The Differences Between kVA and kW

Diesel generators come in various sizes and capacities, making it easy to find the perfect model for your home or business. Two terms you’ll encounter regularly when looking for generators are kW and kVA.

Both describe the generator’s power capabilities, but they’re different concepts. Understanding what each means can help you choose the right generator for your business or home.

So, let’s get straight to it and explore the difference between kW and kVA.

What is kW?

Kilowatt (kW) describes the real power of your generator and its ability to support connected loads. For example, if you’re connecting electrical appliances, equipment and lighting, you’ll need a generator that can provide enough power to keep them running.

Put simply, kW refers to the active power of your generator that’s delivered to your electrical system. One kW equates to 1000 watts.

Power in kilowatts is calculated with the following formula:

kW = Voltage (V) X Current (I) X Power Factor (PF)

The power factor measures electrical efficiency and combines the ratio of real power with apparent power. These ratios range from 0 to 1, with higher ratios indicating more efficiency for your electrical systems.

What is kVA?

Kilovolt-ampere (kVA) defines your system’s apparent power, combining kW (actual power) and kVAR (reactive power). Reactive power isn’t vital for your generator’s functionality, but it does maintain consistent voltage levels in the system.

One kVA equates to 1,000 volt-amperes, defining the total force or power within an electrical system, combining reactive and usable energy.

Apparent power is calculated by using the following formula:

kVA = Voltage (V) X Current (I)

As you can see, the kVA calculation doesn’t include a power factor (PF) as it focuses on non-useful and useful components.

What’s the difference between kW and kVA?

Understanding the difference between kW and kVA can be complex, so to make it easier, think of the two like this:

• kW is what your generator actually uses.
• kVA is what the generator uses and how much it needs to power devices.

Once you know the key differences, you can choose a generator that meets your requirements. Let’s explore why they matter.

Generator size

When shopping for diesel generators, sellers usually list them with a kVA power rating, which explains the total power they can supply. While some generators are listed in kW, factoring in kVA ratings ensures the generator can handle connected equipment.

Efficiency and cost

The kW rating defines the generator’s operating costs and efficiency. Generators with high power factors are more efficient as they can use the power for extra work, leading to cost savings over time. Lower power factors can cause losses in your electrical systems, resulting in higher running costs.

Load management

Load management is integral to keeping your generator functional. Knowing the kVA and kW requirements reduces the risks of overloads and electrical current shortages. If you don’t maintain optimal electrical pressure, the generator could fail.

kW into kVA Conversion

When converting kW to kVA, you’ll need to consider the power factor. For example, calculating the kVA of a 5kW generator with a power factor of 0.8 means you need to divide the kW and power factor:

5 divided by 0.8 = 6.25, and that’s the kVA rating of your generator.

How to convert kVA to kW

When converting kVA to kW, you’ll need the generator’s power factor, which you can find in your manual. Then, multiply the power factor and kVA to determine kW. Here’s how it would work with a 10kVA generator and 0.7 power factor:

10 X 0.7 = 7 – the kW rating of your generator.

Why do some diesel generators list kW and others kVA?

When looking for a commercial generator or generator for the home, you’ll notice some models have kVA ratings, and others use kW. Both power ratings are important terms within the generator industry. Let’s take a look at why manufacturers use different terms:

• Regional Differences: In North America, manufacturers often list generators in kW, which means some will continue this into different markets.
• Large-Scale Power Needs: Industrial companies or those with extensive needs are more interested in the system’s apparent power (kVA), which defines the total load a generator can handle.
• Small-Scale Power Needs: Homes and those with Small-Scale needs are more focused on the actual power of a generator, so lower capacity models often use kW ratings.

Even if a generator lists one power rating, the other will probably be included in the specifications, making it easier to find a model that suits your prime and backup power needs.

Need help choosing a generator?

Choosing a generator with a suitable power output gives you peace of mind, but knowing where to start is challenging.

Solent Power is one of the UK’s most reputable generator distributors for all power needs. Please contact our sales team for support today. We also offer a generator installation service, which includes site preparation.