Thinking of replacing your immersion heater?
Most people make one key mistake when shopping for a new immersion heater – they pick the first one they come across without understanding what their home really needs. And the issue with that is…
You might end up with a heater that’s the wrong size, is made from an unsuitable material, or is much more expensive to run than it should be. With boiler failures costing UK homeowners around £32.1 million a year, getting the right water heating solution for your home is more important than you might think.
The good news is that choosing an immersion heater replacement doesn’t have to be hard work. Once you know what you’re looking for, it’s a simple job to pick the best one for your home and save yourself money and hassle in the long run.
What will you learn in this guide?
- The types of immersion heaters available, and which is right for your home
- How to work out the correct size based on your hot water cylinder capacity
- The different materials and how it affects performance and running costs
- Should you replace an immersion heater yourself, or hire a professional?
The Different Types of Immersion Heaters
Let’s get one thing straight right from the beginning…
Immersion heaters are not all the same. When you’re browsing your options for a new immersion heater, you’ll typically find three main material options available – copper, incoloy, and titanium. Each material has pros and cons depending on your situation.
Copper immersion heaters are the most common and popular choice by far. They’re inexpensive, efficient, and work just fine in most UK homes. The immersion heater itself typically costs around £20-30 for the element, and then it’s very quick and easy to swap out the old heater for the new one.
However…
If you’re in a hard water area, then you’re likely to find copper immersion heaters struggle over time. Limescale buildup from hard water areas is the enemy of efficiency and longevity with copper heaters.
Incoloy heaters are much better at resisting corrosion and limescale buildup. You’ll pay a little more for one (£30-40 on average), but they should last far longer than copper in hard water areas. Consider them a happy medium between copper and titanium.
Last but not least…
Titanium immersion heaters are the luxury option. They are corrosion and limescale proof, meaning they last for decades if you’re in an area with hard water. They are more expensive, with an element costing around £40-60.
Correct Heater Size Based on Cylinder Capacity
Here’s a question for you…
Have you ever tried putting on shoes that were too small?
Nope, me neither. Most people instinctively know that choosing the wrong size shoes makes them not fit. But when you come to replace an immersion heater, it’s not as obvious. You can end up trying to fit one in your hot water cylinder that just doesn’t work.
Immersion heaters come in multiple sizes, typically ranging from 11 inches all the way up to 27 inches long. Your actual requirement is based on the cylinder capacity in your home:
Small cylinders – up to 120 litres – require an 11-14 inch heater
Medium cylinders – 120-180 litres – suit an 18-21 inch heater
Large cylinders – 180 litres plus – need a 24-27 inch heater
And don’t forget this point…
The longer the heating element, the more water surface area it can heat. This results in faster overall heat-up times and greater efficiency.
Most modern homes will have two immersion heaters, one for the entire cylinder and one to heat the top half only. That gives you more options and flexibility without unnecessarily heating the entire tank.
Wattage and Running Costs of Immersion Heaters
This is a factor homeowners tend to ignore most of the time…
The wattage of your immersion heater plays a part in both how quickly it can heat water and how much it costs to run. You typically see standard immersion heaters in 3kW or 6kW options.
A 3kW immersion heater is slower but cheaper to run. It can take 2-3 hours to heat a full cylinder, so they’re best suited to off-peak electricity tariffs. If you’re on an Economy 7 plan, this is the one for you.
A 6kW heater will heat your water faster – typically 1-2 hours to heat a full cylinder. If you have a large household that regularly uses a lot of hot water, this will suit you better. But the 6kW draws more electricity per hour while heating.
For reference…
According to current prices, the average cost of having an immersion heater replaced by a professional is around £133. Whether you choose 3kW or 6kW should be driven by your household hot water usage patterns.
Safety Features on Immersion Heaters
It’s time for the serious stuff now…
Modern immersion heaters are fitted with built-in safety features that are not present on older versions. The reason you need to have these as standard on your new heater is that they are vital.
Thermostatic controls are usually set at around 60-65°C. The device monitors the water temperature and automatically cuts the heater off when it reaches the desired level. This stops the risk of overheating and energy wastage.
Thermal cut-out devices are backup safety measures. The idea is that if the thermostat fails, the thermal cut-out device steps in and kills the power to prevent any damage.
Water heaters have a lifespan of 8-12 years on average, so you want safety features that will continue to function throughout the entire life of your new unit. Sure, they cost a few pounds more upfront, but the peace of mind they provide is priceless.
DIY or Professional Installation?
Let me be brutally honest with you right now…
Installing an immersion heater is not difficult, but it’s also not a plug-and-play sort of job that anyone can do. You’ll need to drain the hot water cylinder, deal with electrical connections, and seal everything back up properly.
If you’re a confident plumber and electrician, then yes, you can probably do this yourself. However, most homeowners are far better off getting a professional in to do the work.
A botched DIY installation could lead to leaks, electrical faults, or damaged cylinders. A skilled electrician or plumber should be able to complete the job in 1-2 hours and get it working safely.
Labour charges for professional installation are around £50-100 per hour. Most jobs should run at £90-150 total labour charges. All that takes warranty coverage and peace of mind, and it’s money well spent.
Extra Considerations for the Savvy Buyer
Are you looking to squeeze maximum value from your new immersion heater purchase?
Consider fitting your new immersion heater to a timer. Timers allow you to only heat water during off-peak hours when electricity is cheaper. With 58% of UK homes using electric as their primary heating source, those savings really add up over time.
Insulation is another important consideration. A well-insulated hot water cylinder holds its heat much longer, meaning your immersion heater doesn’t need to work as often. Check your cylinder’s insulation is still in good shape, and replace it if needed while the cylinder is empty.
If you live in a hard water area, then a water softener is an excellent investment to protect your new immersion heater from limescale build-up. It’s an upfront cost that will pay dividends in the long term.
Time to Make Your Choice
When it comes down to it, choosing the right immersion heater replacement is simple when you understand your home’s unique needs:
- Cylinder size and picking the appropriate heater length
- Your water quality determines material choice
- Match wattage to household hot water usage
- Don’t skimp on safety features
- Hire a professional for best results and installation
If you get this decision right, you’ll have reliable hot water, lower energy bills, and a heater that serves you for years without issues. Rush it, or go for the lowest price? You’ll end up replacing it again far sooner than you’d like.
The fact is, if you take the time to get this choice correct, you’ll have easy, hassle-free hot water for the next decade.
