Installing a heat pump water heater takes a pro about half a day to a full day. Reckon on 1,400 to 2,500 euros for the unit and 400 to 700 euros in labour, together often 1,800 to 3,200 euros. You need at least a dedicated 16A circuit, a condensate drain and enough air around the unit (think of a room of 20 m³ or more, or two air ducts). Watch out: if you want a grant, a registered installer has to fit it. Installing it yourself is technically allowed, but then you miss the grant, and you should only do the water-side connection yourself if you know what you are doing.
I’m Fred. Below I’ll walk you through all of it: how the thing works, where you put it, what you may do yourself, what you leave to an installer, and what it really costs. After this article you won’t need to look anywhere else.
How does a heat pump water heater actually work?
A heat pump water heater is a hot water tank with a small heat pump on top. That heat pump pulls warmth out of the air and uses it to heat your tap water. So your shower water, your tap water. Not your house.
The principle is exactly the reverse of a fridge. A fridge pulls warmth out of the inside and blows it outward. A heat pump water heater pulls warmth out of the surrounding air and puts it into the water in the tank.
That makes something clever happen. For 1 kWh of electricity you get roughly 3 kWh of heat back. A regular electric water heater turns 1 kWh of electricity into 1 kWh of heat, no more. So a heat pump water heater is roughly three times as efficient.
The flip side: the unit blows out cold air. That warmth has to come from somewhere, and what is left over is colder and drier air. You have to allow for that when placing it.
What is the COP and why does it matter?
COP stands for Coefficient of Performance. It’s the efficiency. A COP of 3 means: 3 parts heat per 1 part electricity.
What you look at:
| Term | What it means |
|---|---|
| COP | Efficiency at a single moment, at a fixed temperature |
| COP 3.0 | 3 kWh of heat per 1 kWh of electricity |
| Test condition | Often measured at 15 degrees air temperature and heating up to 55 degrees |
| Grant requirement | The unit has to meet the required minimum values to be eligible for a grant |
The warmer the air where the unit stands, the higher the COP. In a cold garage in January the efficiency drops. In a utility room at 18 degrees it performs better. That’s one of the most important choices when installing right away: where you put it.
Heat pump water heater on room air or on outside air?
There are two flavours. This decides how you install it.
On room air (recirculation). The unit draws air from the room it stands in and blows the cold air back into that same room, or through one short duct to the outside or to another room. Simple to fit. Condition: the room has to be big enough, otherwise it cools itself down.
On outside air or extract air (ducts). The unit is connected with two air ducts. One duct draws air in (from outside or from the mechanical ventilation), the other blows the cold air out. That way you don’t cool the room itself down. Handy if you want to put it in a small room or inside the home.
Some units can also recover heat from your ventilation extract air. That’s the warm, moist air from the kitchen and bathroom. That works well, but calls for a well-thought-out duct plan.
Where do you place a heat pump water heater?
The spot makes or breaks the efficiency. Four things count: enough air, not too cold, noise and drainage.
Good spots:
- Utility room. Often ideal. Warm enough, usually enough space, close to water and power.
- Garage. Fine on space, but can get cold in winter. Efficiency drops then.
- Shed or storeroom. Possible, provided it’s frost-free and has enough air volume.
- Loft or plant room. Possible, mind the condensate drain and noise under bedrooms.
Avoid:
- Small, closed cupboard spaces without ventilation. The unit cools the air down, which makes the efficiency collapse.
- Right next to a bedroom or living room without damping. See the section on noise.
- A living space you already heat anyway. Then the tank pulls warmth out of your heated air and you pay that back again through gas or electricity.
How much space and air do you need?
With a unit on room air the air volume is crucial. Manufacturers often name a minimum of around 20 m³ of space, sometimes more. Reckon, for example, a room of 3 by 3 metres at 2.5 metres high, that’s a good 22 m³. Smaller works, but then you have to use air ducts.
Also allow for:
- Space around the unit for the airflow and for maintenance, usually 20 to 50 cm clear on the intake and outlet side.
- Height. Many models are 1.70 to 2 metres tall. Measure your ceiling.
- Floor. A full 200-litre tank quickly weighs 250 to 300 kg with water. A solid, level floor is needed.
The units themselves often weigh 90 to 110 kg empty. Don’t carry that up a staircase on your own.
How do you install a heat pump water heater step by step?
This is the process in broad strokes. What you do yourself and what you leave is further down.
- Decide the spot and check the floor. Enough air, level solid floor, close to water and the consumer unit.
- Place the unit and level it. On the supplied feet or a solid base.
- Connect the air ducts (if needed). Intake and outlet. Insulate the ducts against condensation and heat loss. Keep bends short, every bend costs airflow.
