# 12V Fridge Battery Runtime Calculator (with Solar)

> Free 12V fridge battery runtime calculator: how many hours a lithium, AGM battery or power station runs your portable fridge at your temperatures, and how…

- Source: https://portablefridgeguide.com/tools/battery-runtime-calculator/
- Markdown version: https://portablefridgeguide.com/tools/battery-runtime-calculator.md

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# How long will your battery run your fridge?
Pick your fridge, your weather and your battery or power station. We'll estimate the hours on battery alone, what you use per day and how much solar keeps it running.

Your fridgeCustom — I know the average drawAlpicool C20Anker SOLIX EverFrost 2 40LBougeRV 23 Quart (CR22)BougeRV CRD2 V2.0 43QT with 240Wh BatteryDometic CFX2 28Dometic CFX5 55IMDometic CFX5 75DZEcoFlow GLACIER Classic 35LEUHOMY 59QT 12V RefrigeratorICECO GO20ICECO VL45 ProSICECO VL60 Dual ZoneICECO VL75 ProD
Average draw at 90°F (Ah/h at 12 V)

Outside temperature 85°F
Fridge settingFridge — 37°FCold fridge — 33°FFreezer — 10°FDeep freeze — 0°F

Power source12V LiFePO4 lithium battery12V AGM / lead-acid battery12V lithium NMC batteryPortable power station (Wh)
Battery capacity (Ah)

Solar panel watts none
Peak sun hours per day3 — winter, cloudy or shaded4 — mixed5 — typical summer6 — desert summer

## The method
Runtime = usable battery amp-hours ÷ the fridge's average draw (amp-hours per hour at 12 V). This is the method Dometic publishes for its CFX fridges. Three details make the difference between a good estimate and a dead battery:

- **Average draw, not rated input.** A compressor cycles on and off. We use each maker's published average draw where it exists, measured at a stated outside and inside temperature.
- **Temperature gap.** The compressor works harder the bigger the gap between outside air and the fridge setting, so we scale the published figure by that gap, and add a penalty below freezing because compressors get less efficient as they run colder (fitted to EcoFlow's published fridge and freezer figures). A freezer at 0°F on a 95°F day uses roughly two and a half times what a fridge at 37°F does.
- **Usable capacity.** Lead-acid and AGM batteries should only be drained to about 50%, lithium NMC about 80%, LiFePO4 about 90%; power stations lose some energy in conversion, so we use 85% of their rated Wh.
Solar is estimated as panel watts × peak sun hours × 0.75 to allow for controller, wiring and panel-angle losses. For the background, read [how long a battery runs a 12V fridge](https://portablefridgeguide.com/posts/how-long-will-a-battery-run-a-12v-fridge/), [fridge power consumption explained](https://portablefridgeguide.com/posts/portable-fridge-power-consumption-explained/) and [what size solar panel you need](https://portablefridgeguide.com/posts/solar-panel-size-for-12v-fridge/).

  How long a battery runs a 45-quart fridge Estimated hours with no recharging, fridge set to 37°F, lid mostly closed. Based on Dometic's published 1.03 Ah/h for the CFX3 45 at 90°F, scaled by temperature.

| Battery | 70°F outside | 85°F outside | 100°F outside |
| --- | --- | --- | --- |
| 100 Ah AGM / lead-acid | 3.1 days | 2.1 days | 39 hr |
| 50 Ah LiFePO4 | 2.8 days | 46 hr | 35 hr |
| 100 Ah LiFePO4 | 5.6 days | 3.8 days | 2.9 days |
| 1,000 Wh power station | 4.4 days | 3.0 days | 2.3 days |

  Usable capacity: lead-acid/AGM 50%, LiFePO4 90%, power station 85%. At 85°F the same fridge needs roughly 80 W of solar with 5 peak sun hours to break even. Your fridge, your settings: [run the calculator](https://portablefridgeguide.com/tools/battery-runtime-calculator/).

## A worked example
Dometic publishes an average draw of 1.03 Ah/h for its CFX3 45 at 32°C (90°F) outside and 4°C (39°F) inside. Take an 85°F day with the fridge at 37°F. The temperature gap shrinks from 28°C to about 26.7°C, so the estimated draw is 1.03 × 26.7 ÷ 28 ≈ 0.98 Ah/h, or about 283 Wh per day.
A 100 Ah LiFePO4 battery gives about 90 Ah usable, so it runs the fridge for 90 ÷ 0.98 ≈ 92 hours (about 3.8 days) with no charging. To replace283 Wh a day with 5 peak sun hours, you need 283 ÷ 5 ÷ 0.75 ≈ 75 W of solar, which is why a 100 W panel is the usual minimum and 150–200 W gives margin for clouds. These are illustrative numbers from one published spec; your fridge, loading and weather will differ.

## Frequently asked questions

### How long will a 100Ah battery run a 12V fridge?
A 100 Ah LiFePO4 battery (about 90 Ah usable) runs an efficient 45-quart compressor fridge such as the Dometic CFX3 45 for roughly 5 days at 70°F outside and about 3½ days at 90°F, with the fridge at 37°F. Less efficient fridges get less. A 100 Ah AGM battery gives about half that, because you should only use about 50% of a lead-acid battery's capacity.

### How do I work out my fridge's power draw?
Use the average draw, not the rated input. Makers like Dometic publish average amp-hours per hour at a stated temperature (for example 1.03 Ah/h at 90°F outside and 39°F inside for the CFX3 45). The rated input (often 45–100 W) is the maximum while the compressor runs; it only runs part of the time.

### How much solar do I need for a 12V fridge?
Divide the fridge's daily watt-hours by your peak sun hours, then add about a third for losses. A fridge using 300 Wh a day with 5 sun hours needs roughly 80 W of panel on paper; in practice 100–200 W of solar is common for one fridge because clouds, shade and panel angle cut output.

### Can I run a portable fridge off my car's starter battery?
For a few hours, yes, and the fridge's battery protection setting will switch it off before the battery is too flat to start the engine (set it to High on a starter battery). For overnight stops, a separate battery or power station is the safer choice.

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