Tankless Water Heater Installation Cost

Want to know about tankless water heater costs in 2026?

Tankless water heater installation costs between £200 and £1,500 for the unit, plus £240 to £500 in labour to fit it. The exact price depends on the type of heater you choose and how much work the installation involves.

The biggest cost driver is whether the job is a like-for-like replacement or a brand-new install. Swapping an old unit for a similar one reuses the existing pipework, wiring, and venting, so it costs far less than a new install that needs fresh circuits, a gas line, or a flue. Gas heaters also cost more to fit than electric ones, as they must be installed by a Gas Safe engineer.

How Much is Tankless Water Heater Installation?

The cost of a tankless water heater installation depends on whether you are installing a new system or replacing an old one, and whether it is powered with electric or gas.

What type of tankless water heater are you looking to install?

Electric

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Your location will also have a bearing on cost. London and the South East are more expensive than other parts of the UK. You should expect to pay more for the services of an electrician or plumber as their hourly rates are higher.

The average cost for:

• Replacing an old tankless water heater: £1,080 - £1,450
• Installing a completely new system: £1,450 - £2,000

Replacing a like-for-like heater is often cheaper because the circuit, wiring, and venting are already in place, so the work is mainly supplying the new unit and reconnecting it. A new installation costs more. For electric models it can involve new wiring, a consumer unit upgrade, and RCD protection, while gas models may need a new gas pipe, flue, and condensate pipe, plus testing and certification.

Tankless Water Heater Installation Prices

If you are installing a tankless water heating system in a larger property, you may need more than one unit. In this case, you might have a unit for the bathroom and a separate unit for the kitchen.

The costs in this case are likely to double. This is because each unit needs individual pipework or wiring.

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What are the Supply Costs of a Tankless Water Heater?

Tankless water heaters are available to suit most budgets. Cheaper tankless heaters tend to be electric and are used for sinks and showers. They cost less than a heater designed to supply hot water for the whole house.

Gas heaters tend to cost more than electric ones. This is because they are a more complex build, with a higher hot water output.

When you are looking to buy a tankless heater, take into consideration the size of your home and the amount of hot water you generally use. More expensive heaters have features including Wi-Fi connectivity and Smart Controls. They handle simultaneous usage and are often made with better quality, more reliable materials, resulting in a longer lifespan.

Electric Tankless Heaters

Gas Tankless Heaters

Additional Costs

If you consider additional costs for a new tankless heater, there won’t be any unpleasant surprises. Here are the average costs of some of the things you might want to add to your budget:

• Removal and disposal of an old heater or cylinder - £100 - £250, depending on the unit type, ease of access, and disposal method
• Upgrading electrics - £100 - £300
• Scaffolding (if the unit is outdoors at a height) - £80 - £100 for a week’s hire
• Aesthetics – Making good, boxing in, plastering, replacing tiles and re-decorating - £50 - £200 depending on the amount of work and the tradesperson you are using
• Reinforcement – Works may be needed to reinforce the area where the heater is located - £50 - £100
• Adding smart controls, such as a smart thermostat - £100 - £300

Other additional costs to consider are the payment for a maintenance or service plan, which you might want to consider with a gas appliance. Regular maintenance will help the system work efficiently and prolong its lifespan.

Labour Costs and Timescales

A tankless water heater can be installed by:

• An electrician - £50 - £60 an hour (£80 or more in London)
• A plumber - £60 - £75 an hour (£80 - £100 in London)
• A gas engineer - £30 - £50 an hour

Which trade you need depends on the heater, not the hourly rate. A gas tankless heater must legally be installed by a Gas Safe registered engineer, while an electric one is usually fitted by an electrician, and must use a Part P registered electrician if new circuits or a consumer unit are involved.

A plumber typically handles the water connections, but any gas or electrical work must be carried out and signed off by the correctly qualified trade. So the cheapest hourly rate is not the deciding factor. What matters is choosing the right trade for your type of unit.

Cost Factors for Tankless Water Heater Installation

Cost factors include:

• Gas or electric – Gas units cost more to install than electric models, as they are more complex and need specialist gas work.
• The model you choose – Premium brands, smart features such as Wi-Fi controls, and more efficient condensing units cost more than basic models.
• Existing plumbing and electrics – Reusing the wiring and pipework already in place keeps costs down, while laying new runs adds to materials and labour.
• Size and flow rate – Higher flow-rate units that supply several outlets at once cost more than smaller, single-outlet models, and may need electrical or gas upgrades to run.
• Indoor or outdoor placement – Indoor fitting is usually cheaper. A hard-to-reach spot or an outdoor unit adds labour, weatherproofing, and a mounting bracket, plus scaffolding if it sits at height.
• Upgrades – Older homes may need a new consumer unit (fuse box) or reworked pipework for the gas supply, which adds to the cost.
• Your location – Labour rates run higher in London and the South East, so where you live affects the final price.

Building Regulations Tankless Water Heater Installation

A gas tankless water heater should be installed by a professional who is registered under an approved Gas Safe scheme. Building regulations include rules on the installation of vents and flues, condense and gas pipes.

Installing an electric tankless water heater doesn’t need to be signed off by a registered electrician, but if you are having upgrades such as a new consumer unit or a new circuit, then you will need a Part P registered electrician and the work must be signed off and certificated.

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Types of Tankless Water Heaters

The main types of tankless water heater, also called instant water heaters, are electric and gas, with gas models further divided into condensing and non-condensing units. Costs vary by fuel type (gas, propane, or electric) and by capacity, as some are sized to heat a single outlet such as one bathroom, while others supply the whole house.

