If you have started researching heat pumps, you have probably come across several efficiency figures.

COP.

SPF.

SCOP.

They can make comparing heat pumps feel more complicated than it needs to be.

But understanding the difference is useful because these figures can tell you something important about how a heat pump performs.

The key is knowing what they do not tell you.

A heat pump can have an impressive efficiency figure on the product specification.

That does not automatically mean it will achieve exactly the same performance once installed in your home.

The property, heating system, outdoor conditions, heating water temperature, controls, commissioning and system design all matter.

There is also an increasingly important standards and regulatory context.

Heat pump systems installed today need to be designed within current technical requirements, while Scottish funding and new build rules are placing greater emphasis on correctly designed low emission heating.

So rather than choosing a heat pump simply because one number looks better than another, it helps to understand what each figure represents and how it relates to the complete system.

COP stands for Coefficient of Performance.

It describes the relationship between the useful heat a heat pump provides and the electricity it uses under particular operating conditions.

For example, if a heat pump is operating at a COP of 4, it is providing approximately:

4 units of useful heat

for every:

1 unit of electricity consumed

A heat pump can do this because it is not producing all of the heat directly from electricity.

An air source heat pump collects heat from the outside air.

A ground source heat pump collects heat from the ground.

Electricity powers the process that transfers and raises the temperature of that heat so it can be used inside the home.

Imagine a heat pump consumes:

1 kWh of electricity

and provides:

4 kWh of useful heat

The COP under those operating conditions is:

COP 4

The calculation is:

Useful Heat Output ÷ Electrical Energy Input = COP

But there is an important point.

COP is not fixed.

It changes as operating conditions change.

A heat pump does not operate under identical conditions throughout the year.

An air source heat pump may be collecting heat from mild outside air one day and much colder air another.

The heating system may require water at one temperature for space heating and a higher temperature for domestic hot water.

Different homes also require different heating water temperatures.

All of these things affect how hard the heat pump needs to work.

In general, the smaller the temperature difference between the heat source and the temperature required by the heating system, the easier it is for the heat pump to operate efficiently.

That is one reason system design matters so much.

SPF stands for Seasonal Performance Factor.
Instead of looking at performance at one moment, SPF considers the relationship between useful heat delivered and electricity consumed across a longer period.
In simple terms:
COP is a snapshot.
SPF looks at performance over time.
For example, if a system delivered:
12,000 kWh of useful heat
while using:
3,000 kWh of electricity
within the relevant measurement boundary, its SPF would be approximately:
4
The principle is:
Total Useful Heat Delivered ÷ Total Electricity Used = SPF
This is useful because a heating season includes changing outdoor temperatures, changing heating demand and different operating conditions.

COP

Shows efficiency under a particular set of operating conditions.

SPF

Shows performance over a longer period.

COP helps describe the heat pump at a particular point.

SPF provides a broader view of the installed system.

You may also see SCOP on heat pump product information.

SCOP stands for Seasonal Coefficient of Performance.

It is normally derived from standardised testing intended to allow products to be compared on a consistent basis.

That makes SCOP useful when comparing equipment.

But it is not exactly the same as monitored performance in your actual home.

A useful distinction is:

SCOP helps compare products.

SPF can help describe real installed system performance.

That difference matters because a heat pump does not operate in standard test conditions once it has been installed in a real Scottish property.

It is tempting to look at two specification sheets and choose the heat pump with the larger efficiency figure.

But you first need to know the operating conditions behind those numbers.

For example, a heat pump operating with relatively mild outdoor air and low heating water temperature is performing a different task from one operating in colder conditions and producing much hotter water.

If the test conditions are different, comparing the headline COP figures alone can be misleading.

A more useful question is:

How will this heat pump perform under the conditions my home actually requires?

The heating water temperature required by the property can affect heat pump efficiency.

A conventional boiler system may have been designed around relatively high water temperatures.

A heat pump can often operate more efficiently when the heating system can provide the required comfort using lower water temperatures.

But the temperature cannot simply be reduced without considering the rest of the system.

Radiators and underfloor heating still need to provide enough heat to each room.

That is why flow temperature, radiator sizing and heat loss need to be considered together.

A radiator releases heat according to factors including its size and the temperature of the water flowing through it.

At a lower water temperature, the same radiator releases less heat.

