Generator kVA vs kW: Understand the Two Ratings

What kVA and kW mean on a generator listing

A generator listing can state power in watts or in two larger units: kW and kVA. The abbreviation kW stands for kilowatt, or 1,000 watts. Watts are the unit used to measure electrical power, as the U.S. Energy Information Administration explains in its pages on measuring electricity. The abbreviation kVA stands for kilovolt-ampere, which measures apparent power in an alternating-current circuit.

In plain terms, kW states the real power, the output that can do work in your appliances. kVA states the apparent power, the voltage multiplied by the current that the generator's alternator can supply. The two figures are equal only when the connected load keeps voltage and current in step. Most household loads do not, so the two readings differ. The ratio between them is the power factor of the connected equipment.

A listing that states only kVA does not directly show the usable watts. A listing that states kW or running watts does. That is why the unit of measure matters when you compare generators for backup power. See generator running vs starting watts for how the watts figures appear in a title.

Why some generator listings show kVA

Portable generator listings on this site usually state running watts and starting watts in the title. Standby generators, larger commercial-style units and some portable models may state kVA instead. The convention comes from how the alternator is rated: kVA describes the electrical capacity of the generator head before the power factor of the connected load is applied.

A title that reads a kVA figure is stating apparent power, not the watts available to your appliances. To compare that unit with a generator titled in watts, you would look for the maker's stated running watts or continuous output, usually in the maker's specification page or the owner's manual.

The continuous rating is the figure that describes sustained output; see generator continuous rating. To read the full set of ratings on a unit, see generator nameplate specs.

How kW and kVA relate

In an alternating-current circuit, the generator supplies voltage and current. Apparent power, measured in kVA, is the product of the two. Real power, measured in kW, is the portion of that product that does work in resistive and motor loads. The gap between the two is the power factor of whatever is connected.

For a resistive load, such as a heating element, voltage and current stay in step, and kW and kVA sit close together. For a load with a motor, such as a refrigerator compressor, the current lags behind the voltage, and the apparent power reads higher than the real power. The same generator can show a different kW figure depending on the loads attached.

This site does not publish power factor figures for specific generators. The power factor can appear on the generator's nameplate or in the maker's manual, and a listing may not state it. See generator power factor for more on the term.

What to look for when you compare generators

When comparing generators for hurricane season, look for a stated real-power figure: running watts or continuous output on a portable generator, kW on a standby unit. A kVA figure alone does not give you the usable watts, because the power factor of your appliances decides the relationship.

A listing title may show one figure in watts and another in kVA. The two figures are not interchangeable. The watts figure, when stated, is the one this site reads for the running output. When a listing states kVA but not watts, the missing real-power figure is a detail the seller has not stated.

This site does not size a home or promise that a wattage figure runs specific appliances. Read the appliance label for its stated watts or amps. Wiring and load decisions belong to a licensed electrician, the maker and the local permit office; ask them before you connect anything.

For the difference between starting and running watts, see generator running vs starting watts. For the guide to comparing large portable units, see Best Large Portable Generators for Hurricanes.

The Florida hurricane season context

Hurricane season planning means checking your backup equipment before the season begins. The National Weather Service's before-the-storm checklist includes checking emergency equipment such as flashlights and generators. Each Florida county runs an emergency management program, and the Florida Division of Emergency Management directs residents to their county's office for locally significant information.

Understanding whether a generator is rated in kW or kVA matters when you read a listing and when you compare one model with another. The real-power figure, in watts or kW, is the number that states the generator's usable output. A kVA figure is an alternator rating; it needs the power factor of your appliances to translate into usable watts.

Before the season, keep the owner's manual with the unit and check the maker's stated ratings. The maker's page is the place that resolves what a model's kVA figure means in watts. For the full hurricane shopping picture, see Best Backup Power for Florida.

How this site reads the two ratings

This site's buying guides compare generators on stated details from the listings: running watts, starting watts, fuel type, outlets and features. When a listing states kVA instead of kW or watts, the guide records the missing real-power figure as a detail the seller has not stated.

A generator that appears many times in the guide pool may appear with different stated figures under different listings. The same model may be titled in watts in one listing and in kVA in another. The maker's specification page settles the rating that the listing title leaves unclear.

For homes with room for a permanent unit, see Best Standby Generators for Florida Homes. For a portable mid-size unit, see Best 3000 to 5000 Watt Generators for Hurricanes.

What to pick for your situation

Questions

What does kVA mean on a generator?

kVA stands for kilovolt-ampere. It measures apparent power, the product of voltage and current in an alternating-current circuit. A kVA rating states the alternator's electrical capacity, not directly the watts you can draw from it.

What does kW mean on a generator?

kW stands for kilowatt, or 1,000 watts. It measures real power, the output that can do work in your appliances. When a listing states kW, it gives you a usable output figure in the same terms as running watts.

Which figure should I compare: kW or kVA?

Compare the real-power figure, kW or running watts, when a listing states it. A kVA figure alone depends on the power factor of the connected loads and does not tell you the usable watts.

A listing shows both kVA and kW. What is the difference between the numbers?

The two figures differ by the power factor of the connected load. For a resistive load they sit close together; for a motor load the kVA figure runs higher than the kW figure. The maker's page states the unit's rated figures.

Why do portable generators list watts while standby generators list kVA?

The convention comes from how the alternator is rated. Portable titles on this site usually state running watts, while standby units and some larger units state kVA. Both describe the same generator head from different angles.

Can this site tell me which kVA size I need?

No. This site does not size a home or promise that a rating runs specific appliances. Read the appliance label for its stated watts or amps and ask a licensed electrician to compare the generator's rating with your load.