Whats taking up all our electric money?

A few weeks ago I took a 2 week holiday, whilst my family stayed. A week after I came back, my mum told me that whilst I was away, the electric bill (we use the key-meter system, sort of like pay as you go ) was about £10 for one week. Since Id been back its jumped up to £15 each week, the extra £5 being blamed on me.
My days consist of being on my own-built Pc or playing guitar, so of course my Pc is being blamed. Its only got a 500 watt Psu, which is a tiny amount compared to most high-end computers. I do use a widescreen telly as a monitor along with a normal dell monitor, simultaneously. Although that at first was what I guessed to be the problem, I find it difficult to imagine that out of all the other electronics going on in the home (basic electronic utilities, not forgetting another pc), that my pc/telly can take up a whole 33% of our total usage.
Basically, what on earth is the real problem?

Biggest drain is Heating water washing machine tumble drier and so on and as electricity is so expensive £5 is not a lot to use on the basic things as well.

Intelligent Electric Lock : DigInfo

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