# Get a rough idea of power consumption in a heater

I have a 2.5Kw ceramic fan heater which recently appears to be outputting less heat than it did when it was new.

My theory is that there are 2 separate heating elements because there are 2 heat levels - and I think one of them has failed. Obviously, if I'm right, it will be consuming less power than 2.5Kw on full output.

I don't own a power meter and my home power usage is too erratic to use the main house reading to tell the difference between 1.25Kw and 2.5Kw.

How can I tell the power usage of this heater to be reasonably sure whether it is running 1 element or two?

• What voltage is your country on, and do you have resettable fuses - if so, what values are most of them? (I'm thinking along the lines of - as a one off - heavily loading a circuit so that the extra current if a second element will trip the fuse) Jan 20, 2021 at 6:05
• @davidgo Creative suggestion! I'm in UK on 240v; I do have circuit-breakers so this might be viable. Slightly more problematic than I would like, but may be my best option. Thank you! Jan 20, 2021 at 17:32
• do you know the math required to work out the loading? If not let me know the current rating of the circuit breaker you want to use for the task. (The closer to 10 or 15 amp the better!) Jan 20, 2021 at 18:51

Run the heater on the lower heat setting and allow time for its output to stabilise.

Move one hand cautiously towards the hot air stream, taking care not to move it too close to the heater, and do not touch the heater.

Switch the heater to the high setting with your other hand. If the element is working, you should be able to feel the additional heat within a few seconds, and move your hand away immediately when you do.

Caution: do not leave the heater unattended, do not touch the heater (apart from its switch), do not move your hand into the hottest part of the air stream.

Method 2:

Let someone else be looking at the meter when you turn the second element on and then off. If they see a sudden change in power use at that moment, then the element is working.

Repeat several times to be sure. The amount of power used is much larger than lights, frig, freezer, TV etc. usage so it should be easy to tell it apart from general fluctuation in power demand from the house. It is comparable to an electric oven or kettle, and you can get an idea by turning the first element on and off.

• Essentially, method 1) is what I've already done and makes me think there is a problem. I'm pretty sure it was impossible to hold your hand directly in front of it on full power, and now I can. There is no obvious difference between the 2 settings. I'm just trying to verify that by seeing if I can find the power consumption. Jan 19, 2021 at 12:42

If you are on 240V fit a 5amp fuse to the plug. This should blow at 2.5kW but not at 1.25kW. (or get a power meter - they are quite cheap and quite handy)

• Note that it won't blow instantly at only double the rated current. You might need to wait a couple of minutes. It's apparently possible to borrow power meters in some places Apr 1, 2021 at 14:06

An alternative to method 2 in the answer by @WeatherVane

If you have a smart meter for your electricity supply, you can monitor the power usage using the smart meter monitor.

The monitor in the image below, as you can see is reading 321 watts when the correct screen is selected.

You can see what electricity is being drawn at any time using these monitors. Just look at the power draw before and after switching the heating on. If the power draw is 2.5KW more when switching on, you know your heater is working as it should.