how much does it cost to run my 800Watt heater for 2 hours?

[24jasmine]

[Buenchico]

The easy bit first:
Your heater is rated at 800W = 0.8kW. You're using it for 2 hours, so that's 1.6kWh ('kilowatt hours' = 'units').

Now things get more complicated:
There are many suppliers of electricity. Each of them has different tariffs. Further, there's not just one tariff for each supplier. There are regional differences, plus schemes for light users, day/night tariffs (e.g. 'Economy 7') etc. So, altogether, there are several hundred different tariffs across the country. Without knowing which one you're on, it's impossible to give a precise answer.

However, the tariff I'm on charges about 14p per unit for the first few units used in each quarter, then about 8p per unit thereafter. If we assume:
(i) that you're on a similar tariff to me; and
(ii) that your regular usage of electricity has already taken you beyond the point where the higher rate applies ;
then you'll be paying about 1.6 x 8p = about 13p.

Chris