight: Capacity and Output Are Independent
A 2,000 Wh battery with a 1,000W inverter cannot start a refrigerator — not because it lacks stored energy, but because the inverter trips on the startup surge. Conversely, a 500W inverter with 5,000 Wh stored energy is useless for high-power appliances. Always confirm both numbers for your specific load.
Solar Generator Capacity Tiers: What Each Size Can Actually Do
The market segments naturally into five capacity tiers. Each tier represents a genuine capability jump — it is not just a larger battery, but a different category of use case.
500 – 999 Wh
Typical weight
10–18 lbs
Best for: Weekend camping, day hikes, emergency phone charging
Can Run
- Phone + laptop charging (3–5 cycles each)
- LED lights all night (~30Wh)
- CPAP without humidifier — 1 night
- Mini fridge for 3–5 hours
Cannot Run
- Window air conditioner
- Full-size refrigerator overnight
- Starlink for more than 8–10 hours
- Electric griddle or coffee maker long-term
1,000 – 1,499 Wh
Typical weight
22–32 lbs
Best for: Car camping 2–3 days, van weekend trips, small emergency backup
Can Run
- CPAP machine all night (2 nights without humidifier)
- Starlink for 14–16 hours
- Laptop + phone charging for 3 days
- Portable 12V fridge for 10–14 hours
Cannot Run
- Window air conditioner (insufficient inverter output)
- Full-size fridge more than 5–6 hours
- Electric kettle or griddle repeatedly
1,500 – 2,499 Wh
Typical weight
38–55 lbs
Best for: Multi-day off-grid camping, RV electronics, 1–2 day home backup
Can Run
- Full-size refrigerator for 8–12 hours
- Home essentials (fridge + lights + Wi-Fi) for 1.5–2 days
- Small window AC for 2–3 hours
- Starlink indefinitely with 200W+ solar panel
Cannot Run
- Central air conditioner
- Electric water heater
- Multi-day AC use without solar recharging
2,500 – 3,600 Wh
Typical weight
65–99 lbs
Best for: Multi-day home backup, 30-amp RV air conditioning, full-time van life
Can Run
- Full-size fridge for 20–24 hours
- Window AC (5,000 BTU) for 5–7 hours
- Home essentials for 3–5 days
- 30-amp RV air conditioner (requires 3,600W inverter)
Cannot Run
- Central HVAC system
- 50-amp RV full load simultaneously
- Electric range / oven
3,600+ Wh (Expandable)
Typical weight
99+ lbs (base unit)
Best for: Extended outages, whole-home backup, semi-permanent off-grid installation
Can Run
- Most whole-home appliances simultaneously
- Dual RV air conditioners
- Electric well pump (with sufficient surge rating)
- Home office with power tools
Cannot Run
- Electric dryer (5,000–7,000W) without fuel generator
- Central electric furnace (10,000–15,000W)
Right-Size by Use Case
Camping: Quick-Reference Size Chart
| Camping Setup | Daily Usage | Minimum Size |
|---|---|---|
| Phone + lights + fan | ~200 Wh/day | 500 Wh |
| Above + laptop | ~350 Wh/day | 700 Wh |
| Above + Starlink | ~900 Wh/day | 1,000 Wh |
| Above + CPAP (no humidifier) | ~1,200 Wh/day | 1,500 Wh |
| Above + portable 12V fridge | ~1,600 Wh/day | 2,000 Wh |
| Above + small electric griddle | ~2,200 Wh/day | 2,500 Wh |
* Minimum sizes assume daily solar recharging with a 200W panel (5+ peak sun hours). Without solar, double the capacity for multi-day trips.
