Last reviewed: May 14, 2026 · Reviewed by Mike Torres, Electrical Specialist
Sizing a solar generator is one calculation: device wattage times hours of use equals watt-hours needed. Add 25% buffer for inverter losses and unexpected draw. That total is the minimum capacity for one day of use. For multi-day backup, multiply by the number of days or pair with solar panels for daily recharge. Below is the formula in plain math, a common appliance wattage chart, and three real-world scenarios for camping, 24-hour home backup, and 3-day outages.
Device Watts × Hours of Use = Watt-Hours Needed
Then multiply total by 1.25 for inverter losses
Example calculation for a typical weekend camp:
Total: 1,200Wh per day. Times 1.25 (inverter loss buffer) = 1,500Wh minimum capacity. A 1,500Wh+ unit covers one day. For a 3-day trip, either size up to 4,500Wh or pair a 1,500Wh unit with a 200W solar panel for daily recharge.
| Device | Wattage | Note |
|---|---|---|
| Refrigerator (full-size) | 100-200W avg | cycles on/off |
| Mini fridge | 40-60W avg | cycles on/off |
| Chest freezer (small) | 80-100W avg | cycles on/off |
| 12V camping fridge | 30-50W avg | low-draw |
| CPAP (no humidifier) | 30-60W | continuous overnight |
| CPAP (with humidifier) | 100-200W | continuous overnight |
| Laptop | 40-90W | varies by model |
| Desktop computer | 150-300W | varies by GPU |
| TV (50-inch LED) | 60-120W | continuous on |
| WiFi router + modem | 10-20W | continuous on |
| LED bulb | 8-15W each | continuous on |
| Ceiling fan | 30-75W | continuous on |
| Box fan / floor fan | 30-100W | continuous on |
| Smartphone charging | 5-20W | 1-3 hours per charge |
| Microwave (1000W rated) | 1,000-1,500W | short bursts |
| Coffee maker (drip) | 800-1,200W | 5-10 min brew cycle |
| Toaster oven | 800-1,500W | short bursts |
| Hair dryer | 1,000-1,800W | short bursts |
| Window AC (5,000 BTU) | 400-500W | compressor cycling |
| RV rooftop AC (13,500 BTU) | 1,500W run, 3,000W surge | continuous use |
| Sump pump (1/3 HP) | 400-600W run, 1,500W surge | intermittent |
| Power tools (drill, saw) | 500-1,500W | short bursts |
Wattage figures cross-checked against the DOE Energy Saver appliance wattage chart and manufacturer specifications.
Two nights, two people, lights, phones, drone, no fridge.
Total: 345Wh × 1.25 buffer = 432Wh needed
Recommended: 300 to 500Wh unit (Jackery 300 Plus, EcoFlow RIVER 2 Max). No solar panel required for a weekend.
Fridge, lights, internet, CPAP, phone charging.
Total: 2,730Wh × 1.25 buffer = 3,413Wh needed
Recommended: 3,000Wh+ unit (Bluetti AC300+B300, EcoFlow Delta Pro, Jackery 3000 Pro). With 400W of solar input, this scales to 2-day backup in good sun.
Same essentials as Scenario 2, multiplied across 72 hours, with daily solar recharge.
Total: 5,000Wh+ unit with 400W solar
Recommended: Bluetti AC300 + 2 B300 batteries (6,144Wh) plus 400W solar, or EcoFlow Delta Pro Ultra (6,144Wh) plus 800W solar. For 5+ day outages, stack additional batteries.
Watt-hours measure storage capacity. AC output watts measure how much you can run at once. A 2,000Wh unit with a 1,800W inverter cannot run a 2,200W microwave even if it has plenty of stored energy. Always check both numbers: the watt-hours for total runtime and the AC continuous + surge for compatibility with high-draw devices. For motor-driven appliances (pumps, refrigerators on startup, power tools), check the surge wattage, which is usually 1.5x to 2x the continuous rating.
To recharge a solar generator from solar in a single day of decent sun, match the panel wattage to roughly 20 to 25% of the battery capacity. Examples:
Most units cap their solar input lower than these targets, so always check the maximum solar input spec before adding more panels. The Jackery 1000 Plus accepts up to 1,000W of solar (best in its class). The EcoFlow Delta 2 caps at 500W.
Use this formula: device wattage times hours of use equals watt-hours needed. Example: a 60W fridge running 24 hours equals 1,440Wh per day. A 40W CPAP for 8 hours equals 320Wh per night. Add up every device you want to run. Multiply the total by 1.25 to account for inverter losses (about 15 to 20%) and unexpected draw. That number is the minimum solar generator capacity for one day of use.
For weekend car camping with lights, phone charging, and a 12V cooler: 200 to 500Wh works. For a long weekend with a small fan, laptop, drone, camera batteries, and lights: 500 to 800Wh. For a week-long trip with a 12V fridge, lights, fan, and electronics: 1,000 to 1,500Wh paired with a 100W to 200W solar panel for daily recharge.
For 24-hour essentials backup (fridge, lights, modem, CPAP, phones): 1,500 to 2,000Wh. For 72-hour backup with the same essentials: 4,000 to 5,000Wh. For week-long outage planning: 8,000 to 12,000Wh expandable system. The minimum useful size for home backup is about 1,500Wh because anything smaller cannot run a refrigerator overnight.
About 8 to 12 hours for a full-size kitchen refrigerator. The math: a typical fridge averages 100W (cycling on and off), so 1,000Wh divided by 100W equals 10 hours of running average. Inverter losses (about 15%) bring real runtime to 8 to 9 hours. A mini fridge at 50W average runs 17 to 20 hours on a 1,000Wh unit.
A 200W panel charges a 1,000Wh unit in about 5 hours of full sun. A 100W panel takes 10 hours. A 400W panel array (two 200W panels) takes 2.5 to 3 hours. Real conditions (clouds, angle, heat) add 25 to 40% to those times. For consistent daily recharge during multi-day use, match the panel wattage to about 20 to 25% of the unit's total Wh capacity.
Yes. Solar generators have AC inverters that convert stored DC battery power to AC for outlets. The conversion is 80 to 90% efficient. A 1,000Wh battery delivers 800 to 900Wh of usable AC power. Multiply your raw Wh calculation by 1.25 to account for this loss and you get a more accurate target capacity. DC outputs (12V car port, USB-A, USB-C) skip the inverter and avoid this loss.
No, not directly. Two solar generators cannot be cabled together in series or parallel to combine their output. What you can do is run different devices on each unit (fridge on one, lights and electronics on the other), or buy a single expandable model that accepts dedicated expansion batteries. The Bluetti AC300, EcoFlow Delta Pro, and Anker SOLIX F2000 all support expansion battery stacking.
Mostly accurate at moderate loads. Manufacturers test at controlled temperatures and steady draws. Real-world conditions reduce usable capacity by 10 to 20%. A 1,000Wh rated unit typically delivers 800 to 900Wh in practice. Battery aging also reduces capacity by 1 to 3% per year for LFP and 3 to 6% per year for NMC. Use the rated capacity as a maximum, not a target.
Got your target capacity? Now pick the model.
We rank solar generators by use case so you can match capacity to the right product.
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