- Connect the condensate drain. See below, people often forget this.
- Connect it on the water side. Cold water in, hot water out, plus an inlet safety group with a pressure relief valve and expansion. This is the trickiest part.
- Connect the wiring. To a dedicated circuit. See the wiring section.
- Fill, bleed and test. Fill the tank, bleed it, bring it up to pressure, only then apply power.
- Set it up. Temperature, eco mode, if applicable a Legionella programme and a day/night tariff.
What about the condensate drain?
The cold outlet air causes condensation. A heat pump water heater therefore produces water, often 0.5 to a few litres a day, depending on the moisture in the air.
That water has to go somewhere. Options:
- Connect it to a trap running to the drain or a floor gully.
- To a small condensate pump if there’s no drain laid to a fall.
Fit a trap or water seal, otherwise you get drain smell coming back. And lay the hose to a fall, water doesn’t run uphill. Forget this and after a week there’s a puddle under your tank.
What electrical connection do you need?
A heat pump water heater needs little power for the heat pump itself, often 300 to 600 watts. But most models also have an electric heating element for fast top-up heating and the Legionella programme. That element draws 1,500 to 2,000 watts.
Guidelines:
- A dedicated 16A circuit with an earth is the starting point. Many units run off an ordinary earthed socket, provided it’s on its own circuit.
- Some heavier or combined units want three-phase power. Always check the manual for your model.
- Don’t share the circuit with the washing machine or dryer. Peak load can trip the breaker.
Unsure about your consumer unit or need an extra circuit? Have an electrician do that. Working in the consumer unit without knowledge is dangerous.
Are you allowed to install a heat pump water heater yourself?
Technically you may do a great deal yourself. In practice there are two big catches.
Catch 1: the grant. If you want a grant, a registered installation firm with a company registration has to fit the unit. Do it yourself and you get no grant, even if your unit is on the approved list. With a grant that for a heat pump water heater quickly runs into a few hundred euros, that often weighs more than the labour costs you save.
Catch 2: the water-side connection. Connecting to the water main is precise work. You’re dealing with drinking water, with an inlet safety group against overpressure, and with Legionella risk. A bad connection gives leaks, backflow of contaminated water, or pressure problems. In many cases this has to follow the applicable regulations and sometimes be done by an approved installer.
What you can happily do yourself:
- Decide the spot and place the unit.
- Run and insulate the air ducts.
- Make the condensate drain.
What you’d better leave:
- The final water-side connection, especially if you’re unsure.
- Work in the consumer unit.
- Everything, if you want a grant, because then the whole installation has to go through a registered firm.
My down-to-earth advice: prepare everything you’re allowed to, and let a pro do the water- and grant-sensitive parts. That keeps the bill low and the grant in reach.
How do you prevent Legionella?
Legionella grows in lukewarm, standing water between roughly 20 and 50 degrees. Heat pump water heaters heat efficiently to lower temperatures, so you need a periodic Legionella programme that heats the tank up to at least 60 degrees now and then. Almost every modern unit has that function built in. Switch it on and leave it on. Don’t set the daily temperature too low to save power if that undermines the Legionella programme.
What tank size should you choose for a heat pump water heater?
Choose based on your household and shower habits. Too small and you’re standing cold in the shower, too big and you’re heating water you don’t use.
| Household | Recommended size |
|---|---|
| 1 to 2 people | 150 to 200 litres |
| 2 to 3 people | 200 to 250 litres |
| 3 to 5 people | 250 to 300 litres |
| Large family or a bath | 300 litres or more |
Rule of thumb: reckon about 50 to 60 litres of hot water per person per day for showering. A bath swallows 100 to 150 litres in one go, allow for that.
There are also models with an extra heat exchanger, so you can connect solar collectors or a boiler later. That costs a bit more, but gives flexibility.
What does a heat pump water heater cost with installation?
The total price breaks down into the unit, labour and possibly extra materials.
| Item | Indicative price |
|---|---|
| Unit 150 to 200 litres | 1,100 to 1,700 euros |
| Unit 250 to 300 litres | 1,500 to 2,500 euros |
| Installer labour | 400 to 700 euros |
| Extras (ducts, circuit, condensate pump) | 100 to 500 euros |
| Grant | a few hundred euros back off |
Roughly, with an average unit you land at 1,800 to 3,200 euros installed, and after the grant therefore a few hundred euros lower. The exact grant amount depends on the type of unit.
How much grant do you get?
For a heat pump water heater you can get a grant in many cases. The exact amount depends on the type and version of your unit. For a standard unit the amount is lower, for a version you can couple to a solar collector it’s higher, and for an extract-air heat pump water heater it’s highest.
