I’m not sure how many you would a need – a huge number, you might have to have all the walls in your house covered in hamster wheels. That would be a lot of hamsters to look after and a lot of cage cleaning! I’m not sure if gerbils will be any better, I had a hamster and a gerbil when I was little and I think the hamster liked the wheel more, so maybe hamsters would be better 🙂
Well you can work it out. The work done (W) is the force (F) multiplied by the distance travelled (D)
W = F x D
now the force applied is the weight of the hamster. According to answers.com a typical hamster mass is 150 grams, so F = 0.150 x g = 1.5 Newtons.
To get the distance it runs on the wheel we need to know how big the wheel is. I just googled it and 8inches is a typical hamster wheel diameter. So changing this to centimetres and working out the circumference of the wheel you get 64cm = 0.64 metres. Now this is how much it runs for one turn of the wheel. A speed of 1 kilometre per hour is easy for a hamster so lets say it does that for 8 hours straight -> then it will have travelled 8 kilometres (around the wheel 12,500 times!).
Ok, so W = F x D = 1.5 x 8000 = 12,000 Joules which is 0.003 kilowatt*hours. Kilowatt*hours are what are used as “units of electricity” and you might recognise them from electricity bills. The power is the rate of work done and is just 0.4 Watts. So you would need 100 hamsters running together to power a 40 Watt light bulb. To power your house would need a lot more!! Hmmm, I just looked it up and an average UK household with 2 parents and 2 children uses about 20 billion Joules of energy in a year and so requires a power rate of like 600 Watts (this is ON AVERAGE! if you put on the kettle or toaster it uses much more, but also there are times when you don’t use much electricity). 600 Watts at 0.4 Watts per hamster means you need 1500 hamsters. But if they can only do 8-hour shifts you need 4500 hamsters. But lets call it 5000 hamsters for safety! 😉
As for gerbils, it seems they are a bit lighter than hamsters and so cannot apply as much force to their wheels so would not be as good for generating power! 🙂