As demand for heat pumps continues to grow across the UK, homeowners are being urged to carefully vet installers amid concerns that a lack of expertise could lead to poor system performance and higher running costs.

Dwellow, nationwide renewables experts, are on a mission to arm householders with key questions to ask before committing to a costly installation, warning that “not all installers are created equal”.

Poor installation practices risk undermining confidence in heat pumps, particularly when homeowners are left with underperforming systems.

“The technology works really well, but only when it’s designed and installed properly,” Ian McLaren, Dwellow co-founder, says. “Choosing the right installer is just as important as choosing the right system. Otherwise it’s a very expensive mistake.”

All installers carrying out heat pump installations under government schemes must be MCS (Microgeneration Certification Scheme) accredited. However, Dwellow says this should be seen as a baseline rather than a guarantee of quality.

“Being MCS accredited is essential, but it doesn’t automatically mean the installer is an expert in heat pump design,” says McLaren. “Homeowners should treat it as a minimum requirement, not a mark of excellence.”

Key questions every homeowner should ask

How have you sized the heat pump?

Reputable installers should carry out a full home heat loss survey and provide calculations to determine the correct system size required.

To do that properly, they look at a few key things.

First is the fabric of the building, so your walls, floors, roof, windows and doors. They assess how well each of those elements retains heat, which depends on things like insulation levels, construction type, and glazing.

Then they look at each room's size, ceiling heights, and how the space is actually used. A large open-plan kitchen, for example, behaves very differently to a small bedroom.

Ventilation and air leakage are also worked out, which can make a big difference, especially in older or draftier homes.

McLaren explains: “All of that feeds into the all-important heat loss figure, measured in kilowatts, for each room and for the property as a whole.

“That number is what tells us how big the heat pump needs to be. It’s not guesswork or rules of thumb. Once we’ve got that, we can then design the rest of the system around it. This includes radiator sizing, flow temperatures, and how the system will run efficiently day to day.

“If your home has a heat loss of around 8kW, which is typical in the UK, and someone is recommending a 14kW unit, alarm bells should ring. Oversizing leads to inefficiency, cycling, and higher running costs.”

Can you explain your system design?

Unlike traditional gas or oil boilers, heat pumps rely heavily on correct system design to perform efficiently. A competent installer should be able to clearly explain their design decisions.

“With a boiler, you can often mount it on the wall and it will work without much thought,” McLaren explained. “Heat pumps are completely different because they need to be properly designed for the home. If the design is wrong, the system won’t perform as it should.”

Dwellow warns that some installers entering the market from boiler backgrounds may lack the design experience required for heat pump systems.

“You want someone who understands heat pumps inside out, not someone who’s just added them to their offering because demand has increased,” McLaren added.

“It’s important to probe your engineer,” McLaren said. “If they can’t explain why they’ve designed the system a certain way, they probably don’t understand it properly.”

Homeowners are also advised to question the use of components such as buffers and zoning. Zoned rooms and multiple thermostats work well with gas boilers, but they undermine heat pump efficiency because they cause it to switch on and off frequently, which it isn’t designed to do.

“These are often added unnecessarily,” McLaren added. “Ask why they’re being included because a good installer will justify every part of the system.”

What heat pump brand are you recommending and why?

Make sure the brand of heat pump is right for you, not just the installer. Some manufacturers offer installers incentives to use their products, or they have been known to source the cheapest unit on the market to increase their margin.

If one installer quotes a premium heat pump and another offers a similar price for an entry-level model, the quotes aren’t directly comparable. It may indicate one installer is applying a large margin to a lower-cost product.

Do your research and look on a merchant website to ensure you’re getting a fair price.

Are the controls and app easy to use?

Modern heat pumps should include an intuitive control panel and app-based monitoring. This allows installers and manufacturers to diagnose problems and make adjustments to your system remotely. Both should be simple and intuitive to use.

“Ask whether the system includes remote monitoring and whether your installer has access to performance data,” McLaren said. “If they don’t offer this, it may indicate they’re not interested in how the system performs after installation.”

What warranty and aftercare is offered?

Aftercare is a critical but often overlooked part of heat pump ownership.

“Most manufacturers offer warranties of seven years or more,” McLaren said. “If an installer is offering significantly less, it’s worth asking why.”

Dwellow says homeowners should also expect ongoing support. “A good installer will check in after installation, monitor performance, and suggest improvements where needed,” said co-founder Adam Raw. “Heat pumps aren’t a fit-and-forget technology, they benefit from optimisation over time.”