We are not aware of a simple formula that makes the comparison you are looking for. It appears that you need to calculate the cost of gas for your usage requirements. A good plumber will be able to advise the size of boiler and amount of gas you will use for your property. You should consider either a combi or condensing boiler. You can then compare this to your existing oil costs. Gas tariffs can be obtained from supplier’s websites or from the results page on Moneysupermarket.com utilities comparison service. Once you know your gas usage requirements and costs you can also review your use of economy 7 at night.

Question for Paul Schofield

Can you supply formulae to compare electricity, gas and oil prices. We use oil for central & water heating during the day and economy 7 to heat water at night. It would be useful to know if this is the most economical. Also would it be worth considering changing to gas (alowing for pipe installation costs and new boiler? Payback time?

George Steele of Ravensbourne Heating supply a very good booklet "Beginners Guide to Central Heating" In it are some factors to use. However they are somewhat outdated using therms for gas.

Do you know of an up to date version please?

Esor