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Free calculator

Use this calculator to

  • Convert a battery's Ah rating and nominal voltage into Wh or kWh
  • Size a battery bank for solar storage, UPS backup or off-grid loads
  • Compare batteries of different voltages on a like-for-like kWh basis
  • Work back from a kWh target to the Ah capacity needed at your system voltage

Ah to kWh / Wh Battery Converter

Convert between Ah, Wh, and kWh for batteries and energy storage systems.

Ah
V
Result
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kWh
V
Result
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Formulas

  • Wh = Ah × V
  • kWh = Ah × V / 1000
  • Ah = kWh × 1000 / V
  • e.g. 100Ah @ 12V = 1.2 kWh

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kWh→W

kWh to Watts

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Common scenarios

Select one to run it in the calculator above.

For business

Why this matters for businesses

Battery capacity gets quoted in three different units (Ah, Wh, kWh) by three different suppliers, often on the same project. For a business sizing a commercial BESS, an EV charging depot, or solar-plus-storage, the unit mismatch is where capex estimates start to wander. A 500 Ah string at 48 V is a very different proposition to a 500 Ah string at 400 V, and the kWh you actually own only becomes clear once the voltage is pinned down.

Storage economics are usually framed against peak avoidance, DSR revenue, or self-consumption of on-site generation. A site paying 70 p/kWh on a winter weekday peak and 12 p/kWh overnight has a clean arbitrage on every kWh of round-trip stored capacity, but only if the nameplate maths is right. A 200 kWh battery sized off a mis-converted Ah figure can mean 30% less usable energy than the model assumed, which is the difference between a 6-year payback and a 9-year payback.

Purely Energy's flex desk and Purely Insights platform sit on the contract side of the meter: tariff structure, capacity charges, DUoS bands, DSR availability windows and time-of-use signals. When a battery vendor proposes a system, we will sanity-check the energy maths against your actual half-hourly profile so the business case earns out against real consumption and real tariffs, not a brochure curve, and we will model the contract changes that turn a sized system into a returning investment.

Common questions

How do I convert Ah to kWh?

Multiply the amp-hour rating by the battery's nominal voltage to get watt-hours, then divide by 1,000: kWh = Ah x V / 1000. A 100 Ah battery at 12 V stores 1.2 kWh, while the same 100 Ah at 48 V stores 4.8 kWh. Always use the nominal pack voltage, not the peak charge voltage, or the energy figure will be overstated.

Why does the same Ah rating give a different kWh at different voltages?

Amp-hours only count charge, not energy. Energy is charge multiplied by voltage, so a higher-voltage pack stores more energy for the same Ah. That is why comparing batteries by Ah alone is misleading: a 100 Ah 12 V battery holds 1.2 kWh but a 100 Ah 48 V bank holds 4.8 kWh. Convert everything to kWh before comparing systems.

Is the full nameplate kWh actually usable?

No. Usable energy depends on the recommended depth of discharge and conversion losses. Lead-acid batteries are commonly cycled to around 50 percent of capacity to protect their lifespan, while LiFePO4 is often cycled to 80 to 90 percent. Inverter and charging losses reduce the delivered figure further, so size a bank with that headroom in mind.

What voltage should I enter for a lithium battery?

Use the nominal voltage: 3.7 V for a standard Li-ion cell, 3.2 V for a LiFePO4 cell, and the cell count times the cell voltage for a pack. A 16S LiFePO4 rack is nominally 51.2 V, a 13S Li-ion pack is about 48.1 V. The voltage dropdown above the field covers the common cases.

How do I convert kWh back to Ah?

Rearrange the same formula: Ah = kWh x 1000 / V. If you need 10 kWh of storage on a 48 V system, that is 10 x 1000 / 48, which is about 208 Ah. Remember to add headroom for depth of discharge and inverter losses before choosing the battery size.

Related calculators

The conversions that procurement and engineering use alongside this one.

Ah to kWh Battery Converter | UK Calculator | Purely Energy