Free calculator
RV Fridge Battery Calculator: How Long Will My Battery Run My Fridge?
Enter your fridge, battery and charging setup to see how many days you can run before the battery needs a recharge, and whether your solar keeps up.
Your result
–days without recharging
- Fridge use–
- Total daily use–
- Usable battery–
- Daily recharge–
- Net per day–
Enable JavaScript to use the calculator, or use the formula and tables below.
How the calculation works
- Fridge use per dayRunning current × 24 hours × duty cycle. Example: 3.5A × 24 × 45% = about 38Ah a day.
- Add the other loadsEverything else on the same battery: lights, water pump, phone charging, inverter idle draw.
- Usable batteryRated capacity × usable share (about 90% for lithium, 50% for AGM) × (1 − reserve).
- Days without rechargingUsable battery ÷ total daily use.
- Recharge per daySolar watts × sun hours × about 75% system efficiency ÷ 12.8V, plus DC-DC charger amps × hours driven. If it covers your daily use, the battery stops draining.
Quick reference: days of fridge power without recharging
Total daily use (fridge plus other loads) in amp-hours, with a 20% reserve kept. Rough figures; your results depend on weather, insulation and how often the door opens.
| Battery | 25Ah/day | 35Ah/day | 45Ah/day |
|---|---|---|---|
| 100Ah AGM | 1.6 days | 1.1 days | 0.9 days |
| 200Ah AGM | 3.2 days | 2.3 days | 1.8 days |
| 100Ah lithium | 2.9 days | 2.1 days | 1.6 days |
| 200Ah lithium | 5.8 days | 4.1 days | 3.2 days |
| 300Ah lithium | 8.6 days | 6.2 days | 4.8 days |
Getting more days from the same battery
- Pre-chill the fridge on shore power for 24 hours before the trip and load only cold food.
- Keep it ventilated and out of the sun. Duty cycle climbs fast when the fridge can’t shed heat.
- Use short, heavy cable on a dedicated fused circuit; voltage drop causes cutoffs while the battery still has charge.
- Set the fridge’s low-voltage cutoff to match your battery chemistry.
More in our guide to keeping an RV fridge cold on the road, and battery options in the RV batteries guide.
Frequently asked questions
How long will a 100Ah battery run a 12V fridge?
With a typical compressor fridge using about 25-35Ah a day and nothing else on the battery, a 100Ah lithium battery (about 90Ah usable, 72Ah after a 20% reserve) lasts roughly 2-3 days. A 100Ah AGM battery (about 50Ah usable) lasts only about 1-1.5 days. Hot weather, frequent door openings and other loads shorten that.
How many amp-hours does a 12V fridge use per day?
Multiply the current it draws while the compressor runs by 24 hours and by the share of time the compressor runs (the duty cycle). Example: 3.5A x 24h x 40% = about 34Ah a day. Duty cycle rises with outside temperature: roughly 25-30% in mild weather and 40-50% or more in the heat.
How much solar do I need to run a 12V fridge?
To replace about 30Ah a day you need roughly 400Wh of energy. At about 5 hours of good sun and typical system losses, that is around 100-150W of solar in summer, and more in winter or cloudy weather. Use the calculator to match your own numbers.
Is lithium or AGM better for running an RV fridge?
Lithium. You can use about 80-100% of a lithium battery's rated capacity, versus about 50% for AGM before you shorten its life, and lithium holds its voltage better under load, which avoids low-voltage fridge cutoffs.
Estimates only. Real consumption varies with the fridge model, temperature, insulation, door openings and wiring. Check your equipment’s specifications.