The main conditions:
- You are the owner and occupant of an existing home, not new-build.
- The unit is new and is on the official list of eligible units.
- The installation was carried out by a registered installation firm with a company registration. Fitting it yourself falls outside the grant.
- You apply within the set deadline after installation and have the original invoice with the model number and installation date.
Important: the exact amounts change per year and per unit. I deliberately don’t name a fixed figure per model here, because that changes. Check the current amount for your specific unit with the relevant grant body and the official list of eligible units. Work out in advance what your model brings in, then you know exactly what you pay at the bottom line.
Watch out: for certain split air-to-water heat pumps with little refrigerant and a high GWP the grant can lapse due to European rules. For an ordinary heat pump water heater on room air that usually doesn’t come into play, but check it if in doubt.
What is the payback time?
That depends on what you’re replacing.
Replacing an electric water heater. You save a lot, because the heat pump water heater is about three times as efficient. Where an electric water heater for a family easily draws 3,000 to 4,000 kWh a year, a heat pump water heater does it on roughly 1,000 to 1,300 kWh. That’s hundreds of euros a year. Payback time often 3 to 6 years, faster with a grant.
Replacing a gas-fired combi boiler or geyser. The sum is less sharp, because gas for hot water is relatively cheap per unit. The saving then lies more in getting off gas and being future-proof. The payback time then varies more widely.
The lifespan of a heat pump water heater is on average 10 to 15 years, so within that time it pays for itself amply in most cases.
How much noise does a heat pump water heater make?
A heat pump water heater makes noise through the compressor and the fan. Reckon on roughly 40 to 55 dB, depending on the model and the setting. That’s comparable to a fridge up to a quiet extractor hood.
In practice:
- In a utility room or garage you barely notice it.
- Right under a bedroom the low-frequency hum can be disturbing. Then put it on vibration dampers and avoid direct mounting against a lightweight wall.
- A night mode or eco mode often runs more quietly.
Always check the stated dB figure of the specific model before you buy.
What maintenance does a heat pump water heater need?
Little, but not zero.
- Clean the air filter. Once or twice a year. A dirty filter costs efficiency.
- Check the condensate drain and trap. So nothing gets blocked.
- Test the pressure relief valve and inlet safety group. Lift it briefly once a year, that way you know it works.
- Check the anode. On tanks with a magnesium anode, every few years. It protects the tank against rust.
- Periodic servicing. Not legally required, but a service once every one to two years keeps it healthy and the warranty sometimes valid.
What brands are there?
Well-known brands on the market include Atlantic, Ariston (the Nuos range), Daikin, Panasonic, ATAG, Itho Daalderop, NIBE and Remeha. Price, noise, COP and capacity differ per model. Don’t only look at the price, but also at the COP, the noise level in dB, and whether the unit is on the official grant list if you want a grant.
Frequently asked questions
May I place a heat pump water heater myself?
Technically you may place the unit, run the air ducts and make the condensate drain. But if you want a grant, a registered installation firm has to do the installation. You leave the water-side connection to a pro if in doubt, because of the drinking water requirements and Legionella.
How much space do I need for a heat pump water heater?
With a unit on room air you often want at least around 20 m³ of air volume, plus clear space around it for the airflow and maintenance. Smaller rooms can work with two air ducts. Also measure your ceiling height, many units are 1.70 to 2 metres tall.
Does a heat pump water heater work in a cold garage?
Yes, but the efficiency drops at low temperatures. The colder the drawn-in air, the lower the COP. In a garage that heads towards freezing in winter it performs worse than in a utility room at 18 degrees. Preferably choose a slightly warmer room.
How much grant do I get for a heat pump water heater?
That depends on the type of unit and the version, and amounts change per year. A standard model is granted less, a version with a solar collector connection or an extract-air version more. Run your unit through the relevant grant body for the current amount.
What’s the difference with a regular electric water heater?
A regular electric water heater turns 1 kWh of electricity into 1 kWh of heat. A heat pump water heater pulls warmth out of the air and delivers roughly 3 kWh of heat per 1 kWh of electricity. That makes it about three times as efficient, with a lower energy bill as the result.
How long does a heat pump water heater last?
On average 10 to 15 years. With a clean filter, a working condensate drain and the odd service you get the top end of that.
Getting started
A heat pump water heater is one of the smartest ways to lower your hot water bill, provided you place and connect it well. Prepare what you’re allowed to do yourself, let a pro do the water- and grant-sensitive parts, and check your grant amount in advance.
Want to carry on working out your total energy use and where you can save even more? Then take a look at the energy-saving guide at energie-verpulveraar.fredsbouwtekeningen.nl. There you work out step by step where in the house you gain the most.