That is why some existing radiators may need to be upgraded during a heat pump installation.

Others may already be suitable.

The installer should calculate the heat requirement of each room and determine whether the existing radiator can provide it at the proposed design temperature.

This is not simply about comfort.

It can also influence the conditions under which the heat pump operates.

Underfloor heating uses a large surface area to distribute heat.

This can allow comfortable room temperatures to be achieved using relatively low heating water temperatures.

That can create favourable operating conditions for a heat pump.

However, underfloor heating is not required for every heat pump installation.

A properly designed radiator system can also perform very well.

The right solution depends on the property.

Internal link: Renewable Heat Underfloor Heating

Before focusing on COP or SPF, the installer needs to understand how much heat your property actually requires.

That starts with heat loss.

Heat escapes through:

• Walls
• Windows
• Doors
• Roofs
• Floors
• Ventilation

Different rooms can have very different heating requirements.

A room by room heat loss calculation therefore helps determine:

• Heat pump size
• Radiator requirements
• Heating water temperature
• Pipework requirements
• Expected system performance

This is why Renewable Heat starts with a detailed Home Assessment before selecting equipment.

This is where the technical figures connect with current industry requirements.

MCS currently publishes a dedicated heat pump design standard, MIS 3005 D: 2025 Issue 2.0.

The standard places the focus on the design of the complete heat pump system rather than simply the product itself.

It requires installers operating within the MCS framework to comply with applicable legislation and current design requirements.

For homeowners, that reinforces an important point.

A heat pump installation should be based on proper calculations, appropriate system design and recognised standards.

COP and SCOP can help describe equipment.

But installation standards determine how that equipment should be incorporated into the home.

For Scottish homeowners, the Home Energy Scotland Grant and Loan provides current support towards eligible heat pump installations.

As of 2026, qualifying homeowners can receive grant funding of up to £7,500 towards a heat pump, with a rural uplift that can increase this to £9,000.

An optional interest free loan may also be available.

Importantly, the current scheme requires eligible renewable heating installations to use both:

An MCS certified installer

and

An MCS certified product

This matters in a COP and SPF article because it shows that efficiency figures are not the only consideration when choosing equipment.

The installation also needs to sit within recognised product and installer certification requirements where Scottish funding is being used.

Funding rules can change, so homeowners should always check current Home Energy Scotland guidance before committing to work.

Scotland’s New Build Heat Standard is another important part of the wider regulatory picture.

The standard prevents the use of direct emissions heating systems in new buildings that receive a building warrant from April 2024 onwards, subject to the current scope and amendments.

In practical terms, this means new Scottish buildings are moving away from heating systems that produce greenhouse gas emissions at the point of use.

Heat pumps are one of the technologies that can support this transition.

For homeowners reading about COP and SPF, this is relevant because it shows why heat pump performance is becoming an increasingly important part of Scottish building design.

The conversation is moving beyond whether heat pumps are a niche technology.

For new homes, low emission heating is becoming part of the regulatory environment.

Not in the same way.

The New Build Heat Standard is focused on new buildings within its scope.

Homeowners with existing properties should not read this article and assume they are legally required to remove their existing gas or oil boiler because of this standard.

Existing homes have a different policy and funding landscape.

For those properties, heat pump suitability still depends on the individual building, heating requirements and wider retrofit plans.

That distinction is important.

Imagine two properties using exactly the same heat pump model.

That does not mean they will achieve the same SPF.

Home A

Correct heat pump sizing

Suitable radiators

Appropriate pipework

Lower heating water temperatures

Good controls

Careful commissioning

Home B

Incorrect sizing

Undersized radiators

Restricted pipework

Higher heating water temperatures

Poor controls

Incomplete commissioning

The equipment may be identical.

The installed performance can be very different.

This is why heat pump performance is about the complete heating system.

A heat pump needs to be selected around the heating requirement of the property.

An undersized system may struggle to meet heating demand during colder design conditions.

An oversized system can create different problems, including unnecessary cost and potentially excessive cycling if its minimum output is too high for the property during milder conditions.

This is why heat pump sizing should not be based only on:

• Floor area
• Bedroom numbers
• Existing boiler output
• General assumptions

It should follow a detailed heat loss calculation.

Current Scottish funding requirements also reinforce this whole house approach.

