Central Heating or Immersion Heater
It is usually cheaper to heat your hot water using your boiler if you have one. However if you are on an Economy 7 tariff it is cheaper to heat up the water overnight, during those economy hours. Using an immersion heater is the most expensive way of heating water and it’s especially expensive during the day if you are on an Economy 7 tariff, because while the electricity is cheaper during the night the daytime tariff is usually higher than normal.
Combi Boiler or Regular Boiler?
If you have a larger family then you will find that a regular boiler with a hot water storage tank is most cost effective, however if you have a smaller household, using less hot water, then a Combi Boiler is likely to be the most efficient (and cheapest) system for you. A combination boiler (Combi) heats water on demand rather than having a storage tank. If you are thinking of changing your boiler you may be eligible to take advantage of the Governments Green Deal Programme, read more here.
Water Heating with Economy 7
If you are on an economy 7 tariff your hot water system should be set to automatically turn on when the electricity is at its cheapest rate. You should make sure your tank is really well insulated so that the water stays as hot as possible for as long as possible.
Correct Use of Your Immersion Heater
If you run out of hot water during the day/evening you may need to put on the immersion heater, which is sometimes called a boost. To make this as economical as possible, you should run this for as little time as possible to get the hot water you need.
Immersion Heater – Mythbusters
You may have heard some people say that it is cheaper to leave the immersion on all the time rather than turn it on and off again. However, this is not really true. The immersion heater is usually positioned towards the top of the tank so that when it is turned on it heats the top layer of water in the tank. This means you quickly get a quantity of hot water that will be enough to wash up, bath the kids or have a shower. Once you have done that you can turn off the immersion heater and allow the normal water heating to commence on the next economy cycle.
If you leave the boost heater on then the convection current in the tank will start to allow the whole tank to be heated by the immersion, and because you will be using the higher rate electricity this will get expensive over time.
We did have an opportunity to try this out when the Economy 7 heater in our hot water tank broke a few months ago so, in the interests of DIY Doctor research, we did a controlled experiment for a couple of days and measured the amount of energy used and the relative price of the units used. Our findings agreed with the Energy Saving Trust’s recommendations.