Watt-Hours vs Amp-Hours: Real Capacity

Why watt-hours matter more than amp-hours

When you compare portable power stations, the capacity figure in the title is usually given in watt-hours (Wh). That is the number to use when comparing models, because it tells you the total energy the station can store. Amp-hours (Ah) tell you only the charge, not how much energy that charge represents. The missing piece is voltage.

Electricity is measured in watts, a unit of power, as the U.S. Energy Information Administration explains. A watt-hour is one watt of power used for one hour. Amp-hours are a measure of charge: one amp flowing for one hour. To get watt-hours, you multiply volts by amp-hours. Two stations with the same amp-hour rating can hold very different amounts of energy if they run at different voltages.

On a power station listing, the watt-hour figure is the one that lets you compare a small camping unit with a larger home backup model. Amp-hours alone do not tell you how long a device will run, because the station's voltage changes the math. This is why the guides on this site compare stations on stated watt-hours, not amp-hours. For example, see the best portable power station guide.

• Watt-hours = volts × amp-hours
• Watt-hours measure total energy; amp-hours measure charge
• Voltage varies between stations, so amp-hours alone are not comparable

How to read amp-hours on a listing

Some listings show amp-hours (Ah) alongside watt-hours, often as part of the battery specification. A figure like "10Ah" tells you the charge capacity, but without the voltage you cannot know the energy. If the listing also states the voltage, you can multiply the two to get watt-hours. If it does not, the amp-hour figure is not useful for comparison.

When a listing gives both figures, check that they are consistent. For example, a station with a 12V battery and 100Ah would have 1,200Wh. A station with a 48V battery and 25Ah would also have 1,200Wh. The watt-hour figure is the same, but the amp-hour numbers look very different. This is why the watt-hour figure is the common language for comparing capacity.

On this site, the buying guides list capacity in watt-hours because that is the figure that makes sense across different brands and models. If a listing only shows amp-hours, look for the voltage in the full specifications or on the maker's page before you compare it with another station. For camping-specific advice, see the best camping power station guide.

Voltage and capacity: why the same Ah can differ

Portable power stations use different internal battery voltages. A small unit might run at a lower voltage, while a larger home backup unit might use a higher one. The same amp-hour rating at a higher voltage means more watt-hours, so more stored energy. This is why amp-hours alone cannot tell you which station holds more power.

The U.S. Energy Information Administration explains that electricity is measured in watts, and a watt-hour is a unit of energy. When you see a listing with both volts and amp-hours, you can multiply them to get watt-hours. But the listing title usually states watt-hours directly, so you rarely need to do the math.

When comparing two stations, use the watt-hour figure from each listing. If one station shows only amp-hours, find the voltage in the full specs or on the maker's page. Then you can convert to watt-hours and compare fairly. This is a simple way to avoid being misled by a high amp-hour number that comes from a low voltage. For home backup needs, check the home backup guide.

What this site cannot say about capacity

This site compares stations on the stated details from listings, including watt-hours and amp-hours. It does not measure actual capacity or runtime. The maker's page is the place to find detailed specifications, such as the exact battery voltage and any notes on usable capacity.

Runtime depends on the power draw of the devices you connect, which is not something this site can predict. The watt-hour figure tells you the total energy, but how long it lasts depends on what you plug in. For that reason, the guides here focus on capacity and output as listing terms, not on runtime promises.

When you read a listing, treat the watt-hour figure as the primary capacity number. If amp-hours appear, use them only with the voltage to confirm the watt-hour total. For any question about how long a specific device will run, check the maker's documentation or contact the maker directly. For solar options, see the solar generator guide.

What to pick for your situation

Questions

What is the difference between watt-hours and amp-hours?

Watt-hours measure total energy, while amp-hours measure charge. To get watt-hours, multiply volts by amp-hours. Since power stations run at different voltages, amp-hours alone do not tell you how much energy a station stores.

Why do power station listings show amp-hours?

Amp-hours are a common battery specification, but they are only meaningful with the voltage. Listings may show amp-hours as part of the battery details, but the watt-hour figure is the one to use for comparing capacity across models.

Can I compare two stations by amp-hours alone?

No. Two stations with the same amp-hour rating can have different watt-hours if they run at different voltages. Always compare watt-hours, or convert amp-hours to watt-hours using the voltage from the listing or the maker's page.

How do I convert amp-hours to watt-hours?

Multiply the amp-hours by the voltage. For example, a 12V battery with 100Ah has 1,200Wh. The listing may state the voltage, or you can find it in the full specifications on the maker's page.

Why does this site use watt-hours instead of amp-hours?

Watt-hours are a common measure of energy that works across different voltages and brands. This site compares stations on stated watt-hours so you can compare models fairly, without the confusion of amp-hours at different voltages.