Ah to kWh Calculator
Convert battery amp-hours (Ah) to kilowatt-hours (kWh). Accounts for system voltage and battery chemistry Depth of Discharge (DoD) to show true usable energy.
Based on 90% DoD for LiFePO4. This is the actual energy available before reaching safe discharge limits.
Raw electrical energy at 100% total discharge (Ah × V / 1,000). Equal to 4,800 Watt-hours (Wh).
Why Amp-Hours (Ah) Alone Don't Tell the Whole Energy Story
Amp-hours (Ah) measure electric charge volume over time, but energy storage depends equally on system voltage. A 100Ah 12V battery holds only 1.2 kWh of energy, whereas a 100Ah 48V battery holds 4.8 kWh — four times as much energy in the exact same amp-hour rating! When sizing solar battery banks or inverter power systems, converting Ah to kilowatt-hours (kWh) provides the true metric of stored energy. To convert small battery ratings, use our mAh to Wh calculator or convert larger loads with the kW to Amps calculator.
Ah to kWh Conversion Formula
Multiply battery capacity in amp-hours (Ah) by nominal system voltage (V) to find total watt-hours, then divide by 1,000 to yield kilowatt-hours (kWh).
Depth of Discharge (DoD) reflects how much battery capacity can be safely drawn without damaging internal cells or degrading lifespan.
Depth of Discharge (DoD) & Chemistry Reference
Discharging a battery completely (100% DoD) rapidly degrades most chemical cells. The table below lists recommended maximum discharge thresholds to maximize battery cycle life:
| Battery Chemistry | Rec. Max DoD | Typical Cycle Life | Usable Energy from 100Ah @ 12V |
|---|---|---|---|
| LiFePO4 (Lithium Iron Phosphate) | 80% – 90% | 3,000 – 6,000+ cycles | 1.08 kWh (at 90% DoD) |
| Lithium-ion NMC / NCA | 80% | 1,000 – 2,000 cycles | 0.96 kWh (at 80% DoD) |
| AGM / Gel Sealed Lead-Acid | 50% | 500 – 1,000 cycles | 0.60 kWh (at 50% DoD) |
| Flooded Lead-Acid (Deep Cycle) | 50% | 300 – 800 cycles | 0.60 kWh (at 50% DoD) |
Frequently Asked Questions
A 100Ah 12V battery has a theoretical energy capacity of 1.2 kWh (100 Ah × 12 V / 1,000 = 1,200 Wh). However, usable energy depends on chemistry: a 12V 100Ah LiFePO4 battery (90% DoD) yields ~1.08 kWh usable energy, whereas a 12V 100Ah lead-acid battery (50% DoD) yields only ~0.60 kWh.
A 48V 100Ah battery stores 4.8 kWh of theoretical energy (100 Ah × 48 V / 1,000). In a LiFePO4 server rack battery with 90% recommended Depth of Discharge, net usable energy is 4.32 kWh (or ~5.12 kWh for a 51.2V nominal lithium rack).
Lithium Iron Phosphate (LiFePO4) batteries provide 80% to 90% usable energy relative to nameplate capacity. Unlike lead-acid batteries which experience voltage sag below 50% discharge, LiFePO4 maintains flat voltage delivery across 90% of its discharge curve.
Amp-hours measures electric charge capacity, not total work capability. Energy requires accounting for voltage. A 100Ah 48V battery holds four times as much energy (4.8 kWh) as a 100Ah 12V battery (1.2 kWh). If converting small consumer batteries, check our Wh to mAh converter.
Methodology & Calculation Logic
This tool computes capacity client-side using standard electrical engineering conversion principles:
- 1. Watt-Hour Calculation: $\text{Wh} = \text{Ah} \times V_{\text{nominal}}$
- 2. Kilowatt-Hour Conversion: $\text{kWh}_{\text{theoretical}} = \frac{\text{Wh}}{1000}$
- 3. Usable Capacity Application: $\text{kWh}_{\text{usable}} = \text{kWh}_{\text{theoretical}} \times \frac{\text{DoD\%}}{100}$