If you’re reading this, you’ve probably done your homework already. You know how heat pumps work, you know there’s a grant, and you’ve more or less decided you want one. The next step is choosing who designs and installs it.
That’s the right thing to worry about. As Dan, who runs Hohm, puts it:
“A heat pump is only as good as the person designing and installing it.”
Dan has been a heating engineer in Cheshire for 21 years. These are the five questions he’d ask any installer before signing anything.
- How will you calculate the size of the system?
The answer you want: a full room-by-room heat loss calculation, done at your property, given to you in writing before any kit is specified.
Anything else is a guess, and you’ll pay for it every winter.
Every heat pump has to be sized correctly for the home it is going into. The only way to do that accurately is a full heat loss calculation, a room-by-room assessment that accounts for insulation, glazing, floor area, and how much heat the building actually loses on a cold day.
Online calculators, including our own free estimate tool, are a useful starting point. But Dan is the first to say they only give a rough figure. The real number comes from a survey.
If an installer quotes a system size without carrying out this assessment, or does it over the phone in a few minutes, treat that quote with caution.
Get the size wrong and one of two things can happen.
A hugely oversized heat pump short-cycles, firing up and shutting down repeatedly without running efficiently.
An undersized one can’t keep the house warm when temperatures drop. Both outcomes are avoidable with proper design work from the start.
The right answer from an installer is a confirmed, written heat loss calculation before any equipment is specified.
- What flow temperature will my heat pump run at ?
Your heat pump flow temperature is how hot the water is when it leaves the heat pump and travels round to your radiators. It has a big effect on how much your heat pump costs to run, which is why it’s worth asking about.
The answer you want: a specific figure, usually somewhere between 35 and 45°C, and a clear explanation of which radiators or pipes (if any) need changing to get there.
Heat pumps are most efficient at these lower temperatures. A gas boiler runs at 70 to 80 degrees. An installer who designs a heat pump system to run at high flow temperatures could cost the homeowner in efficiency and running costs for the lifetime of the system.
Getting to low-flow temperatures usually means assessing whether existing radiators and pipes are adequately sized and upgrading where they fall short.
That’s the difference between a system running at a COP of 2.5 and one running above 4.0. That difference, compounded over a year of heating bills, is significant.
COP is how many units of heat you get for each unit of electricity you pay for, so the higher the number, the cheaper your heat pump is to run.
- Are you MCS certified, and which consumer code are you in?
The answer you want: yes to MCS, and membership of RECC or HIES.
You need two things, not one. Your installer has to be MCS certified, and they have to belong to an approved consumer code, which means RECC or HIES. Miss either, and you can’t claim the Boiler Upgrade Scheme grant. That’s £7,500 for most homes, or £9,000 if you’re on oil or LPG, gone over a box that wasn’t ticked. The scheme covers England and Wales, and the higher oil and LPG rate runs until 31 March 2027. Read our full guide to the air source heat pump grant for oil homes for more detail on eligibility.
MCS certification means the installer has met defined standards for training and installation quality. HOHM is MCS certified and a RECC member. You can verify that, and any other installer you are considering, at mcscertified.com before committing to anything.
- Can you show me real performance data from your installations?
The answer you want: yes, with a website link you can check for yourself.
Any installer can tell you their systems perform well.
Not all can prove it with independently verified data.
Heat Pump Monitor is a public, open-source platform that tracks real-world heat pump performance using meter-grade verified data from installations across the UK.
Installers who submit results are putting their work on a public leaderboard for anyone to inspect.
As of September 2026, one of our installations in Somerford, Congleton, Cheshire, ranks in the UK’s top 5 for air source heat pump efficiency on the all-time Heat Pump Monitor leaderboard. That data is publicly visible and independently verified. Ask any installer you speak to for something comparable.
- What does the handover process look like?
The answer you want: a clear explanation of how your system will be commissioned, a walk-through of the controls, and someone to call once it’s up and running.
Handover is the final stage, and it starts with commissioning.
Commissioning is how a heat pump gets set up, tested, and optimised once the physical installation is complete.
A poorly commissioned system can significantly underperform even when the hardware is installed correctly.
Before agreeing to anything, ask what the handover involves. Will the installer walk you through the controls in plain terms? Will they return to check performance after the system has been running for a few weeks?
What is their process if something is not working as expected?
At Hohm, we install, commission and fine-tune your system, then stay on hand for ongoing support.
What to do with the answers
Think of these five questions as your heat pump installer checklist. A good installer will be happy to answer all of them, and won’t find any of them awkward.
If an answer isn’t clear, ask them to explain it. The time to find out is before you sign a contract, not after the installation is complete.
A well-designed, properly commissioned heat pump will run efficiently for 20 years. The questions above take ten minutes to ask, so it’s worth doing before you commit.
What to expect if you ask us for a quote
At Hohm, we carry out a full heat loss calculation and site survey before recommending any system. If a heat pump is right for your home, we will design one that performs. If it is not, we will tell you that too.
You can see how our installations perform against every other installer in the country on the Heat Pump Monitor leaderboard. The data speaks for itself.
Get in touch to arrange a survey or use our free heat pump estimate tool to get an initial idea of costs.