Key terms:

K = kilo (1000)

W = watt (how energy is measured)

H = hours

If you’ve looked at your energy bill and are seeing kW or kWh, what you’re looking at is the way your energy usage is measured. We’ve created this quick guide to kw and kwh to help you better understand how energy is used and what you can do about lowering energy costs. 

What is kW (Kilowatt)?

A kilowatt (kW) is a measure of power, which represents the rate at which electricity is used or generated. 

What is kWh (Kilowatt-Hour)?

A kilowatt-hour (kWh) is a measure of energy, which represents the total amount of electricity used or produced over time. It tells you how much power is consumed or generated within a certain period.

A quick example:

A 2 kW heater uses 2 kilowatts of power at any given moment.

If the 2 kW heater runs for 3 hours, it will consume 2 kW × 3 hours = 6 kWh of energy.

So how does solar energy work with kW and kWh?

In the context of solar panels, kW measures the capacity of your solar system—the maximum amount of power it can produce at any given moment.

For example, if you install a 5 kW solar system, it means the panels can generate up to 5,000 watts (or 5 kW) of power under ideal sunlight conditions.

If that  5 kW solar system operates at full capacity for one hour, it will produce 5 kWh of electricity. If it runs for five hours, it will generate 25 kWh (5 kW × 5 hours = 25 kWh).

Estimating Your Solar Needs

To size your solar system correctly, you need to look at your electricity bill and determine how many kWh your home consumes each month. If your home uses 900 kWh per month, and your location receives about 5 peak sun hours per day, you can estimate your system size:

900 kWh ÷ (5 sun hours × 30 days) = 6 kW system

This means you’d need a 6 kW solar system to generate enough electricity to cover your monthly usage.

An important factor to consider though is when you are using your energy at home. If you are out during the day, with only a few appliances running (like your fridge) and you use your energy to cook, watch tv, or run the aircon in the evening or nighttime when your solar panels aren’t producing energy, you will be purchasing power directly from the grid, the same as if you didn’t have a solar system.

In this scenario, your extra solar energy produced by your system (kW) not getting used by your household during the day, will be sold back to the grid as a feed-in tariff. This money will then be able to offset your energy consumption during the night.

Another method of storing your unused solar energy (kWs) would be to purchase a solar battery. With a battery, excess kW are stored for later use when your solar system isn’t generating any power, aka during the nighttime or a blackout.

Summary

When choosing a solar system, you need to consider both kW and kWh:

• Solar Panel Capacity (kW): The size of your solar system is measured in kW. A higher kW system means more power generated for your home.
• Energy Production (kWh): Your system’s actual energy production depends on factors like sunlight hours, panel efficiency, shading, and weather conditions. The more kWh your system generates, the more electricity you can use or store or sell back to the grid.

Understanding the difference between kW and kWh is crucial when planning a solar energy system. While kW tells you the system’s capacity, kWh measures the actual energy produced. By evaluating your energy consumption and available sunlight, you can determine the right solar system size to meet your needs, ultimately saving on electricity costs

Need some more information about kW and kWh? Our solar experts can provide free solar assessments your home. Get a quote here or call us on 07 4940 2900.