Convert kWh to Ah in Seconds
Use this calculator to convert energy in kilowatt-hours (kWh) into battery capacity in amp-hours (Ah). You can also account for system efficiency and depth of discharge for real-world battery bank sizing.
Formula used: Ah = (kWh × 1000) ÷ (V × Efficiency). For total bank size: Bank Ah = Ah ÷ DoD.
What does kWh to amp-hour conversion mean?
When you size a battery, you’ll often see energy listed in kilowatt-hours (kWh) and battery capacity listed in amp-hours (Ah). These units are related, but they are not the same thing:
- kWh tells you how much total energy is stored or consumed.
- Ah tells you how much current a battery can deliver over time at a given voltage.
Because voltage matters, there is no single universal conversion from kWh to Ah without specifying system voltage.
The kWh to Ah formula
The core conversion formula is:
Ah = (kWh × 1000) ÷ V
If you include efficiency losses (inverter, wiring, conversion losses), use:
Ah = (kWh × 1000) ÷ (V × efficiency)
Where efficiency is in decimal form (e.g., 90% = 0.90).
If you also want the total installed battery bank size based on allowable depth of discharge (DoD), use:
Battery Bank Ah = Required Ah ÷ DoD
Example: if you only use 80% of your battery (DoD = 0.80), you divide by 0.80 and need a larger bank.
Step-by-step examples
Example 1: 5 kWh at 48V
Ah = (5 × 1000) ÷ 48 = 104.17 Ah
So a 48V system needs about 104 Ah of usable capacity for 5 kWh.
Example 2: 2.4 kWh at 12V, 90% efficiency, 50% DoD
First calculate usable Ah with losses:
Ah = (2.4 × 1000) ÷ (12 × 0.90) = 222.22 Ah
Then account for DoD limit:
Battery bank Ah = 222.22 ÷ 0.50 = 444.44 Ah
This is why low-voltage systems and conservative DoD settings can require large battery banks.
Quick reference table (ideal, 100% efficiency)
| Energy (kWh) | 12V System (Ah) | 24V System (Ah) | 48V System (Ah) |
|---|---|---|---|
| 1 kWh | 83.33 Ah | 41.67 Ah | 20.83 Ah |
| 5 kWh | 416.67 Ah | 208.33 Ah | 104.17 Ah |
| 10 kWh | 833.33 Ah | 416.67 Ah | 208.33 Ah |
Choosing the right voltage for battery systems
Higher voltage systems generally need fewer amp-hours for the same kWh. That can reduce cable thickness, heat losses, and current stress. Typical patterns:
- 12V: small RV setups, boats, light off-grid use.
- 24V: medium-sized systems.
- 48V: larger residential solar and backup systems.
Always follow your inverter, charge controller, and battery manufacturer requirements before deciding system voltage.
Common mistakes to avoid
- Ignoring efficiency losses: Real systems are never 100% efficient.
- Skipping DoD limits: Especially important with lead-acid batteries.
- Mixing AC and DC assumptions: AC appliance usage should be converted properly through inverter efficiency.
- Forgetting surge loads: Startup currents can exceed average load requirements.
FAQ
Is kWh the same as Ah?
No. kWh is energy, Ah is charge capacity. You need voltage to convert between them.
Can I use this calculator for lithium batteries?
Yes. It works for lithium, lead-acid, AGM, and other chemistries. Just set realistic efficiency and DoD values for your setup.
What efficiency value should I use?
For rough planning, 85% to 95% is common depending on inverter quality, cable lengths, and charge/discharge path.
Bottom line
Converting kWh to Ah is simple once voltage is known, but practical battery sizing should include efficiency and depth of discharge. Use the calculator above to estimate both usable amp-hours and total recommended battery bank capacity for off-grid solar, backup power, RV, marine, or DIY energy storage projects.