Home Backup: Hours of Runtime by Appliance Load
| Scenario | Load | 1,000 Wh | 2,000 Wh | 3,600 Wh |
|---|---|---|---|---|
| Fridge only | ~150W | 5–6 hrs | 11–12 hrs | 20–22 hrs |
| Essentials (fridge + lights + Wi-Fi) | ~350W | 2.5 hrs | 5 hrs | 9–10 hrs |
| Essentials + window AC (5k BTU) | ~850W | ~1 hr | ~2 hrs | ~4 hrs |
| Home office (PC + monitor + router) | ~300W | 3 hrs | 6 hrs | 11 hrs |
| Medical devices (CPAP + O2 concentrator) | ~350W | 2.5 hrs | 5 hrs | 9 hrs |
* Assumes 85% inverter efficiency and 90% usable capacity. Actual runtime varies with battery temperature and age.
RV & Van Life: Sizing by Amp Service
30-Amp RV (Electronics Only)
- Microwave, TV, device charging, lighting
- Running draw: 500–800W
- Daily use: 1,500–2,500 Wh
- Recommended size: 2,000–2,500 Wh, 2,200W+ inverter
30-Amp RV with Air Conditioner
- 13,500 BTU AC + essentials
- Startup surge: up to 3,500W
- Daily use: 5,000–8,000 Wh
- Recommended size: 3,600 Wh, 3,600W+ inverter (DELTA Pro min.)
50-Amp RV / Class A (Dual AC)
- Dual 15,000 BTU ACs + residential fridge
- Running draw: 3,500–5,000W
- Daily use: 12,000–20,000 Wh
- Recommended: Paired DELTA Pro units + solar array
Van Life / Stealth Camping
- 12V fridge, laptop, Starlink, lighting
- Running draw: 150–300W
- Daily use: 1,000–2,000 Wh
- Recommended size: 1,500–2,000 Wh + rooftop 200W panel
How to Size Solar Panels for Your Solar Generator
Once you know your daily watt-hour requirement, sizing the solar panel array is straightforward arithmetic. The key variable is peak sun hours — the number of hours per day when solar irradiance averages 1,000 W/m². This is not daylight hours. In most of the continental US, peak sun hours range from 3.5–6 hours/day depending on latitude and season.
Solar Panel Size Formula
Panel Watts needed = (Daily Wh ÷ Peak Sun Hours) × 1.25
The 1.25 factor accounts for panel efficiency losses (temperature, angle, wiring)
Weekend camping (1,000 Wh/day, 5 sun hrs)
1,000 ÷ 5 × 1.25 = 250W of panels
2× 100W foldable panels or 1× 200W rigid panel
Van life (2,000 Wh/day, 5 sun hrs)
2,000 ÷ 5 × 1.25 = 500W of panels
2× 200W rigid rooftop panels or 3× 160W flexible panels
Home backup essentials (3,500 Wh/day, 4 sun hrs)
3,500 ÷ 4 × 1.25 = 1,094W of panels
3–4× 300W ground-mount or roof panels + 800W max MPPT input
Check Your Unit’s Max Solar Input
Every solar generator has a maximum MPPT solar input rating (e.g., 600W, 800W, 1,600W). Connecting more panel wattage than this limit provides zero additional charging speed and may trigger protection circuits. Match your panel array to the unit's input ceiling.
| Unit | Capacity | Max Solar Input | Solar Recharge Time (400W panel) |
|---|---|---|---|
| Jackery Explorer 1000 Pro | 1,002 Wh | 200W | ~6 hrs |
| EcoFlow DELTA 2 | 1,024 Wh | 500W | ~2.5 hrs |
| Bluetti AC200MAX | 2,048 Wh | 900W | ~3 hrs |
| Jackery Explorer 2000 Pro | 2,160 Wh | 1,400W | ~2.5 hrs |
| EcoFlow DELTA Pro | 3,600 Wh | 1,600W | ~2.8 hrs |
Solar Generator Size FAQ
What size solar generator do I need?
