M&E Contrax Resources

Solar Panels and a Heat Pump Together

Resource Highlights:

A heat pump increases your household electricity consumption significantly, typically by 3,000 to 5,000 kWh per year. Solar panels offset a meaningful portion of that consumption with electricity you generate yourself, reducing the running cost of the heat pump directly.

The two technologies work best together when the solar system is sized with the heat pump’s electricity demand in mind, not just the household’s baseline consumption.

Solar and heat pumps can be installed in either order, or at the same time. The right sequence depends on your circumstances, your budget, and whether your current heating system has failed or is still working.

The combined financial case is stronger than either technology alone. Solar reduces heat pump running costs for the life of the system, and the heat pump increases how much of your solar generation you consume yourself rather than exporting at a lower rate. Each technology improves the return on the other.

Two technologies that make each other work harder

A heat pump runs on electricity. Solar panels generate it. Putting the two together is one of the most effective things you can do to reduce both your energy bills and your reliance on the grid, because each technology directly improves the financial return on the other.

At M&E Contrax Renewables, we design and install combined solar and heat pump systems for homes and businesses across Devon and the South West. Because we hold MCS accreditation for both technologies and carry out all electrical installation work with our in-house NICEIC-accredited engineers, we can survey, design, and install the whole system under one roof rather than coordinating between separate contractors.

We work with a range of leading heat pump and solar products including Vaillant, Samsung, and Daikin heat pumps alongside solar panel systems with battery storage from Tesla, Fox, GivEnergy, and others, and we size every system around your property’s actual consumption rather than a generic template.

Why these two technologies work well together

A heat pump and a solar panel system each make a reasonable financial case in isolation. Together, they interact in ways that make both investments more valuable.

The reason comes down to electricity. A heat pump is highly efficient at converting electricity into heat, typically producing three to four units of heat for every unit of electricity it consumes. But it runs on electricity, which costs more per unit than the gas or oil it is replacing. Solar panels generate electricity from daylight at no ongoing cost. When that solar electricity powers the heat pump, the effective cost of the heat it produces falls significantly.

At the same time, a heat pump increases your household electricity consumption, which means more of your solar generation gets used on site rather than exported to the grid. Self-consumption is where solar returns most value. The heat pump gives your solar system more demand to meet, improving self-consumption and the overall financial return from the panels.

The two technologies also have complementary seasonal profiles. Solar panels produce most strongly in spring, summer, and early autumn. Heat pumps work most efficiently at mild outdoor temperatures, which in the UK means spring and autumn. The periods of best solar generation and best heat pump efficiency overlap meaningfully, even if winter heating demand and limited winter solar output mean grid electricity will always be needed for a portion of the year.

How solar reduces heat pump running costs

A heat pump installed without solar draws all its electricity from the grid. A heat pump paired with solar draws some of that electricity from panels instead, at no ongoing cost per unit.

The scale of this reduction depends on system size, household occupancy pattern, and whether a battery is included.

Without battery storage, a 5kWp solar system on a Devon property can be expected to offset somewhere in the region of 800 to 1,200 kWh of heat pump electricity demand per year. This comes from the direct overlap between solar generation periods and times when the heat pump is running, particularly in spring and autumn when both generation and heating demand are present simultaneously, and in summer when the heat pump is running primarily for domestic hot water rather than space heating.

With a 10kWh battery added to the system, that offset can rise to 1,500 to 2,000 kWh per year, because solar electricity generated at midday can be stored and used in the evening when the heat pump is running to maintain temperature as the day cools.

There is a third route that is worth understanding: smart hot water control. Devices such as the myenergi Eddi divert surplus solar generation that would otherwise be exported to the grid into the hot water immersion element in the heat pump’s cylinder. When solar generation is high and household demand is low, the Eddi diverts that surplus into the cylinder, heating water for free. At lower generation levels it trickle-charges rather than exporting. The hot water cylinder becomes a form of thermal storage, absorbing solar energy that would otherwise leave the property at the export rate. This is a relatively modest addition to the system but can meaningfully improve overall performance.

How the heat pump improves solar returns

A household without a heat pump and without an EV charger often struggles to self-consume more than 30 to 40% of what its solar panels generate. The middle of the day, when panels produce most strongly, is often the period of lowest household demand. Surplus generation flows to the grid at the export rate.

