When you're exploring solar and battery options, you'll often see the terms kW and kWh. These stand for kilowatt and kilowatt-hour, which are units of measurement used to describe electricity. Put simply, kW is how fast electricity is used or generated, while kWh is how much electricity is used over time.
What is a kilowatt (kW)?
A kW is a measure of power and tells you how much electricity something can produce or use at a given moment in time.
Solar systems are rated in kW. This reflects the maximum power they can generate under ideal conditions, such as when the sun is shining at its brightest during the day.
For example, a 6.6kW solar system can generate up to 6.6kW of power under ideal conditions, but its actual power output will vary throughout the day depending on the sunlight intensity.
What is a kilowatt-hour (kWh)?
A kWh is a measure of energy and tells you how much electricity is used or stored over time, like the amount of water collected in a bucket.
You’ll see this measurement on your electricity bill, where you’re charged based on how many kWh of electricity you’ve consumed. It’s also the same unit used to measure how much energy your solar system generates or how much energy a battery can store. For example: If you run a 2kW heater for 3 hours, you’ve used 6kWh of energy.
When are kW and kWh used in reference to solar and battery systems?
When it comes to solar and batteries, kW and kWh describe different but related things.
Solar systems
Your solar system size is measured in kW. This tells you how much power the system can produce at one moment under ideal conditions.
Solar energy production is measured in kWh. This tells you how much electricity the system generates over time, such as across a day, month or year. A larger kW solar system can produce more power at once, but the total energy it generates (kWh) will still depend on things like sunlight hours, roof orientation, shading and the time of year.
Batteries
Batteries are often described using both kW and kWh, because each tells you something different.
Battery capacity (kWh) refers to how much energy the battery can store and use later, while the battery output or charging speed (kW) tells you how much electricity the battery can deliver at one time and how quickly it can charge or discharge.
Both matter when choosing a battery. One tells you how long it can provide energy, and the other tells you how much it can supply at once.
Battery energy example
Imagine a battery that stores 10 kWh of energy. If you’re using it to run appliances that use about 2kW at the time, it could last for about five hours.
If it’s running appliances that use about 5kW, it could last for around two hours.
The higher the power draw (kW), the faster the stored energy (kWh) is used.
Check your appliances or appliance manuals to find out how much power they use.
Get solar package recommendations with Kleenheat Spark
Understanding kW and kWh can make it easier to compare solar and battery options, but the right setup will depend on your home and household’s energy use.
When you request a recommendation through Kleenheat Spark, we use your electricity usage and household details to recommend solar and battery packages sized to suit your needs, so you can feel confident choosing an option that makes sense for you.