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What If a Heat Pump Doesn’t Work for My Home?

Installing a heat pump is a major decision. Even with a government grant, the homeowner may be committing thousands of pounds and making significant changes to a heating system that may have worked reliably for decades.

It is therefore reasonable to ask a much more important question than simply “How much could a heat pump save?”

What happens if I spend all that money and it doesn’t heat my house properly?

A correctly designed heat-pump system should be capable of heating the property it was designed for. The important issue is not simply choosing a reputable brand of heat pump, but making sure the whole heating system has been properly designed for the individual house before committing to the installation.

A Heat Pump Should Not Be a Guess

For an MCS-designed installation, the installer should calculate the heat loss of the property rather than simply replacing a boiler with a heat pump of a similar quoted output.

The calculation considers how quickly heat escapes through different parts of the building and determines how much heat the property requires under specified cold-weather design conditions.

The heating system can then be designed around that requirement.

This should include consideration of:

  • The calculated heat loss of the property.
  • The heat requirement of individual rooms.
  • Local outdoor design temperatures.
  • The output of the proposed heat pump in cold conditions.
  • Radiator or underfloor-heating output at the proposed water temperature.
  • Required radiator upgrades.
  • Pipework and water-flow requirements.
  • Hot-water requirements.
  • The proposed heating flow temperature.
  • Expected seasonal efficiency.
  • Any supplementary heating that forms part of the designed system.

Under the Boiler Upgrade Scheme, the heat pump itself must be sized to meet the property’s full space-heating requirement.

The homeowner should therefore be able to ask the installer:

“Show me the calculation demonstrating that this system will heat my house.”

That is a much more useful reassurance than simply being told that heat pumps work.

What If It Is Extremely Cold Outside?

Heat pumps do not suddenly stop producing heat simply because the weather becomes cold, but their output and efficiency vary with outdoor temperature.

This is why sizing matters.

The system should be designed against an appropriate outdoor design temperature for the property’s location rather than being sized around an average winter day.

A homeowner considering an installation should ask:

  • What outdoor temperature has the system been designed for?
  • How much heat does my house require at that temperature?
  • What output will this particular heat pump provide at that temperature?
  • What flow temperature will be required?
  • Will every room still reach its intended temperature?
  • Does the system contain supplementary electric heating and, if so, under what circumstances will it operate?

These questions turn a vague promise that “it will keep the house warm” into something that can actually be checked.

What If My Radiators Are Too Small?

This does not automatically mean that the house is unsuitable for a heat pump.

Traditional boilers commonly operate with hotter water than a heat pump ideally uses. A radiator that was adequate with very hot water may therefore need to be larger when operated at a lower temperature.

The solution may involve:

  • Larger radiators.
  • Double or triple-panel radiators.
  • Fan-assisted radiators.
  • Underfloor heating.
  • Improving insulation or draughtproofing to reduce the heat required by the room.
  • Designing the system for a somewhat higher flow temperature where appropriate.

This should be identified before installation, not discovered during the first cold spell afterwards.

Can I Keep My Gas Boiler as Backup?

Technically, heat pumps can exist in systems that also use fossil-fuel heating, and hybrid heating systems exist.

However, this creates an important choice for anyone relying on the Boiler Upgrade Scheme.

Under the current Boiler Upgrade Scheme rules, a heat pump installed alongside a fossil-fuel boiler as a hybrid or separate fossil-fuel backup system is not eligible for the grant.

A grant-funded heat pump is intended to replace the fossil-fuel heating system and must be capable of meeting the property’s heating requirements without relying on the gas boiler.

This means homeowners should not assume that they can claim the grant, leave the existing gas boiler connected as an emergency backup, and decide which system they prefer later.

If retaining gas backup is important, discuss this with the installer before applying for the grant and understand the financial consequences.

Could I Change Back to Gas Later?

A heat-pump installation does not make the building physically incapable of using another heating technology in the future.

Radiators, pipework and other changes made for a heat pump can often remain useful parts of a wet central-heating system. Larger radiators, for example, are not a disadvantage if another heat source is subsequently installed.

However, changing back would involve additional expense and potentially new installation work. Gas availability, future regulations, the condition of existing infrastructure and the cost of reconnecting or installing equipment would all need to be considered at that time.

A heat pump should therefore be treated as a significant long-term heating decision rather than something to install experimentally because a grant happens to be available.

What If the Installation Performs Badly?

