h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

I'm probably over-thinking this, but I'm trying to work out what uses more electricity over an average month. My 500 Watt oil heater which I've set low-enough so that it tends to cycle on for around 3 minutes in every 10; so it only uses 500Watt for around a third of the time. Or an 80w tube wall heater thing which, although thermostatic, is designed to stay on all the time; therefore using a constant 80W at all times.
How do I calculate this ? ?

The simplest thing to do is get one of those electricity usage monitors you plug in to an outlet.

http://www.amazon.co.uk/Power-Monitors/b?ie=UTF8&node=1938287031

I've got one I bought a few years ago, but it's completely useless now simply because I have absolutely no idea where I stored it.

Something that uses 500 watts a third of the time would be on for 10 days out of the thirty that are in a month. So, 10 X 500 is 5,000.

80 constantly would be 80 X 30, which equals 2,400. I think that would use only half as much power as the first one.

One of those power monitors can be quite handy. Didja know the LED clock on your microwave oven uses more electricity than the magnetron inside it?

Look around your home and notice how many things are never really turned off, how many glowing LEDs and LCD displays you see in a "dark" room.

True.

I see glowing displays from my two carbon monoxide detectors, the "on" button for my computer monitor, the display on my modem, my stereo, my audio system that's hooked up to my computer, and the gadgets that make mouse-repelling noises.

Thanks! That makes sense. I knew I was over-thinking it