Quick answer
The selected battery provides about 30 hr 27 min of planned fridge runtime before solar or recharging. The default 512 Wh power station keeps 10% in reserve, uses a 95% DC efficiency estimate, and plans for 345 Wh of fridge energy per day after a heat and usage margin.
- Usable battery
- 438 Wh
- No-solar runtime
- 30 hr 27 min
- Average load
- 14.4 W
- Two-day battery
- 807 Wh
How to use this portable fridge battery runtime calculator
Start with battery energy. Enter watt-hours when the power station lists Wh, or enter amp-hours and nominal voltage for a separate battery. A 100 Ah battery is not automatically equivalent to a 100 Ah battery at another voltage, which is why the calculator converts Ah to Wh before estimating runtime.
Next, enter the average portable fridge energy use. Measured Wh per day is the best input because it includes compressor cycling. If you only know running watts, estimate the percentage of time the compressor runs and add a margin for hot weather, freezer mode, ventilation, and lid opening.
Finally, select DC or AC, set the battery reserve, and enter the number of days you need. Add solar only when you want to compare daily fridge use with expected daily panel production. For a household AC refrigerator and compressor startup check, use the Refrigerator Power Station Runtime Calculator.
Portable fridge battery runtime formula
battery Wh = battery Ah x nominal voltageusable battery Wh = rated Wh x (1 - reserve %) x connection efficiencydaily fridge Wh = measured Wh/day, or running W x duty cycle x 24planned daily Wh = daily fridge Wh x (1 + usage margin %)runtime hours = usable battery Wh / planned daily Wh x 24solar Wh/day = panel W x peak sun hours x solar efficiencynet daily battery draw = max(planned daily Wh - solar Wh/day, 0)Runtime is an energy calculation, not a guarantee that every day will match the same compressor cycle. The solar result is kept separate from the no-solar result so good-weather production does not hide the actual standalone battery runtime.
Methodology and assumptions
Portable compressor fridges turn on and off. Their maximum or rated current is therefore not the same as average battery use. This calculator keeps capacity, compressor cycling, conversion loss, reserve, and solar production as separate values so each assumption can be checked.
- Daily Wh or average Ah/h from a product specification, battery monitor, or fridge app is preferred over maximum current.
- Battery reserve represents energy intentionally left unused; it is not counted as energy delivered to the fridge.
- Connection efficiency includes DC wiring or AC inverter loss. It can be edited when measured system efficiency is known.
- The usage margin increases expected consumption instead of pretending that one laboratory condition fits every trip.
- Solar production uses peak sun hours and a system-efficiency factor. Shade and weather still require battery reserve.
Example calculations
Example: 100 Ah LiFePO4 battery and a 12V fridge
A 100 Ah, 12.8 V LiFePO4 battery stores 1,280 Wh. With 10% reserve and 95% DC connection efficiency, the calculator estimates 1,094 Wh available to the fridge.
If measured fridge use is 300 Wh per day and a 15% margin is added, planned use becomes 345 Wh per day. Estimated no-solar runtime is 3.2 days, so the modeled three-day target is covered.
How to find real portable fridge energy use
The strongest input is a 24-hour energy reading taken in similar weather and at the same fridge or freezer setpoint. Use Wh/day directly. If the specification lists average Ah/h at 12 V, multiply Ah/h by 12 V and 24 hours to estimate Wh/day.
Do not confuse average consumption with rated input current. The rated value is useful for fuse, connector, and cable planning, but treating it as a continuous 24-hour load can greatly overstate battery use for a cycling compressor fridge.
Portable fridge battery runtime chart
These examples show no-solar runtime before an added heat margin. Power stations use 10% reserve and 90% efficiency; the LiFePO4 example uses 10% reserve, and the lead-acid example uses 50%.
| Battery setup | Usable energy | At 250 Wh/day | At 400 Wh/day |
|---|---|---|---|
| 500 Wh power station | 405 Wh | 1.6 days | 1.0 days |
| 100 Ah 12.8 V LiFePO4 | 1,094 Wh | 4.4 days | 2.7 days |
| 100 Ah 12 V lead-acid | 570 Wh | 2.3 days | 1.4 days |
| 1,500 Wh power station | 1,215 Wh | 4.9 days | 3.0 days |
Can solar keep a portable fridge running?
Solar can replace part or all of the average daily fridge use when panel watts, peak sun hours, and system efficiency produce enough Wh per day. The battery still has to carry the fridge overnight and through clouds, shade, and poor panel orientation.
Use this calculator for the daily energy balance, then use the Solar Charging Time Calculator when you need to estimate how long the panel takes to restore a specific battery percentage.
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FAQ
How long will a 100Ah battery run a 12V fridge?
It depends on battery voltage, usable depth of discharge, connection loss, and the fridge's daily energy use. A 100 Ah 12.8 V LiFePO4 battery with 10% reserve and 95% DC efficiency provides about 1,094 Wh of usable energy. At a planned 345 Wh per day, that is about 3.2 days. A lead-acid battery with the same Ah rating usually has much less planned usable capacity when a 50% reserve is kept.
How long will a 500Wh power station run a portable fridge?
A 500 Wh power station with 10% reserve and 90% output efficiency provides about 405 Wh to the fridge. That is about 1.6 days at 250 Wh per day, or about one day at 400 Wh per day. Hot weather, freezer operation, and frequent opening can shorten the result.
Should I enter rated watts or Wh per day?
Use measured Wh per day, average Ah per hour, or the fridge app's energy history when available. Rated current or maximum watts are mainly useful for wiring and peak-load checks; they do not show how often the compressor cycles. Use watts plus duty cycle only when an average energy figure is unavailable.
Is a 12V DC connection better than using the AC outlet?
A direct 12V or 24V DC connection usually avoids an extra inverter conversion, so it often leaves more battery energy for the fridge. Actual performance still depends on cable size, connector quality, voltage drop, and the power station's own DC output behavior.
What size solar panel will keep a portable fridge running?
Divide planned daily fridge energy by peak sun hours and solar-system efficiency. A fridge using 345 Wh per day with 4.5 peak sun hours and 75% system efficiency needs about 102 W of panel capacity for average daily break-even. More panel and battery reserve are needed for clouds, shade, poor angle, and shorter winter days.
Does a portable fridge use more power in hot weather?
Yes. Higher ambient temperature, a lower internal setpoint, freezer mode, poor ventilation, warm food, and frequent lid opening can increase compressor run time. Add a planning margin or use measured consumption from conditions similar to the trip you are planning.
Can I run a portable fridge from a car starter battery?
It may be electrically possible, but repeated deep discharge can leave the vehicle unable to start and can shorten starter-battery life. A protected auxiliary battery, portable power station, or deep-cycle system is usually a more practical planning basis. Follow the vehicle, fridge, and battery instructions.
Does solar make the runtime unlimited?
No. A positive average daily energy balance only means the entered panel can replace the modeled daily use under the entered sun conditions. Clouds, shade, nighttime load, charge-controller limits, high heat, and several poor-weather days can still discharge the battery.