How Long Will a 100Ah Battery Last?
A 100Ah battery is one of the most common sizes for portable power, RV house systems, marine applications, and small solar setups. Understanding its real-world runtime helps you plan systems that actually meet your needs.
Energy by Voltage
A 100Ah rating tells you charge capacity, but energy depends on voltage. The same 100Ah rating at different voltages stores vastly different amounts of energy:
| Voltage | Total Energy | Usable (80% DoD) |
|---|---|---|
| 12.8V (4S LFP) | 1,280 Wh | 1,024 Wh |
| 25.6V (8S LFP) | 2,560 Wh | 2,048 Wh |
| 51.2V (16S LFP) | 5,120 Wh | 4,096 Wh |
Runtime Formula
Runtime Table: 100Ah 12.8V LFP
At 80% DoD and 90% system efficiency, a 100Ah 12.8V LFP battery provides 1,024 Wh of usable energy:
| Load | Power (W) | Runtime |
|---|---|---|
| Phone charging | 15 W | ~60 hours |
| LED lights (×4) | 24 W | ~38 hours |
| Laptop | 60 W | ~15 hours |
| 12V camping fridge | 50 W | ~18 hours |
| TV + streaming | 100 W | ~9.1 hours |
| Coffee maker | 800 W | ~1.1 hours |
| Space heater | 1,500 W | ~36 minutes |
Chemistry Comparison
| Chemistry | Usable DoD | Usable Energy | Runtime at 100W |
|---|---|---|---|
| LFP (LiFePO4) | 80% | 1,024 Wh | ~9.2 hrs |
| NMC (Lithium) | 80% | 1,024 Wh | ~9.2 hrs |
| AGM Lead-Acid | 50% | 640 Wh | ~5.8 hrs |
| Flooded Lead-Acid | 50% | 640 Wh | ~5.0 hrs* |
* Flooded lead-acid runtime is lower due to Peukert effect at moderate discharge rates.
Worked Example
Given: 100 Ah at 12.8V LFP, 80% DoD, 90% efficiency, 150W AC load
Step 1: Usable energy:
Step 2: Effective load:
Step 3: Runtime:
Try It
Use the Runtime Calculator for your specific load and battery configuration.
Open Runtime CalculatorRelated Articles
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Runtime examples for 200Ah batteries across RV, marine, and home backup loads.
Read Guide →How Long Will a Battery Last?
The general method for calculating runtime from any capacity and load.
Read Guide →Frequently Asked Questions
How long will a 100Ah battery run a 1000W inverter?
A 100Ah 12.8V LFP battery at 80% DoD provides 1,024 Wh of usable energy. Through a 90% efficient inverter, the effective load is 1,111W. Runtime is approximately 0.92 hours, or about 55 minutes.
How long will a 100Ah lead-acid battery last?
Lead-acid batteries have lower usable capacity (50% DoD) and suffer the Peukert effect at higher loads. A 100Ah AGM battery at 50% DoD provides only 640 Wh usable. At 100W, runtime is about 5.8 hours — roughly half that of a comparable LFP battery.
How many solar panels to recharge a 100Ah battery?
A 100Ah 12.8V LFP battery stores 1,280 Wh. A 200W solar panel in 5 peak sun hours generates about 900 Wh (accounting for losses). You need approximately two 200W panels or one 300W panel to fully recharge in one day.
Can a 100Ah battery run a refrigerator?
A typical 12V camping fridge draws 40–60W average (compressor cycles). A 100Ah LFP battery at 80% DoD provides 1,024 Wh. At 50W average, runtime is about 16.4 hours. For a full-size residential fridge (150W average), runtime drops to about 5.5 hours.