Can I ask a really stupid question...

[ELF1981]

I keep seeing the adverts saying that if you wash at 30 not 40 then you can help save the environment... but why is it the temperature rather that the amount of washing done that makes a difference?

energy (either gas or electricity) used to heat the water

I think cos it saves energy in heating up the water.

I'm sure less washing would make a difference too (have to try and get that through to ds )

LOL. Keep seeing the Ariel advert and wondering - I wonder how much engery it takes to heat that extra 10 degrees?

33% more?

[racks brain]

doesn't it take 1 calorie to heat 1g of water 1 degree?

(and if the water starts at room temp ie 20ish degrees it'll take twice as much energy to heat it to 40 as to 30)