Yes, immersion heaters can use a lot of electricity because they rely on electric resistance heating, which is less efficient and more expensive compared to gas-powered heating systems.
It is cheaper to only put it on when needed. The reason for this is that the amount of electricity required to heat the water depends on how quickly the heat leaves the tank. Some will leave whenever you use the water, but some also leaves by getting out through the insulation.
Immersion heaters will typically tend to use around three kilowatts of electricity per hour, leading to average running costs of 50p per hour.
Heating water using electricity is more expensive than heating water with gas. A typical immersion heater uses three kilowatts of electricity an hour, so it will cost the average house about 50p an hour to run.
The off-peak immersion will automatically use cheaper electricity over night to heat the water. The on-peak immersion can be used anytime but should only be turned on during the day to re-heat the water if the store of water has been exhausted.
The main disadvantage of an immersion heater is that you can't use it to heat a small amount of water. Each time you need hot water, you have to wait until all the water in the storage tank has been heated to the desired temperature. This is a time-consuming process and one that will unnecessarily waste electricity.
If you are using an immersion heater that is well insulated (which you should be), then it can keep water hot for several hours. Using one with a thermostat will save you money, as you can control the desired temperature and shut the heater off once it reaches this.
Immersion heaters use electricity to heat water, but their main disadvantage is that they cannot heat small amounts of water, which makes heating a tank of water lengthy. It typically takes an immersion heater 2–3 hours to heat the water, making it time-consuming.
A simple immersion heater should heat water with nearly 100% efficiency.
Typical running costs for your immersion heater
Heating one full cylinder (normally 120 litres) will cost about €1.30 per day. Actual usage costs will vary depending on cylinder size and the demand for hot water. It takes about 2.5 hours to fully heat 120 litres from cold.
The main benefit of keeping an immersion heater is as a backup supply of hot water. Immersion heaters have their own electricity supply and don't rely on the boiler. So if your boiler breaks down you will still have access to hot water.
It's generally much cheaper to heat water using your central heating system, rather than using electricity with an immersion. The exception might be during the summer, when you have your central heating turned off, or if you have an old inefficient boiler.
If you have a 2100W (2.1 kW) washing machine and you run it for an hour, it'll use 2.1kWh of electricity in that hour. If electricity costs 34p per unit, multiply 2.1kWh by 34p and you get a grand total of 71p.
Some estimates state that turning your water heater off at night could save you up to 10% on your monthly energy bills. If you have an electric water heater, and you're on an Economy 7 tariff, then it's usually more cost-effective for it to turn on for at least a couple of hours during the night.
All direct water heaters whether they are unvented, thermal store or combination tanks have immersion heaters. An immersion heater may last for between two and three years before it burns out and needs to be changed. This time frame does vary between makes and models of water heater.
Although it takes longer and requires more fuel to heat cold water, the energy required to maintain this constant temperature is much more expensive than the few times it is heated when necessary on occasion, due to its non-use, this water is also wasted, as a result, running a boiler continuously consumes more fuel ...
Immersion heaters will typically tend to use around three kilowatts of electricity per hour, leading to average running costs of 50p per hour.
The main reason for using an immersion heater timer is to save energy and reduce your electricity bills. Immersion heaters are powerful appliances that consume a lot of energy, and they can be costly to run if they are left on all the time.
Saving money with immersion heaters
Make sure your immersion heaters are only on when you need them. If your main immersion heater has a timer: make sure the heater is set to timer mode. check that it's set to come on during off-peak times.
If you leave the immersion on, the thermostat will constantly be turning on and off, leading to one of two problems: The immersion could burn out and stop working completely. Boiling water from the immersion cylinder will be pushed into the main water cylinder, resulting in boiling water coming from your cold taps.
It's better to leave the hot water heater on all the time, rather than turning it on and off. This is a very common energy saving myth. But in fact, you really don't need to be heating your water all the time. Your immersion heater or boiler will heat up hot water which is stored in a tank.
Lightly coat the o-ring washer and the face and threads on the tank and immersion heater with silicone grease. The control thermostat on the immersion heater is pre-set to cut out when the water temperature reaches 60°C. This is ample for domestic use.
Many homeowners ask us if they should turn off their water heater between uses to save money. Our professional answer after crunching the numbers? No, unless you're going on vacation for a month or longer, you shouldn't turn off your water heater.