Convert battery capacity from amp-hours (Ah) to watt-hours (Wh) and back in seconds. Use this calculator for solar systems, RV batteries, marine electronics, DIY power stations, UPS backups, and off-grid planning.
Formula: Wh = Ah × V. For real-world energy, you can include depth of discharge and efficiency.
Tip: Typical nominal voltages are 12V, 24V, 36V, and 48V systems.
If you are comparing batteries, planning solar storage, or checking runtime for appliances, an amp hours to watt hours calculator is one of the most useful tools you can use. Amp-hours (Ah) tell you electrical charge, while watt-hours (Wh) tell you energy. Most real-world power planning is easier in watt-hours because devices are usually rated in watts.
The core conversion is simple:
Watt-hours (Wh) = Amp-hours (Ah) × Voltage (V)
To convert back:
Amp-hours (Ah) = Watt-hours (Wh) ÷ Voltage (V)
This is why Ah alone is not enough to compare batteries across different voltage systems. A 100 Ah battery at 12V and a 100 Ah battery at 24V do not store the same total energy. The 24V battery stores roughly double the watt-hours.
Amp-hours measure current over time. Watt-hours measure power over time. Since power equals volts times amps, voltage must be included for a meaningful energy comparison. In plain language: voltage tells you how much “push” the battery has, and amp-hours tell you how long it can deliver current. Together, they define stored energy.
| Battery Capacity | Voltage | Energy (Wh) | Energy (kWh) |
|---|---|---|---|
| 100 Ah | 12 V | 1,200 Wh | 1.2 kWh |
| 100 Ah | 24 V | 2,400 Wh | 2.4 kWh |
| 100 Ah | 48 V | 4,800 Wh | 4.8 kWh |
| 200 Ah | 12 V | 2,400 Wh | 2.4 kWh |
The adjusted result is especially useful for real-world planning. Nominal ratings do not always equal usable energy once discharge limits, inverter losses, wiring, and temperature effects are considered.
Example A: 12V RV battery
A 100 Ah, 12V battery has 1,200 Wh nominal energy. If you plan for 90% usable capacity and 90% system efficiency, usable energy is roughly:
1,200 × 0.90 × 0.90 = 972 Wh.
Example B: 24V solar battery bank
200 Ah at 24V gives 4,800 Wh nominal. At 95% usable and 92% efficient system:
4,800 × 0.95 × 0.92 = 4,195 Wh usable (approx).
Example C: Convert Wh demand to Ah requirement
If your daily load is 3,000 Wh and your battery system is 24V, required nominal Ah is:
3,000 ÷ 24 = 125 Ah (before adding reserve margin).
Not all stored energy should be used every cycle. Battery chemistry and system design affect how much energy is practical and healthy to draw.
General rule:
Usable Wh = Ah × V × (DoD/100) × (Efficiency/100)
For conservative planning, many users add extra buffer beyond this number, especially for low temperatures, aging batteries, and surge loads.
Battery bank wiring changes voltage and amp-hours differently:
Example with two identical 12V 100Ah batteries:
Same total nominal energy, different system voltage. The preferred layout depends on inverter design, cable sizing, and charge controller compatibility.
To choose the right battery size, estimate your daily consumption in Wh and convert to Ah at your target voltage.
Quick formula:
Required Ah = Daily Wh ÷ V ÷ (DoD × Efficiency)
Where DoD and Efficiency are decimal values (for example, 0.9 and 0.9).
Use Ah when discussing battery ratings within the same voltage class. Use Wh when comparing different systems or calculating device runtime. If your appliances are in watts, watt-hours make planning much more accurate and straightforward.
Once you convert capacity to Wh, runtime is simple:
Runtime (hours) = Battery Wh ÷ Load W
Example: A usable 960 Wh battery running a 120W load lasts about 8 hours, assuming steady demand and no additional losses beyond what is already included in usable Wh.
It depends on voltage. At 12V, 100Ah is 1,200Wh. At 24V, it is 2,400Wh. At 48V, it is 4,800Wh.
No. Voltage is required. Ah alone does not represent total energy.
Not always. Usable energy is reduced by depth-of-discharge limits and system losses.
Wh is better for cross-voltage comparisons and runtime calculations. Ah is useful within the same voltage system.
Use Ah = Wh ÷ V. For example, 2,400Wh at 24V equals 100Ah.
An amp hours to watt hours calculator gives you fast, practical insight into battery energy capacity. The key principle is always the same: multiply amp-hours by voltage for nominal watt-hours, then adjust for real-world usable capacity. Whether you are designing an off-grid solar system, selecting a backup battery, or simply comparing products, converting Ah to Wh makes your decisions clearer and more accurate.