It will take about ½ kWh (half a "unit") to increase the temperature of 10 litres of water by 40ºC. That might be what one person would need to wash up. Just divide what that costs by 10 to find the cost of warming up 1 litre by the same amount to wash hands. You might be paying about 4p per Kwh with gas. That's 2p to wash up and 0.2p to wash hands. To warm 100 litres of water for a bath by the same amount would cost 20p.

No, I dont want to make any alterations like that -and also its impossible to have a gas fire there. I just wanted to know if there was a guidance chart on some internet site thats all. I'm sure that an energy supplier would be able to give some approximate cost for such things. I just wondered if in these days of information that I could find it on a website.

Yes, you'd probably just take out the radiator(s), block the pipes for them and install a gas fire and immersion heater or whatever the options are today (a boiler might not be economical for a studio flat although things are being developed all the time). It's not such a big job and it would mean that you were both just responsible for your own use. It wouldn't be necessary if the flat was being used as a guest room or granny flat but it's something to consider for the long term.

Thanks for taking the time to reply.

No, i dont pay the bills so dont make a profit/loss regarding the gas. The studio flat does have its separate electricity supply and meter but - forgive me if i'm wrong but I dont think its possible to have 2 gas meters because i'd have to have separate boilers and separate gas supplies which would be impossible in this case.

One option to explore is to take a meter reading before and after one bath, one washing up, etc..

I doubt that a gas supplier would want to be tied down to any figures for this as there are too many variables. A bath and a central heating system will certainly use more than would be used in the kitchen though.

Long term, it might be worth investigating separating the supplies and avoiding arguments. It is possible to install "landlord meters" or you could have completely separate supplies. Landlords are not allowed to make a profit from gas or electricity but the separate meters will make billing easier. Few of us tend to be as economical with things if someone else is paying.

No, its not a shared house! Its complicated! Its a shared boiler between 2 units , one a house and one a very small studio flat. I just wondered if there was a website that may give me some clues. I am sure if I phone a gas supplier they will give me the answer. I would personally think that the gas used by a combi-boiler to heat up water supplied to a kitchen tap to wash hands and food would not cost much -but a tenant is arguing with me about this. (There is no bath in the studio flat so I don't need to know what that would cost).

I wonder what your tenants will say if you ask them to pay per bath, per washing up, etc.. A lot depends on how hot the water is, how much water is used, etc.

My guess is that a bath will cost much less than £1 unless someone is really extravagent.

As a landlady of a property with a shared gas bill I would like to know if there is a chart anywhere that shows how much it approximately costs for every type of gas consumption. i.e On a daily basis using a combi-boiler how much does it approximately cost to have a bath? How much does it cost washing pots etc?