Each type has its own features, venting needs, and maintenance demands, so compare the options below before choosing:

Electric Tankless Water Heater

Ideal for small properties which lack space for a traditional tank.

Pros

• ✔ Cheaper to install than gas
• ✔ Excellent Energy efficiency
• ✔ Longer lifespan than a traditional tank because the system has fewer components

Cons

• ✖ May need electrical upgrades before installation
• ✖ No hot water during a power outage
• ✖ A larger home will need a more expensive tank, or more than one tank, to provide water from multiple outlets at the same time

Gas Tankless Hot Water Heater

Gas tankless heaters are often recommended for larger homes where families use hot water simultaneously.

Pros

• ✔ Higher flow rates provide hot water easily from more than one outlet at the same time
• ✔ Better at heating water to the desired temperature in cold weather
• ✔ Hot water even if there’s no electricity

Cons

• ✖ Installation costs are higher than those of electric heaters because of extras like vents and flues
• ✖ May need to upgrade pipework
• ✖ Must be installed by a Gas Safe engineer

Condensing Tankless Water Heaters

A condensing water heater has an extra heat exchanger. When energy comes from the flue, the second heat exchanger captures it, rather than letting it escape, and converts it into heat. This means the system works more efficiently because it reduces heat loss.

Pros

• ✔ Reduced running costs
• ✔ More efficient use of heat
• ✔ Higher flow rate

Cons

• ✖ More expensive to buy than a non-condensing model
• ✖ More complex to install

Non-Condensing Tankless Water Heaters

Non-condensing water heaters only have one heat exchange, so heat is lost when it escapes from the flue into the atmosphere, reducing the efficiency of the unit.

Pros

• ✔ Cheaper than condensing units
• ✔ Less maintenance required
• ✔ Easier installation

Cons

• ✖ Less efficient than the condensing model
• ✖ Higher running costs

Alternative Types of Water Heating Systems

Alternative water heating systems to a tankless unit include combi, regular, and system boilers, solar water heating, and heat pump water heaters. If a tankless heater is not right for your home, here is how each option compares:

Combi Boilers

Combi boilers are very common in UK homes. They provide hot water and heating without the need for a hot water tank or a cylinder.

• Average cost to supply and install - £2,600

Pros

• ✔ Instant hot water and heat
• ✔ Easy to install
• ✔ Energy efficient

Cons

• ✖ Flow rate is reduced when two or more outlets are used at the same time
• ✖ Can’t combine with solar heating systems

Regular Boilers

Regular boilers use a storage tank, which is usually in the loft and a hot water cylinder. They are suited to homes with low water pressure because the water is supplied using gravity rather than pressure.

• Average cost to supply and install - £2,200

Pros

• ✔ High flow rates
• ✔ Ideal with large households
• ✔ Works with solar heating systems

Cons

• ✖ You may need to wait for the hot water to heat up if it has been used
• ✖ You need space for the cylinder and cold-water tank.

System Boilers

System boilers are similar to regular boilers, but they take cold water from the mains, where it is stored and heated in a hot water cylinder.

• Average cost to supply and install - £3,150

Pros

• ✔ Ideal for large families
• ✔ No need for a cold-water tank
• ✔ System boilers combine well with underfloor heating

Cons

• ✖ Maybe wait for hot water if the water in the cylinder has been used
• ✖ Space needed for the water cylinder
• ✖ If you have low pressure from the mains, your flow rate won’t be ideal

Solar Water Heating

Solar water heating systems use solar panels on your roof and a water cylinder. The sun heats up the solar panels, which then heat the water in the cylinder.

• Average cost to supply and install - £5,000.

Pros

• ✔ Can reduce your monthly fuel bills by between £10 and £20
• ✔ Ideal if you want to reduce your carbon footprint
• ✔ Low-maintenance water heating option

Cons

• ✖ May be more expensive to install than a traditional hot water system
• ✖ Likely to need another form of heating your water during the winter

Heat Pump Water Heaters

A heat pump water heater takes air from the outside and uses electricity to heat it up, and then transfers it to a hot water cylinder.

• Average cost to supply and install a heat pump water heater - £8,000.

Pros

• ✔ Energy efficient -reduced fuel bills
• ✔ Long lifespan (between 12 and 15 years)
• ✔ Reduced carbon footprint

Cons

• ✖ Expensive upfront costs
• ✖ Takes more time to heat water than other conventional systems
• ✖ Needs space and outside wall for installation

Checklist: Hiring an Installer to Fit a Tankless Water Heater

Consider these key points before hiring an installer for this job:

• Are they Gas Safe or Part P registered? A gas tankless heater must be fitted by a Gas Safe registered engineer, while any new electrical circuits need a Part P registered electrician.
• Will they handle building control sign-off? Some installations need to be notified to building control, so ask whether they’ll register the work and sort your compliance certificate, or whether you’ll need to arrange it with your local authority.
• Do they have public liability insurance? It isn’t a legal requirement, but it’s worth checking in case something goes wrong while they’re working on your gas or water system.
• Is removing your old unit included? Confirm that taking out and disposing of your existing heater or cylinder is covered in the quote, rather than added as an extra later.
• How much experience do they have with tankless systems? You ideally want someone with a few years of experience fitting on-demand water heaters, not just traditional hot water tanks.
• Can they show examples of similar work? Ask to see photos of previous tankless installs, or check their MyJobQuote profile for examples of past jobs.
• Do they have positive reviews? Read through the ratings and feedback left by other homeowners on their MyJobQuote profile before you decide.

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