A heat pump changes this. Space heating and domestic hot water between them represent a large and relatively flexible load. A well-controlled heat pump can be programmed to run its heating cycles and heat its cylinder during the hours when solar generation is highest, absorbing solar electricity that would otherwise be exported. This is not always straightforward to optimise, and it depends on the heat pump’s controls and your installer’s configuration, but the principle is sound and the impact on self-consumption can be significant.

In winter, when solar generation is at its lowest, the heat pump’s demand for electricity means that almost everything the panels produce is consumed on site. Research into combined heat pump and solar systems has found self-consumption rates rising to 94 to 100% in winter months, because supply and demand align almost perfectly. This is the inverse of summer, when solar surplus is high and space heating demand is low.

The net effect across the year is a higher average self-consumption rate than a solar-only household would achieve, which improves the financial return from the panels.

What order should you install them in?

This is the question we are most often asked by homeowners who want both but cannot or prefer not to do both at the same time.

There is no single right answer, but the following framework covers most situations.

Install solar first if:

Your current heating system is working and not approaching end of life. Solar has a shorter and more straightforward payback period than a heat pump and involves less disruption to the property. Installing solar first generates savings from day one while you plan and fund the heat pump. When the heat pump is later added, the solar system is already sized and generating, and the combined financial case immediately improves.

You are in a property that may need fabric improvements before a heat pump is worth installing. Loft insulation, draught-proofing, and possible radiator upgrades are best assessed and carried out before a heat pump design is finalised. Solar can be installed and generating during that process.

You have a limited budget at this point and want to start somewhere practical. Solar is the lower-disruption, faster-payback first step.

Install the heat pump first if:

Your boiler has failed or is unreliable. Replacing it with a heat pump while the BUS grant is available makes more sense than replacing it with another gas or oil boiler and then fitting a heat pump a few years later. The grant is not guaranteed to remain at its current level indefinitely.

You are undertaking a significant renovation and the disruption of heat pump installation, including possible radiator upgrades and a new cylinder, is manageable within the wider project. Adding solar can follow once the heating system is settled.

You are in a rural off-gas property where oil heating costs are high and the BUS grant makes the heat pump financially compelling right now.

Install both at the same time if:

You are undertaking a full home retrofit or a new installation and want to design the system as an integrated whole. This approach allows the solar system to be sized with the heat pump’s electricity demand already accounted for, which is the ideal starting point. It avoids the risk of undersizing solar relative to total household consumption. It also means a single survey, a single installation mobilisation, and a single set of commissioning checks.

Doing both at once does not necessarily mean the same week. It means designing both together so that the solar system spec reflects the whole picture.

Sizing solar when you have a heat pump

A household without a heat pump typically uses between 3,000 and 4,500 kWh of electricity per year. A standard domestic solar installation of 3.5 to 4kWp is often designed around that baseline.

A heat pump adds typically 3,000 to 5,000 kWh of annual electricity demand on top of that figure, depending on the size of the property, the insulation level, and how efficiently the system is designed and operated. A household with a heat pump may therefore have a total electricity demand of 6,000 to 9,000 kWh per year.

Sizing solar for a home with a heat pump on the basis of pre-heat-pump consumption will result in a system that is too small relative to total demand. The right approach is to assess the full electricity picture, including the heat pump’s projected consumption, before specifying the solar system.

As a general guide:

A household with a heat pump but no EV charger typically benefits from a solar system in the 5 to 6kWp range, combined with a battery of 10kWh or more.

A household with both a heat pump and an EV charger is looking at 6kWp or larger, with a battery of 10 to 13kWh.

These are starting points rather than precise recommendations. The right size for your property depends on your roof, your consumption profile, your occupancy pattern, and how aggressively you want to offset grid electricity. A proper combined survey and system design is the only way to get to a reliable figure.

The role of battery storage in a combined system

Battery storage is more valuable in a home with a heat pump than in a home without one, for two reasons.

First, the heat pump runs in the evening as well as during the day. Without a battery, solar electricity generated at midday cannot be stored for the evening heat pump cycle and is exported instead. A battery bridges that gap.

