Amp Hours to Watt Hours Calculator
| Amp Hours | 12V (Wh) | 24V (Wh) | 48V (Wh) |
|---|---|---|---|
| 20 Ah | 240 | 480 | 960 |
| 50 Ah | 600 | 1,200 | 2,400 |
| 100 Ah | 1,200 | 2,400 | 4,800 |
| 200 Ah | 2,400 | 4,800 | 9,600 |
Amp Hours to Watt Hours Formula & Engineering Explanation
Wh = Ah × Voltage Explained
Converting amp hours to watt hours multiplies the charge capacity by voltage to determine total energy. The formula Wh = Ah × V tells you how much energy a battery stores. A 100Ah battery at 12V stores 1,200Wh (1.2kWh) of energy.
Power Output vs Energy Storage
Amp hours measure charge capacity (how long a battery can deliver current), while watt hours measure total energy (capacity × voltage). For battery energy formulas, visit our Wh to Ah converter.
Metric to Imperial Energy Unit Conversion
In the imperial system, energy is sometimes measured in BTU (British Thermal Units). 1 Wh = 3.412 BTU. Our conversion tools focus on the electrically relevant units used in modern battery systems.
Calculating Runtime Using Amp Hour Conversion
UPS Backup Power Calculations
To calculate UPS runtime: Runtime (hours) = Battery Wh ÷ Load (W). A 1500VA UPS with a 12V 9Ah battery has 108Wh. At 50% load (375W with efficiency losses), runtime ≈ 12-15 minutes.
RV & Marine Battery Energy Estimation
RV batteries are typically 12V deep-cycle batteries rated in Ah. A pair of 100Ah 12V batteries provides 2,400Wh (2.4kWh). For camping, this powers LED lights (10W × 6h = 60Wh), a phone charger (15W × 4h = 60Wh), and a small fan (40W × 8h = 320Wh).
Generator Load Planning
Converting Ah to Wh helps determine generator sizing. If your daily consumption is 5,000Wh and your generator runs 6 hours/day, you need a generator producing at least 833W continuous output. For all battery formulas, see our battery conversion calculator.
Battery Chemistry Impact on Energy Conversion
Lithium-Ion vs Lead-Acid Comparison
Lithium-ion batteries have higher energy density (~150-250 Wh/kg) compared to lead-acid (~30-50 Wh/kg). A 100Ah lithium battery weighs roughly 10-13kg, while an equivalent lead-acid battery weighs 25-30kg.
Efficiency Loss Considerations
Real-world efficiency is never 100%. Lead-acid batteries deliver about 80-85% of rated capacity, while lithium-ion achieves 90-95%. Always account for these losses in system design. For milliamp hour conversions, see Wh to mAh converter.