storage heaters?

You need to do the maths...

Find out the total rating of the heater(s) in Kilo Watts (kW) - it should be on a plate somewhere on the heater.

Them multiply this by the number of hours the heaters have power during a week.

The answer will be in Killowatt Hours (kWh) then multiply this by the cost of each kWh unit.

I do not have storage heaters but in the UK they're usually connected to a special low rate economy supply as far as I know...

http://en.wikipedia.org/wiki/Economy_7

Standard cost of a kWh varies around the 7p mark

The cheaper economy 7 cost can be as low as 2.3p per kWh but has recently gone up to double this in some areas.

Peccavi
November 2010