You'll see both on your electricity bill and in every solar quote. Understanding the difference helps you size a system and read your bills with confidence.
You've probably seen kW and kWh on your electricity bills, online or on TV, but do you know what they mean, or how they differ? Let's clear it up.
First, the basics:
- k stands for kilo, or "one thousand".
- W stands for watt, a unit of power.
- h stands for hour, a measure of time.
kW vs kWh
kW (kilowatt) is 1,000 watts, a measure of power, or the rate at which electricity flows. The more watts an appliance needs, the more electricity it draws. A 100W bulb shines brighter than a 20W one, but uses more power to do it.
kWh (kilowatt-hour) measures energy, power used over time (kW × hours). Run that 100W bulb for one hour and you use 0.1kWh. Run a 1kW washing machine for one hour and you use 1kWh; for two hours, 2kWh.
Why the difference matters
1. Sizing the right solar system
A solar system's size is described by its peak power in kW, a 5kW system can produce up to 5kW on a bright, sunny day. To choose the right size, you also need to know how much energy (kWh) you use on an average day, along with your roof orientation, location, savings goals and future plans like buying an EV. A free in-home assessment ties all of that together.
2. Understanding your bills
Electricity retailers charge per kWh, so knowing the difference helps you track your usage and spot which appliances cost the most to run.
You can take this further with a Solahart Home Energy Management System (HEMS), which:
- brings your connected appliances and energy devices under one platform,
- predicts solar generation using seasonal and daily weather patterns to help you time high-energy tasks, and
- lets you view your energy data anytime through the atHome app.
If you're thinking about going solar, get in touch for a free in-home assessment to find the right-sized system for your home.