Gas or electric to heat water

zilthil

I have a pretty old Baxi boiler, probably 25 years old and it heats my radiators and hot water on an old Danfoss timer. It's set to come on at 5am and off at 7am, then on again at 5pm and off at 10pm. The timer has a switch for hot water and one for heating, so you can turn one or both on or off. The tank in the airing cupboard is one of those that has two sections, for rads and hot tap water.

The radiators are needed for the morning, but i have two wood burners downstairs and in the evening they provide enough heat for the thermostat to turn the radiators (gas) off.

A sparky friend has said i would save money if i turn the hot water switch on the timer (gas) off, and put a timer switch on the immersion on the boiler and just have it set to come on for an hour in the morning and an hour in the evening.

I have not experimented with this and don'y know how much energy is consumed in those times for gas or electricity, but if anyone has a rough idea of which is the cheapest way to operate - please let me know. A new energy efficient combi-boiler is just not an option right now, unfortunately.

I suppose what i want to know is, if the gas boiler is heating up the radiator water, does it require more energy (£) to also heat the hot water at the same time, or would it be cheaper to use the immersion?

HappyMJ

In the winter it's always cheaper to use the Gas. In summer it's different for everyone. You may only use the primary units on the gas costing 7p and may also have E7 electricity costing 5p per unit so it would be cheaper using electricity but that is not always the case. You may use enough gas when cooking to be able to use secondary units to heat water. You may also be on a standing charge tariff so it doesn't make any difference or may be on Npower seasonal pricing tariff when again it hardly makes any difference as they charge a higher rate in winter on more units.

Gas requires more energy to heat the water (up to twice) but the cost of that energy is cheaper (maybe a third) than the cost of the electric energy needed.

So more information is needed.

Efficiency of boiler?
Cost of gas primary units and secondary units?
Cost of electricity primary day units, secondary day units and night units (if any)?
And the summer usage and winter usage that you currently use and the tariff that you are on. How many primary units can be used before the unit rate drops to the secondary rate? Standing charge or not?

macman

The same amount of energy is required to heat the water from one fixed temp to another, regardless of what fuel is used.
Gas is around 3p per kWH, electricity on standard tariff is around 10p per kWh. So more than 3 times more expensive, The greater efficiency of electric heating does not offset the much higher unit cost.

HappyMJ

macman wrote: »

The same amount of energy is required to heat the water from one fixed temp to another, regardless of what fuel is used.
Gas is around 3p per kWH, electricity on standard tariff is around 10p per kWh. So more than 3 times more expensive, The greater efficiency of electric heating does not offset the much higher unit cost.

My gas is 8.296p per kWh (for up to 4,572kWh per year which I do not exceed) but even if I did it 2.971p per kWh the seasonal efficiency of the boiler is 50% at heating the water and my E7 electricity is 4.87p per kWh. That's why I use electricity for heating water. It's much cheaper but it doesn't work for everyone.

macman

Yes, which is why I said electricity on standard tariff is 10p. The majority of those on an E7 tariff will not have a gas supply, so the issue would not arise.