kWh to Ah Calculator
Convert battery energy (kWh) to capacity (Ah) at a specific voltage.
What this calculator does
This tool converts kilowatt-hours (kWh) into amp-hours (Ah) using your battery or system voltage. If you use a battery bank for solar, RV, marine, backup power, or off-grid projects, this conversion is one of the most useful sizing calculations.
The core equation is simple: Ah = (kWh × 1000 × efficiency) ÷ voltage. Because 1 kWh = 1000 Wh, dividing watt-hours by volts gives amp-hours.
kWh vs Ah: quick explanation
kWh (energy)
kWh measures total energy over time. Utility bills use kWh because it tells you how much work can be done overall.
Ah (charge capacity)
Ah measures electric charge. Battery labels often use Ah because it tells you how much current a battery can provide over time. The same kWh value can correspond to different Ah values at different voltages.
Why voltage matters
For the same energy, higher voltage means lower Ah. Lower voltage means higher Ah. This is why a 48V battery bank usually has fewer Ah than a 12V bank with the same kWh rating.
| Energy | Voltage | Approx. Capacity |
|---|---|---|
| 1 kWh | 12V | 83.33 Ah |
| 1 kWh | 24V | 41.67 Ah |
| 1 kWh | 48V | 20.83 Ah |
Step-by-step conversion method
- Start with battery energy in kWh.
- Convert kWh to Wh by multiplying by 1000.
- Apply efficiency (optional but realistic for system losses).
- Divide by system voltage.
- Result is Ah.
Example 1
You have a 5 kWh battery at 48V and assume 95% usable efficiency:
Ah = (5 × 1000 × 0.95) ÷ 48 = 98.96 Ah
Example 2
You have a 2.4 kWh battery at 12V with 100% efficiency:
Ah = (2.4 × 1000) ÷ 12 = 200 Ah
Practical tips for battery sizing
- Use nominal voltage: 12V, 24V, 36V, 48V, etc., unless you are modeling exact operating voltage.
- Include losses: Inverter and wiring losses can reduce real-world usable capacity.
- Check depth of discharge: Not all chemistries should be discharged to 0%.
- Match to load profile: Peak current and runtime both matter, not just total Ah.
Frequently asked questions
Can I convert kWh to Ah without voltage?
No. Voltage is required. kWh is energy; Ah is charge. Voltage links the two.
Is this valid for lithium and lead-acid batteries?
Yes for basic conversion. But usable Ah in practice depends on battery chemistry, discharge limits, and temperature.
What efficiency value should I use?
Use 100% for ideal math only. For real systems, many people use 85% to 95% depending on inverter quality, wiring, and conversion path.
Bottom line
If you know your energy in kWh and your system voltage, you can quickly estimate battery capacity in Ah. Use the calculator above to size battery banks, compare options, and sanity-check design assumptions before purchase.