Cooking is via gas, so unaltered.
I log gas, electric and water consumption every week, on a Sunday. The boiler failed mid- week, so this is the first full week with no boiler. In the previous two full weeks with boiler in operation, total gas consumption was £14 per week. In the this full week of no boiler use consumption was £7 - so about half the cost if we put up with one room heated, versus the whole house being comfortably warm.