The correct size depends on three numbers: (1) your peak running watts — the sum of all appliances running at once, which determines the minimum inverter output; (2) your highest motor's startup surge, which is 2–3x its rated watts; and (3) your daily energy in watt-hours — each appliance's wattage multiplied by hours of daily use, summed, then multiplied by 1.4 for efficiency losses. The calculator above computes all three automatically. For basic camping, 1,000 Wh is typical. For home essentials backup, 2,000–3,600 Wh. For full-home backup with AC, 3,600+ Wh with solar recharging.
Is a 1000Wh solar generator enough for camping?
Yes, for most weekend car campers. A 1,000 Wh solar generator covers: a CPAP machine for 2 nights without humidifier (320–480 Wh), Starlink for 14–16 hours (500–700 Wh), laptop charging 8–10 times (300–500 Wh), LED lighting and phone charging for 3 days (150–250 Wh). The constraint is that you cannot run all of these simultaneously — a 1,000 Wh unit used for Starlink plus CPAP nightly will be near-empty by day 3 without solar recharging. Pair it with a 200W panel for indefinite off-grid operation.
Is 2000Wh enough for home backup?
For essential loads only — yes. A 2,000 Wh solar generator running a refrigerator (150W × 24h = 3,600 Wh/day) alone exceeds the capacity overnight, so you need to run the fridge intermittently or supplement with solar. Realistic essential-load budgets: refrigerator 2 hours on / 1 hour off (800 Wh), LED lighting (200 Wh), phone/laptop charging (150 Wh), Wi-Fi router (100 Wh) — roughly 1,250 Wh/day for a disciplined household. A 2,000 Wh unit lasts 1.5–2 days before needing recharge. For air conditioning, step up to 3,600 Wh minimum.
How many watts does a solar generator need to run a refrigerator?
A full-size refrigerator draws 100–200W running, but requires a 600–1,200W startup surge due to the compressor motor. Your solar generator's inverter must handle the surge — a 1,000W inverter will trip on startup even if the running draw is only 150W. Use a solar generator with at least a 1,500W continuous inverter and 2,000W surge capacity. Recommended minimum capacity: 1,500 Wh for overnight-only operation, 3,000+ Wh for full 24-hour fridge power.
How do I calculate how many solar panels I need to recharge a solar generator?
Formula: daily energy use (Wh) divided by local peak sun hours (typically 4–6 hours/day in the US), then add 25% for panel inefficiency. Example: 2,000 Wh/day used, 5 peak sun hours available: 2,000 ÷ 5 = 400W of panels, × 1.25 = 500W total panel capacity needed. Also check your solar generator's maximum solar input rating — connecting more panel wattage than the unit's MPPT controller accepts provides no benefit and may damage the unit.
What is the largest portable solar generator available in 2026?
The EcoFlow DELTA Pro Ultra is the highest-capacity standalone portable solar generator at 6,144 Wh base, expandable to 21.6 kWh with add-on batteries. It outputs 7,200W of AC power — enough to run central air conditioning and most whole-home loads. For most residential use cases, the standard EcoFlow DELTA Pro (3,600 Wh, 3,600W output, expandable to 25 kWh) is the practical maximum before crossing into stationary home battery territory.
What solar generator size is right for an RV?
For a 30-amp RV running a 13,500 BTU air conditioner: you need a 3,600W+ inverter and 3,600+ Wh capacity — the EcoFlow DELTA Pro is the minimum viable unit. For electronics-only RV use (no AC): a 2,000 Wh unit with 2,200W output covers a microwave, fridge, TV, and device charging. For full-time RV living with rooftop solar: pair a 2,000–3,600 Wh unit with 400–800W of panels for self-sufficient daily operation.
Related Guides
Best Portable Generator for Camping
Gas inverter vs. solar power station — noise rules, wattage, and top picks.
RV Generator Size Calculator
30-amp and 50-amp RV power requirements with AC load breakdowns.
Home Backup Generator Sizing
How to calculate essential vs. whole-home circuit requirements.
Solar vs. Gas Generator
Full cost, runtime, and use-case comparison between fuel types.