Watt-Hours to Amp-Hours: The Conversion, in Plain English

The formula, both directions

Ah → Wh: multiply by volts

100Ah × 12V = 1,200Wh
100Ah × 24V = 2,400Wh
280Ah × 12V = 3,360Wh

Wh → Ah: divide by volts

1,024Wh ÷ 12V = ~85Ah
2,048Wh ÷ 24V = ~85Ah

That last pair is worth sitting with. Two batteries, both "85Ah", one holding double the energy of the other.

Why amp-hours is used to flatter batteries

Amp-hours measures charge, not energy. On its own it's incomplete.

It survived because 12V systems used to be universal — in a world where everything is 12V, comparing amp-hours is fair. Once voltages vary, it stops meaning anything.

The number that actually matters: usable energy

Rated capacity is not what you get. Two separate discounts apply.

1. Depth of discharge

LiFePO4 — you can use most of it, routinely, without harm.

Lead-acid — you should only take it down about halfway. Go deeper regularly and you kill it fast.

So a 100Ah lead-acid battery advertising 1,200Wh realistically gives you about 600Wh. That's not a trick — it's just how the chemistry works, and it halves the honest comparison.

2. Inverter losses

Turning battery DC into household AC costs you roughly 15% as heat. verify

So a 1,000Wh LiFePO4 pack delivers around 850Wh to your appliances.

Putting it together

The lead-acid battery with the biggest headline number delivers the least.

Why power stations quote watt-hours

Partly honesty, partly convenience.

They run various internal voltages, so amp-hours would be meaningless across brands. Watt-hours is directly comparable — and it's the unit you need anyway, because appliances are rated in watts.

Every runtime on this site is worked out from watt-hours for exactly that reason.

Conversion table

The numbers you are most likely to be looking up, at the three voltages that actually appear on batteries.

And the other direction, for the capacities power stations are actually sold at:

Worked examples

"Is a 100Ah lithium battery bigger than my 1,000Wh power station?"

At 12V, 100Ah is 1,200Wh. So yes, slightly — on paper. In practice they are close, and the power station includes an inverter, outlets and a charger, while the bare battery does not.

"I have a 200Ah lead-acid bank. How does that compare to a 2,000Wh unit?"

200Ah × 12V = 2,400Wh rated. But lead-acid should only be drained about halfway, so your usable figure is nearer 1,200Wh — meaningfully less than the 2,000Wh unit, despite the larger headline number. This is the single most common way people overestimate a battery bank.

"My solar controller is rated 30A at 12V. What can it deliver?"

30A × 12V = 360W. If you connect 400W of panels, the controller is your ceiling, not the panels.

"An appliance says 5A at 120V. What does that cost me?"

5A × 120V = 600W. Run it for two hours and you have used 1,200Wh — more than a 1,000Wh power station holds. Appliance labels frequently give amps rather than watts, and this is how you translate them.

Why this matters when you are shopping

Two places where getting this wrong costs real money.

Comparing a DIY battery bank to a power station. Bank listings quote Ah, power stations quote Wh, and the comparison is meaningless until you convert. Add the lead-acid depth-of-discharge penalty and a "bigger" bank is often smaller.

Reading RV and marine specs. That whole world speaks Ah. If you are deciding whether a power station can replace a house battery, converting is the only way to compare like with like — and remember the power station also brings the inverter that the house battery needs separately.

The short version

Multiply amp-hours by volts. That's it.

Then remember that rated capacity isn't usable capacity — take off the inverter loss, and for lead-acid, half the battery on top of that.

Do that and the comparisons stop being confusing, and a few "bargains" stop looking like bargains.

If what you actually want is to know how long something will run rather than how big the battery is, watt-hours explained covers that, and the sizing calculator does the arithmetic for your specific appliances.