Home Energy Scotland states that funded heat pump systems must provide the whole house heating and hot water requirements within the scheme criteria.

No.

COP describes efficiency.

Your energy bill depends on several additional factors.

These include:

• Property heat demand
• Seasonal heat pump performance
• Electricity tariff
• Indoor temperatures
• Hot water use
• Outdoor weather
• Household habits
• Solar PV generation
• Battery storage

A large home with an efficient heat pump may still use more electricity for heating than a much smaller property.

That does not necessarily mean the system is inefficient.

The larger property may simply require more useful heat.

This is why efficiency and demand need to be considered together.

Home A

Useful annual heating requirement:

10,000 kWh

SPF:

4

Approximate electricity required in this simplified example:

2,500 kWh

Home B

Useful annual heating requirement:

20,000 kWh

SPF:

4

Approximate electricity required:

5,000 kWh

Both systems have the same seasonal efficiency.

But Home B requires twice as much heat.

Its electricity requirement is therefore approximately twice as high in this simplified comparison.

Efficiency is only part of the cost equation.

Modern heat pump systems increasingly allow performance to be monitored.

Monitoring can help provide information about:

• Electricity consumption
• Heat output
• Temperatures
• Operating patterns
• Seasonal performance

This gives homeowners and engineers a more useful picture than a single COP figure from one particular day.

Renewable Heat can provide remote monitoring for suitable systems as part of ongoing service and support.

Several factors can affect SPF.

Higher Heating Water Temperatures

The heat pump generally has to work harder.

Incorrect Sizing

Poor sizing can affect operation throughout the heating season.

Unsuitable Radiators

Small radiators may require higher heating water temperatures.

Restricted Water Flow

Pipework and system design affect how heat moves around the property.

Poor Controls

Incorrect settings can prevent the system from operating as intended.

Hot Water

Domestic hot water often requires higher temperatures than space heating.

Outdoor Conditions

Air source heat pump efficiency changes as outdoor temperature changes.

Commissioning

The completed system needs to be tested, balanced and configured correctly.

These factors explain why the system design is just as important as the manufacturer’s headline efficiency number.

Weather compensation allows the heating system to adjust its water temperature according to outdoor conditions.

During mild weather, the property loses less heat.

The heating system may therefore be able to operate using a lower water temperature.

When outdoor conditions become colder, the required water temperature can increase.

The objective is to provide enough heat to maintain comfort without running at unnecessarily high temperatures throughout the year.

When configured correctly, this can support efficient operation.

Before choosing a heat pump, ask your installer to explain the expected performance.

Questions worth asking include:

What heat loss have you calculated?

Why have you chosen this heat pump size?

What design flow temperature are you using?

Have the radiators been assessed?

What seasonal performance do you expect?

What assumptions are behind that figure?

Does the installation comply with current MCS requirements?

How will the system be commissioned?

Can performance be monitored afterwards?

A good installer should be able to explain more than the number printed on the heat pump brochure.

This is the main point.

COP, SPF and SCOP are all useful.

But none should be viewed in isolation.

Real heat pump performance is created by the relationship between:

The property

The heat pump

The radiators or underfloor heating

The pipework

The controls

The hot water system

The weather

The commissioning

Current installation standards

That is why Renewable Heat takes a whole home approach.

Our Home Assessment looks at the property and heating requirements before equipment is recommended.

The objective is not simply to choose the product with the most impressive efficiency figure.

It is to design a heating system that gives the heat pump appropriate conditions in which to perform.

If you are comparing heat pumps, do not begin with COP alone.

Start by asking:

How much heat does my home require?

Then:

What heating water temperature will the system need?

Then:

Are the radiators or underfloor heating suitable?

Then:

What heat pump can meet those requirements efficiently?

Then:

How should the complete system be designed, installed and commissioned?

For Scottish homeowners, it is also worth checking whether current funding or building standards affect your project.

Renewable Heat has more than 20 years of experience designing and installing heat pump and home energy systems across Scotland.

We design air source and ground source heat pump systems around the individual property and can explain expected system performance before installation.

If you already have a heat pump and want to understand how it is performing, we can also discuss monitoring, servicing and system optimisation.

Call 0330 022 0480 or email sales@renewableheat.com to speak to the Renewable Heat team.