Second, the heat pump’s electricity demand is large enough to absorb a meaningfully sized battery on a regular basis. A household without a heat pump may find that a 10kWh battery sits partially empty much of the time and the payback case is weaker. A household with a heat pump has enough evening and overnight electricity demand to make good use of that stored capacity consistently.

The practical recommendation for most homes combining solar and a heat pump is a battery in the 10kWh range, paired with a solar system sized as described above. This combination typically increases annual solar self-consumption from around 40 to 50% without storage to 70 to 80% with it, which materially changes the running cost calculation.

Grants available for each technology

One of the practical advantages of planning both technologies together is being able to map the available grants across the whole project from the outset.

Solar panels: 0% VAT on all domestic solar and battery storage installations, confirmed until at least March 2027. No grant for most owner-occupiers, but the Warm Homes Local Grant can fund a complete solar and battery installation for eligible lower-income households with poor EPC ratings.

Heat pumps: The Boiler Upgrade Scheme provides £7,500 towards an air source heat pump for homeowners in England and Wales replacing a fossil fuel system. The grant is applied by the installer and deducted from the installation cost. No income test applies.

Both together: BUS and solar VAT relief can be used for the same household. They cover different technologies and there is no conflict between them. If you are eligible for the Warm Homes Local Grant, this covers both solar and heat pump in a single funded package for qualifying households.

Our full guide to the Warm Homes Plan and our guide to the Boiler Upgrade Scheme cover each of these in more detail.

Last reviewed: April 2026. Grant amounts, VAT relief, and tariff rates are subject to change. Always verify current figures at the time of installation.

FAQs

Yes. If you already have solar panels and are adding a heat pump, the existing system will contribute to the heat pump’s electricity supply. It is worth having an installer review whether the existing solar system is appropriately sized for the combined demand, and whether a battery retrofit would improve performance. See our home solar battery storage guide for more on retrofitting storage.

No. Solar panels, inverters, batteries, and heat pumps from different manufacturers work together without compatibility issues at the system level. Smart controls and energy management systems can integrate different components, though some features work better within ecosystems of compatible products. Your installer can advise on the best combination for your property.

No. In summer, space heating demand falls significantly and the heat pump primarily runs for domestic hot water. Solar generation in Devon in summer is high, and a heat pump alone will not absorb all of it. A battery stores surplus for evening use, and a solar diverter can direct further surplus into the hot water cylinder. Even with both, some summer generation will typically be exported. This is normal and the export earns SEG income.

No. The BUS grant is applied on the heat pump installation, regardless of whether solar is being installed at the same time. The two installations can proceed on the same project without affecting grant eligibility for the heat pump.

What a combined survey covers

When we survey a property for a combined solar and heat pump installation, the scope is broader than for either technology alone. The key elements are:

Heat loss calculation. The starting point for heat pump design. Room-by-room assessment of how much heat the building loses at the design temperature, which determines what output the heat pump needs to provide and at what flow temperature.

Electricity consumption assessment. Current household consumption from bills or smart meter data, projected consumption with the heat pump added, and the solar system size needed to offset a meaningful proportion of total demand.

Roof assessment. Orientation, pitch, shading, and condition, with the solar system designed around the total consumption picture rather than pre-heat-pump usage.

Heat emitter assessment. Whether existing radiators can deliver enough heat at the lower flow temperatures a heat pump operates at, or whether upgrades are needed.

Hot water cylinder. The capacity and configuration needed for both the heat pump and, where relevant, solar diversion.

Outdoor unit placement. Space, access, and noise considerations for the heat pump unit.

Battery and controls. Whether a battery is appropriate, what capacity suits the combined system, and how controls will be configured to maximise solar self-consumption across both household electricity and heat pump operation.

A survey for a combined system takes longer than a survey for one technology in isolation, but it produces a coherent design for the whole system rather than two separate specifications that may not be optimised for each other.

Talk to M&E Contrax

We design and install combined solar and heat pump systems for homes and businesses across Devon and the South West. Whether you are planning both technologies together or adding one to an existing installation, we carry out a single integrated survey covering the full picture before recommending anything.

Both M&E Contrax and M&E Contrax Renewables hold MCS accreditation, which means we can survey, design, install, and register both technologies under one roof.

MCS Accredited | NICEIC Approved | Newton Abbot, Devon | 24/7 aftercare