Battery Capacity vs Inverter Power: Read Specs

Two Figures Measure Different Things

A portable power station listing usually shows two headline numbers: a watt-hour (Wh) figure for capacity and a watt (W) figure for output. The two units measure different things, and neither alone tells you what the station can do for a Texas home.

The U.S. Energy Information Administration explains that electricity is measured in units of power called watts, and that one watt is a very small amount of power. A watt-hour is that power held over time: one watt-hour is one watt of power stored or delivered for one hour.

On a listing, the Wh figure describes the battery: the total energy stored inside. The W figure describes the inverter: the most the station can supply at a single moment. The EIA reports that the average U.S. household uses about 10,500 kilowatt-hours per year, which gives a sense of how the units build: a single station's capacity is a small fraction of a home's annual use.

Reading a Listing Title

Listing titles on this site put the two numbers in different orders. A title may list the output in watts first and the capacity in watt-hours second, or the reverse. Read the units, not the position, and look for both figures on the listing page before comparing.

A title that shows only one number gives only part of the picture. A number without a unit is not usable. The listing text and the maker's page should give the full pair.

If a title lists a second W figure such as a surge or peak figure, it is still describing the inverter, not the battery. The battery capacity remains the Wh figure. For more on how the inverter rating and the battery relate, see inverter rating versus battery.

Capacity and Run Time

Capacity in watt-hours is the total stored energy. A station with more Wh holds more energy, so a given load can draw from it longer. The actual run time for a fridge, a router or lights depends on how much those devices draw, which this site does not claim to know for a Texas home.

The maker's manual and the maker's page may show run-time estimates built on a particular load. Read those as the maker's assumptions, not as a promise for the reader's appliances.

This site does not size a home or publish appliance wattage tables. The maker and a licensed electrician decide whether a station matches the appliances a reader wants to power. See run time at half versus full load for why the load changes the answer.

Inverter Power and Surge

The inverter converts the battery's direct current into the alternating current that home devices use. The AC output in watts is the steady limit the inverter can supply. A surge figure, sometimes called peak, is a short burst the inverter can supply when a device starts.

Read the surge figure on the listing and the maker's page. A device that draws more than the steady output at start-up may need a station whose surge rating covers that start, but whether a particular device starts is a question for the maker and an electrician.

For a closer look at the two figures, see continuous versus peak power.

Where to Read the Numbers

Read both figures on the listing, then confirm them on the maker's page and in the manual. A listing may be renamed or combined with a panel or an expansion battery; the stated details are the ones to compare.

If a listing says the station works with an expansion battery, the capacity figure may apply to one unit alone or to a total system. The listing and the maker's page state which.

If a solar panel is included, the capacity and output numbers still describe the battery and the inverter; the panel is a charging input, not an output. The Department of Energy's homeowner's guide to solar is listed in the sources for a general introduction.

For a shopping overview, see the best home backup power stations guide and the mid-size capacity guide.

Prepare Before the Season

Shopping is the first step, and preparing before winter storms or summer heat is part of the same plan. The CDC notes that winter storms can bring cold temperatures and power failures. The Texas Division of Emergency Management and Texas Ready publish preparedness steps for Texas households; both are listed in the sources.

A reader who wants a single overview of backup power options can start with the best backup power for Texas guide, which compares fuel generators, standby units and power stations on stated details.

What to pick for your situation

Questions

What is a watt-hour?

A watt-hour is one watt of power delivered or stored for one hour. It is the unit for a station's battery capacity on a listing. The EIA explains that electricity is measured in units of power called watts and that one watt is a very small amount of power.

What is the inverter power in watts?

The AC output in watts is the most the station's inverter can deliver to a plugged-in device at a single moment. A surge figure, sometimes called peak, is a short burst the inverter can supply at start-up.

Why does a listing show two W figures?

One is the steady AC output and the other is the surge or peak. Both describe the inverter, not the battery. The battery capacity is the Wh figure.

Does a bigger Wh figure mean a longer run time?

A bigger Wh figure means more stored energy, so a given load can draw from it longer. The actual run time depends on the load, which is why this site gives no run times. Read the maker's page for the maker's own estimates.

Which number should I compare first?

Compare both. The Wh figure tells you how much energy the station holds; the W figure tells you what it can supply at a moment. A station that lacks either figure on its listing is hard to compare.