Amp-hours are derived—not guessed—from watt-hours and voltage. This guide shows how to calculate amp-hours from watt-hours using the nominal volts your bank will run at.
Benefits
- Formula: Ah = Wh ÷ nominal voltage.
- Convert kWh budgets to Wh, then to Ah at your system voltage.
- Reverse check: Wh = Ah × V to verify pack listings.
How it works
- Start with watt-hours—daily load total, solar storage target, or pack energy rating.
- Divide by nominal bus voltage (12 V, 24 V, 48 V, etc.).
- Read required amp-hours for bank sizing and product shortlists.
FAQ
How do I calculate amp-hours from watt-hours?
Ah = Wh ÷ V. Example: 3,840 Wh target at 12 V → 3,840 ÷ 12 = 320 Ah bank. At 48 V the same energy needs 3,840 ÷ 48 = 80 Ah—always state voltage with the result.
How do I convert kWh to Ah?
First kWh × 1,000 = Wh, then Ah = Wh ÷ V. Example: 5 kWh = 5,000 Wh at 48 V → 5,000 ÷ 48 ≈ 104 Ah. Skipping the Wh step is a common spreadsheet error.
Should I add margin after calculating Ah?
Yes—this gives rated equivalence only. Apply depth-of-discharge (e.g., need 320 Ah rated for 256 Ah usable at 80% DoD) and inverter/charging efficiency before final purchase. Calculate base Ah from Wh first, then inflate for real-world losses.
Technical specifications
- Ah = Wh ÷ nominal_V.
- Wh from kWh: Wh = kWh × 1,000.
- Required rated Ah ≈ (usable Wh ÷ DoD) ÷ V.
- Related: wh-to-ah-converter, ah-to-wh, battery-bank-size.