Some extra notes on top of what everyone else has mentioned.

I think it depends on your company, but my company has variable rates depending on time and season. Night time is cheaper than during the day. Winter has highest rates, then summer, then spring/autumn. So not only do I use more electricity in winter because it's cold, but the price per Kw increases too...

Also, my company bills at a rate of xxyen per Kw per 10 watts, in addition to the base surcharge. So if I look at my bill there is the base surcharge + the Kw I used X 3 because my house uses 30 watts. I was confused for the longest time because it always looked like they were over charging me, but it's because I didn't realise they triple the bill because of the wattage. I'm not sure if wattage is something that can be changed though, but 30 watts seems to be normal.

And, one last thing to consider, when comparing to others, is if your house uses gas or electricity for water heating, cooking, and heating. My house uses gas for both water and cooking, and I don't use my aircon for heating much, so my ELECTRICITY bill is always cheaper than friends in houses with IH cooking tops and/or electric water heaters/room heaters. Also, I don't own a TV, or use a PC (just a laptop), whereas most friends have TVs running a lot.