If you have a smart meter you can figure this out from your Usage Patterns chart in your desktop account. Get there by selecting ‘Usage’ then ‘Usage Patterns’.
If you were looking for changes you could make at home to become more power efficient, you would check your Usage Patterns chart to see when your highest usage tends to be.
Let’s say this is between 5.30 and 7.30 in the evening.
You would think about what you regularly do at this time and might realise this is when you’d normally run the bath and have the heater on.
Over the next few days you could experiment with alternating between only having a bath and only having the heater on, to see how it affects your usage during that period.
If your usage falls dramatically when you only have a bath, you know that your heater is using a large chunk of your power. And so you may decide to look into more energy efficient heaters.
If not having a bath makes the biggest difference, you may decide to swap to showers to trim your usage down.