Heat pump regrets, and how to avoid them.

Some do, and the regret is worth taking seriously rather than waving away. Complaints on UK installer forums have risen sharply in recent years. But when you ask actual owners, the picture flips: around 94 per cent of UK heat-pump owners say they are satisfied, higher than the 85 per cent for mains-gas boilers. Almost all the regret that does exist traces to a bad install, the wrong house, or the wrong tariff, not to the technology.

Both halves of that are true at once, which is why the question is confusing from the outside. Take the satisfaction first. The Electrify Research Homeowner Electrification Tracker, which has surveyed more than 4,000 UK homeowners across three waves, found 94 per cent of heat-pump owners satisfied (44 per cent "satisfied", 50 per cent "extremely satisfied"), against 85 per cent for gas-boiler owners. A separate Nesta user survey reached the same place from a different angle: overall satisfaction on par with gas boilers, with 73 per cent as satisfied as or more satisfied than their old system. The one attribute where heat-pump owners scored lower was ease of use and the controls, not warmth and not reliability.

Now the other half. The visible unhappiness online is real, and it is concentrated. An analysis by the trade outlet Installer Online of 61,483 posts on the Renewable Heating Hub forum found posts using poor-install language ("cowboy", "rogue installer", "commissioning failure", "not MCS compliant") rose from 25 in 2021 to 475 in 2024. The outlet's own conclusion was blunt: installation-quality failures, not technology limitations, drive the dissatisfaction. The surge tracks the 2022 launch of the Boiler Upgrade Scheme grant, which grew demand faster than the trained-installer base could keep up.

The summary, then. A well-installed heat pump satisfies about nine owners in ten. The regret you read about is real, but it clusters in a minority of bad installs, and almost all of it was avoidable at the quote stage. The rest of this guide is the three places it goes wrong, and what to do about each.

Sort the genuine regret stories and nearly all of them fall into three buckets. They are not equal in size. The first is far more common than the other two put together, and it is also the most avoidable.

1. A rushed install. The unit is the wrong size, the flow temperature is left too high, or the system is never properly commissioned. The heat pump runs, but inefficiently and expensively, and the home can feel underheated. This is the dominant cause, and it is set entirely at the design and quote stage. It is covered in Regret one: a rushed install below.

2. The wrong house, or the right house in the wrong order. A poorly insulated home is not unheatable, but it has to be sized for honestly, and doing the fabric work after the sizing rather than before can strand an oversized unit. See Regret two: the wrong house below.

3. The wrong tariff. Running a heat pump on the standard electricity cap when a heat-pump tariff plus a little scheduling would cut the bill by a few hundred pounds a year, money paid for nothing and the easiest of the three regrets to fix. See Regret three: the wrong tariff below.

This is where most of the regret lives. A heat pump is a designed system, not an appliance you swap in, and a rushed design shows up as high bills and a home that never feels quite warm enough. When Installer Online sorted the forum complaints by type, the same handful of faults came up again and again.

The most frequent heat-pump install complaints on a UK installer forum, by category, counted from posts using poor-install language between 2021 and 2026.

Install fault	Complaint posts
Oversized unit, short-cycling	453
Flow temperature set too high	342
Missing commissioning paperwork	187
Undersized, cannot hold temperature	177
Weather compensation left switched off	78
Inadequate heat-loss calculation	—

Oversized unit, short-cycling

453

Flow temperature set too high

342

Missing commissioning paperwork

187

Undersized, cannot hold temperature

177

Weather compensation left switched off

78

Inadequate heat-loss calculation

—

The pattern is worth reading closely, because it points straight at the questions to ask. Oversizing is the single biggest one. An oversized heat pump cannot run gently, so it short-cycles, clicking on and off all day. That wears the kit out and pushes the running cost up. A flow temperature left at 55 to 60°C, the way a boiler runs, instead of the 35 to 45°C a heat pump wants, quietly wrecks efficiency: every extra degree of flow temperature costs running cost. Missing commissioning means the installer never tuned the system to the home before leaving. Every one of these is the install failing, not the heat pump.

The size of the gap is measurable. The Energy Saving Trust's Electrification of Heat trial, across a broad mix of real UK homes, recorded a median seasonal efficiency (SPFH4, the real-world measured version of the SCOP figure used elsewhere on this page) of about 2.80. The volunteer fleet on HeatpumpMonitor.org, where owners tend to choose careful installers and monitor closely, averages about 3.87 on the same measure. That is the same class of hardware producing very different results, and the difference is set almost entirely by design and commissioning over a real winter. A good install can run a third more efficiently than a rushed one in the same house. The running-costs guide explains what SCOP is and why a bad install tanks it.

You can see the same faults in the specifics homeowners report. A common one is a heat-loss survey that designs every room to 21°C, rather than the room-by-room temperatures the MCS method uses, which inflates the calculated heat loss and triggers radiator swaps that were never needed. Another is undersizing a unit that sits right on the edge of the home's demand, then discovering that manufacturer output figures do not include the defrost cycle, so real output on a cold day falls short. Emitter size is the lever that lets a heat pump run at a low, efficient flow temperature, which is why the property-suitability guide treats radiators as a first-order question rather than a detail.