Poor heat-pump experiences do exist. They do not necessarily demonstrate that the technology itself cannot heat a house.

Problems can result from:

  • Incorrect sizing.
  • Inaccurate heat-loss calculations.
  • Radiators that cannot deliver enough heat at the chosen flow temperature.
  • Poor controls or commissioning.
  • Incorrect weather compensation settings.
  • Inadequate water flow.
  • Poorly insulated pipework.
  • Installation faults.
  • Unrealistic expectations about how the system should be operated.

This is why the quality of the system design and installation matters as much as the heat pump itself.

If an installer cannot clearly explain the design figures or becomes uncomfortable when asked to demonstrate how the proposed system meets the calculated heating demand, obtaining another quotation is sensible.

Get More Than One Design, Not Just More Than One Price

Three installers quoting three different prices does not necessarily provide three useful comparisons.

Ask each installer for the important design information.

Compare:

  • Calculated property heat loss.
  • Proposed heat-pump model and size.
  • Design outdoor temperature.
  • Proposed flow temperature.
  • Radiators that need replacing.
  • Expected seasonal efficiency.
  • Estimated annual electricity consumption.
  • Hot-water arrangement.
  • Electrical work required.
  • Noise assessment and outdoor-unit location.
  • Warranty.
  • What happens if the completed system does not achieve the design temperatures.

Large differences between installers’ heat-loss calculations or proposed system sizes deserve an explanation before choosing either one.

Do Not Let a Grant Create an Artificial Deadline

A grant can make a heat pump substantially cheaper, but the existence of a grant is not by itself a reason to install one.

The current Boiler Upgrade Scheme offers substantial support towards eligible installations, but government schemes, grant amounts and eligibility rules can change.

That creates an understandable temptation to act before support disappears.

However, spending thousands of pounds quickly to avoid potentially losing a grant can be more expensive than losing the grant itself if the resulting system is unsuitable.

The purpose of the grant should be to make the right installation cheaper — not to make a homeowner rush into the wrong installation.

Will a Heat Pump Increase the Value of My House?

This is much harder to predict.

A modern, efficient heating system may make a property more attractive to some buyers, particularly when combined with good insulation, solar panels, battery storage and low running costs.

Other buyers may still prefer a familiar gas heating system.

Property value is influenced by location, property type, energy performance, running costs, buyer preferences and the quality and age of the installation. It would therefore be unwise to justify the full cost of a heat pump on the assumption that the same amount will automatically be added to the sale price.

A more useful question is:

Would this installation make the house cheaper, more comfortable and more attractive to live in while I own it?

Any increase in resale value can then be treated as an additional benefit rather than being required to make the investment worthwhile.

A Heat Pump Should Pass a “No Regrets” Test

Before committing to an installation, a homeowner should be able to answer yes to these questions:

  • Has a proper room-by-room heat-loss calculation been completed?
  • Has the installer shown that the proposed heat pump can meet the calculated heating requirement?
  • Do I know the outdoor temperature for which the system has been designed?
  • Do I know which radiators need changing and why?
  • Do I understand the expected electricity consumption rather than only the heat pump’s headline efficiency?
  • Do I understand how hot water will be provided?
  • Do I know what electrical upgrades are required?
  • Have I obtained more than one quotation?
  • Have I compared the proposed designs rather than simply comparing prices?
  • Do I understand the warranty and consumer protection available?
  • Have I asked what happens if rooms fail to reach their design temperatures?
  • Can I afford the installation without relying on uncertain future savings or an assumed increase in property value?
  • Would I still consider the installation worthwhile if the property gained no additional resale value?
  • Am I choosing the system because it suits the house rather than because I am frightened of missing a grant?

If several of those questions cannot yet be answered, the decision does not necessarily need to be “no.”

It may simply need to be:

“Not yet — I need more information.”

The Aim Is Confidence, Not Persuasion

There is no need for every home to have a heat pump.

Some properties are particularly straightforward candidates. Others may require radiator changes, insulation improvements or significant installation work. In some circumstances another heating solution may currently make more sense.

The purpose of researching a heat pump should therefore not be to find enough positive information to justify buying one.

It should be to reach the point where the homeowner knows:

how much heat the house needs, how the proposed system will provide it, approximately what it will cost to operate, what could go wrong, what protection exists if it does, and whether the financial commitment makes sense.

At that point, deciding not to install a heat pump can be just as successful an outcome as deciding to install one.

The problem has been solved when the homeowner can make either decision with confidence.