We have a new member of the household. It's small, perfectly formed and proving to be a dominant personality. We've all taken to staring at it transfixed, the children rush to please it and we're a bit shocked about what it's telling us.

It's a Wattson. Probably the most fashionable (and more expensive) version of a new trend - measuring your electricity use. You can get free versions from your electricity supplier in many areas, and you can buy cheaper versions. They work by clipping to the cable that comes out of your meter and then if wireless send a readout to the display in your home. We went for the Wattson because it looks rather nice (my reason) and it has accompanying software that is Mac compatible allowing you to carry out detailed long range analysis of your electricity usage (Tom's reason).



Actually I've been waiting just over a month for this little beggar and when it did arrive, the transmitter was faulty. But luckily DIYKyoto responded very quickly and I had a new transmitter within two days. I think they are a victim of success as they are currently having trouble keeping up with orders. And having plugged Wattson in, I can see why.

There is a very simple readout. As you can see we currently have ours in £s. Or when two ovens are going £££££££££s. You can have it in watts too, but we thought £s would concentrate the mind. The figure shown is how much you would pay for electricity in a year, at the current levels of use. There is also a system of lights - blue for lower use, purple for average and red for high. This makes it very easy for the children to understand and has led to them rushing off to turn their bedroom light off just to see the numbers go down and the light change.

Things I've learnt since it arrived. Lights don't use much, except small halogens. My computer uses not much and a lot less than the television. The oven uses stratopheric levels. And turning on the central heating as we did this weekend (more on that later), uses quite a lot of electricity even though it's oil we're burning. Presumably that's the pump to send the water around the radiators but it is something I hadn't taken into account when deciding to go without central heating most of the time.

The idea is that by measuring and understanding our use of electricity, we can modify our behaviour. Understand your behaviour and you can gain control over it. There's more on this in this Do lecture by Matt Jones and Russell Davies, and in particular they mention a project in Finland where the whole city could see how much energy they were using and see how what they were doing affected the light display.