The reassuring part is that a rushed install is preventable, and you prevent it before you sign. The faults in the table are exactly the things a careful quote gets right and a quick one skips, which is why we wrote them up as the nine questions to ask your installer. Asking them at the quote stage is the single most effective thing you can do to stay out of this column.

The second regret is about the building, and it is more often a sequencing mistake than a hard no. A solid-walled, draughty, uninsulated home is not unheatable by a heat pump, but it loses more heat, so it has to be sized for that honestly. The regret comes from pretending the fabric does not matter, or from doing things in the wrong order.

The principle experienced installers come back to is that if heat loss, emitters and the heat pump are all matched to each other, almost any envelope can be heated comfortably. Poor fabric does not force a high flow temperature on you. You can trade it for bigger radiators instead, keeping the flow temperature low and the efficiency high. What you cannot do is ignore it. A home that leaks heat needs either fabric work or larger emitters, and a quote that skips both is the one that leads to a cold living room in January.

The sequencing trap is subtler and catches careful people. If you size and install the heat pump first, then insulate later, you can end up with a unit that is now too big for the improved, lower-heat-loss home. An oversized unit short-cycles, which drops you straight back into Regret one. So the rule is: insulate before you size, or have the installer design the system around the fabric work you already know you are going to do. Either order works, as long as the design accounts for the home you will end up with. Doing the fabric as an unplanned afterthought is the version that goes wrong.

This is well-trodden ground for the older UK housing stock, and it is genuinely solvable. The Victorian-house guide works through solid-wall brick, and the 1930s-house guide through cavity-walled semis, both with realistic efficiency bands by fabric state. For the general question of what to check and what to fix first, the property-suitability guide is the place to start. The regret here is almost never "my house was wrong". It is "we did it in the wrong order".

The third regret costs real money and is the easiest of the three to fix, which is why it is the most annoying to discover late. It is running a perfectly good heat pump on the standard electricity price cap, when a heat-pump tariff plus a little scheduling would cut the bill. The same hardware in the same house can sit a few hundred pounds a year apart, purely on the tariff.

On the right tariff, the heat pump now runs a little below mains gas, about £130 a year cheaper here. That margin only opened up with the July 2026 price cap, which pushed gas up sharply, and it needs the good install plus the heat-pump tariff to hold. On the standard cap the same heat pump is still dearer than gas. That is today's energy pricing, not a fault in the heat pump. UK electricity carries social and environmental levies that gas is spared, which keeps it dear relative to gas even now, and the government has said it plans to rebalance the two. The chart shows running cost only, too: it leaves out the £7,500 Boiler Upgrade Scheme grant and the fact that most people are replacing a boiler that was near the end of its life anyway. The running-costs guide and the cost-and-grants guide work through the full gas-versus-heat-pump picture.

The £300 is not a hardware upgrade or a fabric improvement. It is the same machine in the same home, billed two ways. Heat-pump tariffs such as Octopus Cosy price a chunk of the day cheaply, so if you pre-heat the home and reheat the hot-water cylinder in the cheap window and stay out of the early-evening peak, the effective rate drops below the cap. Left on the cap, or left on a heat-pump tariff but never scheduled, you pay the higher bar.

Two honest caveats. The cheap window only helps if you actually shift load into it, and a well-insulated home holds the pre-heat better than a leaky one, so this regret and the last one are linked. And a home battery helps by time-shifting when you draw from the grid, rather than by pulsing the heat pump on and off, which is a common misunderstanding of how these tariffs save money. The running-costs guide works through the tariffs and the scheduling discipline in detail. The point for this guide is narrow: check the tariff question before you sign, not a year in.

All three regrets share one feature: they are decided before the install, not during it. That works in your favour, because it means the way to avoid them is the same in every case. Get the decision right at the quote stage, and the most likely outcome is the 94-per-cent-satisfied one, not the forum-complaint one.

Interrogate the quote. The faults in the complaint table are all things a careful design gets right and a rushed one skips, so the fix is to ask. How was the heat loss calculated? What flow temperature is the system designed around? Is the unit sized to the home rather than rounded up? Our guide to the questions to ask an installer turns this into nine specific questions, each with what a good answer sounds like and the red flag that means get another quote.

Do the fabric first, or design around it. If your home needs insulation, either do it before the heat pump is sized, or make sure the installer designs the system around the work you are committed to. That keeps the unit matched to the home you will actually have, not the one you have today. Bigger radiators are a valid alternative to fabric work, as long as somebody does the sum.

Sort the tariff early. Plan to move onto a heat-pump electricity tariff and to use its cheap window. It is worth a few hundred pounds a year for very little effort, and it is much easier to set up at the start than to discover a year later.

And the most important one. Be honest about whether your home is ready at all. For some homes today the right answer is not yet: the fabric needs work first, or the sums do not land until something changes. Knowing that before you commit is not a disappointment, it is how you avoid the most expensive regret of all. That is exactly what the HeatPass check is built to tell you. It reads your home's EPC record, asks the few things it cannot, and gives a straight verdict, including a Not Yet with a plan when that is the honest answer. If you want to understand the technology first, start with how a heat pump actually works.