Ways to measure energy use
| Tool | What it measures | Good for |
|---|---|---|
| Plug-in power meter | Watts now and kWh over time for one plug-in appliance | Fridges, freezers, TVs, heaters, computers |
| Smart plug with energy monitoring | The same, logged in an app | Tracking use over weeks |
| Smart meter data | Whole-home use every 30 minutes | Finding when big loads run and overnight base load |
| Whole-home energy monitor | Real-time use from sensors in the switchboard | Hard-wired loads such as hot water, pool pumps and ovens |
| Energy rating label | Tested kWh a year or input power | Comparing before you buy |
Hard-wired appliances
Hot water systems, ovens, cooktops and ducted air conditioning are wired into the switchboard. Only a licensed electrician should install monitoring sensors there.
How to measure an appliance
Plug the meter in
Put the power meter between the wall socket and the appliance, and reset it.
Leave it for a week
Appliances on thermostats cycle on and off, so a short reading can mislead. A week captures normal use.
Read the kWh
Divide by the number of days to get kWh a day, then multiply by 365 for a year.
Turn kWh into dollars
Multiply by your rate. At the Ausgrid reference rate of 33.14c, 1 kWh a day is about $121 a year.
Then compare with our appliance running cost figures. An old fridge using far more than a new one of the same size may be worth replacing. See replacing old appliances.
Using smart meter data to find hidden loads
Look at your half-hourly data between about 1am and 4am, when most homes are asleep. That is your base load: fridges, routers, standby and anything left on. If it seems high, switch things off one at a time and watch the next night's data. Our reading smart meter data guide explains how to get and read the data.
Questions about measuring energy use
Use a plug-in power meter or a smart plug with energy monitoring for a week, then read the kWh. For hard-wired appliances, use smart meter data or an electrician-installed home energy monitor.
Check your smart meter data between about 1am and 4am. Then switch suspect appliances off one at a time and see which change lowers the overnight reading.
They are accurate enough for household decisions, such as whether an old fridge is worth replacing. Measure over a week for appliances that cycle on and off.
A little, usually under a watt or two, to stay connected to wi-fi. It is small, but it means a smart plug left on every device adds a bit of standby of its own.
Hardware and electronics stores sell plug-in power meters, and some local councils and libraries lend them for free. Check with your local library.
Sources
Every rate on this page comes from the regulator or the regulated retailer. Last checked October 2026. Prices include GST unless we say otherwise.