Ah to kWh Calculator
Convert battery capacity between amp-hours (Ah) and kilowatt-hours (kWh) using your bank voltage — the number datasheets and solar tools actually need.
~80–100% for LiFePO4, ~50% for lead-acid.
Nominal capacity. Usable energy applies your depth-of-discharge limit.
How this conversion works
kWh = Ah × Volts ÷ 1000 and Ah = kWh × 1000 ÷ Volts.Watt-hours
Wh = Ah × Volts. Usable energy = kWh × depth-of-discharge. A 48V bank stores four times the energy of a 12V bank at the same amp-hours.Amp-hours are not energy — until you add voltage
Amp-hours measure charge, not energy. A 100 Ah battery at 12V holds a quarter of the energy of a 100 Ah battery at 48V, even though the amp-hour number is identical. To compare batteries or feed a battery bank or off-grid calculator, convert to watt-hours or kilowatt-hours by multiplying by the voltage.
Worked example
A 100 Ah 12V battery holds 100 × 12 = 1,200 Wh = 1.2 kWh nominal. At an 80% depth of discharge you can safely use about 0.96 kWh. The same 100 Ah at 48V holds 4.8 kWh.
Common battery sizes at a glance
| Battery | Nominal energy | Usable @80% DoD |
|---|---|---|
| 100 Ah · 12 V | 1.2 kWh | 0.96 kWh |
| 200 Ah · 12 V | 2.4 kWh | 1.9 kWh |
| 100 Ah · 24 V | 2.4 kWh | 1.9 kWh |
| 100 Ah · 48 V | 4.8 kWh | 3.8 kWh |
| 200 Ah · 48 V | 9.6 kWh | 7.7 kWh |
| 280 Ah · 51.2 V (LiFePO4 rack) | 14.3 kWh | 11.5 kWh |
Two batteries with the same amp-hours can differ four-fold in energy — always compare kWh, not Ah, when shopping. Lead-acid packs should generally use only ~50% of the nominal figures above.
Frequently asked questions
Multiply amp-hours by the battery voltage, then divide by 1,000. For example, 100 Ah at 12V is 100 x 12 / 1000 = 1.2 kWh.
Because amp-hours only measure charge. Energy (kWh) is charge times voltage, so the same amp-hours store very different energy at 12V, 24V or 48V.
It is the energy you can safely draw without damaging the battery, equal to total capacity times the depth of discharge. LiFePO4 allows 80 to 100%; lead-acid is usually limited to about 50%.
5 kWh is 5,000 Wh; divide by 48V to get about 104 Ah of nominal capacity.
Sources & standards
This calculator converts amp-hours to energy using the same SI unit definitions and battery-capacity terminology found on datasheets and in electrical codes.
- SI Units — Electric Current — National Institute of Standards and Technology (NIST)
Defines the ampere, the base SI unit the amp-hour figures in this calculator are built on. - NIST Special Publication 811 — Guide for the Use of the International System of Units (SI) — NIST
Sets the conversion conventions used to turn Ah × V into watt-hours and kilowatt-hours. - IEC 61427-1 — Secondary cells and batteries for renewable energy storage — International Electrotechnical Commission
Standardizes how rated and usable capacity are tested and reported for the solar batteries this tool converts. - NFPA 70 (National Electrical Code), Article 706 — Energy Storage Systems — National Fire Protection Association
Governs how the battery banks this kWh figure feeds into are installed and rated in the US.