Solar PV and heat pumps go hand in glove. You are running an efficient heating system and generating the electricity to power it, which is why adding solar is often the logical next step in an eco-refurbishment once the heating is sorted.
According to the Energy Saving Trust, replacing an old gas boiler with a heat pump can save up to £530 a year, and adding solar PV can save a further £930 a year in London. That is close to £1,460 you are no longer handing to an energy company.
This article covers:
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The heat pump ready series A nine-part guide to preparing your home, produced with low-carbon homes architect Colin Usher. |
These two systems cost roughly the same and take up a similar amount of roof space, but they do very different jobs. Solar PV generates electricity, which can power anything in the house including the heat pump. Solar hot water only heats water.
| Solar PV | Solar hot water | |
|---|---|---|
| Typical cost | Around £6,500–£8,000 | Around £6,000 |
| Annual saving | Up to £930 | Around £210 |
| What it powers | Anything electrical, including the heat pump | Hot water only |
| Export income | Yes, via the Smart Export Guarantee | No |
| UK uptake | Almost 5% of homes | Around 0.5% of homes |
There is a seasonal mismatch too. Solar hot water generates most of its output in summer, when you need heating least. A heat pump does its work in winter. Solar PV is also less efficient in winter, but at least part of what it generates goes towards running the heat pump when you actually need it.
Given that solar PV can power large appliances, an EV, home entertainment and heating, it is no surprise the uptake gap is so wide.
Have solar PV installed by an MCS or Flexi-Orb accredited company. Both certification bodies ensure work is done to a high standard, and certification matters for five practical reasons:
So while MCS makes sense if you are using one company for both the heat pump and the solar, do not discount a Flexi-Orb installer for solar work — their ongoing quality control is more stringent.
Generation is heavily seasonal. A 4kWp system in London generates roughly:
Between 60% and 70% of annual generation falls between April and September. At the current capped rate that is worth around 22p a day in December against £1.54 a day in June — though much of the summer generation is exported rather than used, so those figures do not translate directly into savings.
There is more than a 35% difference in annual generation between the south of England and northern Scotland, purely because of latitude.
That said, solar saves money anywhere in the UK. Germany has similar or lower irradiance than southern England and is one of the world's largest solar markets.
Regional generation data: Switch Together
South-facing is ideal in the UK, but the penalty for other orientations is smaller than most people assume.
| Roof direction | Output vs south-facing |
|---|---|
| South | 100% |
| South-east or south-west | 95–97% — a loss of only 3–5% |
| East or west | 80–85% — still well worth installing |
| North | Around 50–60% — rarely recommended |
The east-west case deserves a second look. An east-west split array gives a wider generation curve rather than a midday spike: east panels produce through the morning, west panels through the late afternoon and into the evening peak. For a household on a time-of-use tariff or running a battery, that often matches demand better than a south-facing array producing everything at noon when nobody is home.
The optimum is 30° to 40°. Most UK roofs sit between 25° and 45°, which is fine. Pitches above 50° or below 20° are less efficient and are one of the situations where micro-inverters help.
This is the point that gets least attention and deserves the most. Partial shading from a tree, chimney or neighbouring building can cut a panel's output by 20% to 50%. A west-facing roof in clear sun will outperform a south-facing roof with a tree blocking the afternoon.
Any reputable installer will assess shading as part of the site survey.
An inverter converts the direct current from your panels into the alternating current your home uses. There are two types, and the choice depends on your roof.
A string inverter connects to all the panels in an array. Because the panels are wired in series, output is limited by the weakest performing panel — so if one is shaded, the whole string suffers.
Micro-inverters use one unit per panel, so each panel produces independently. They are more durable and more expensive.
String inverters are fine for a typical south-facing array with no shading. Micro-inverters are worth the extra where you have:
Building regulations apply to every solar PV installation without exception, and will be signed off by your certified installer. Three parts are relevant:
These are a legal requirement and cannot be short-cut.
In most cases no, because solar falls under permitted development rights. There are exceptions worth checking:
A good installer will advise you, but a little research of your own — checking your deeds and asking the council — flags any issues well ahead of time.
Your array generates whatever it can convert from sunlight, regardless of how much you happen to be using. The Smart Export Guarantee (SEG) means you are paid for what you do not use and send to the grid.
Rates currently range from roughly 5p to 20p per kWh, with some time-of-use export tariffs paying more at peak times. As soon as your system is commissioned, shop around for the best rate available.
You do not have to export to the same company you buy from. If you do, they simply deduct the export payment from your bill.
Time-of-use tariffs charge more at peak times and less off-peak. With solar and a heat pump, that might mean heating your hot water cylinder while generation is at its highest.
If you are home during the day, run the washing machine, dishwasher and EV charging while the sun is doing the work. Time-of-use export rates are also available, letting you export when payments are highest.
The last question is whether to add a battery or a V2X system, and generally the answer is yes — particularly given where the technology is heading.
If you spend daylight hours at home and run heavy appliances then, you are already consuming much of what you generate and the battery adds less. But in winter, on a time-of-use tariff, you can still store cheap off-peak electricity to cover expensive peak periods.
If you have a V2X-compatible EV at home during the day, a bidirectional charger can cost a fraction of a home battery while offering far greater capacity. Some batteries and bidirectional chargers can also power your home during a power cut, though not all installations include that.
Our guide to home batteries covers sizing, tariffs and the V2X comparison in detail.
No. Heat pumps run perfectly well on grid electricity. Solar panels simply reduce how much electricity you need to buy, lowering running costs. The two work well together, but neither depends on the other.
South-facing generates the most in the UK. South-east and south-west lose only 3% to 5%. East and west produce 80% to 85% of a south-facing array, which is still well worth installing. North-facing produces around half and is rarely recommended.
Yes. An east-west split produces 80% to 85% of a south-facing array, but spreads generation across morning and late afternoon rather than peaking at midday. For households on time-of-use tariffs or with a battery, that often matches demand better than a south-facing system.
Yes. Certification is normally required to receive Smart Export Guarantee payments, and matters for building regulations sign-off, home insurance and conveyancing. MCS certification is what qualifies a heat pump installation for the Boiler Upgrade Scheme.
Usually not, as most domestic installations fall under permitted development. Listed buildings need listed building consent from your local planning authority, and conservation areas or homes under an Article 4 Direction may require permission.
It depends on when you use electricity. If you are out during the day, a battery stores surplus generation for evening use rather than exporting it cheaply. If you are home all day you will use much of it directly and benefit less, though a battery still helps in winter on a time-of-use tariff.
For most homes, no. Both cost roughly the same and use similar roof space, but solar hot water saves around £210 a year against up to £930 for solar PV. Solar PV also powers the heat pump and everything else electrical, and earns export income.
A heat pump is one of the biggest steps you can take to cut your home's carbon emissions. Solar PV is one of the best ways to cut its running costs. Neither is essential to the other, but together they form one of the most effective home energy combinations available.
Do not rule your roof out too early. Only a north-facing roof is genuinely marginal, and shading usually matters more than direction. Choose a certified installer, understand what your roof can realistically produce, and make the most of export tariffs and storage where they suit how you live.
Do that and you will lower your bills while making your home considerably more resilient to future energy price rises.
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That completes the series Start again from 1. How to Make Your Home Heat Pump Ready, or revisit 8. Home batteries. Whatever you decide about heating, making sure you are on the right electricity tariff costs nothing and takes a few minutes. |
Produced with Colin Usher, low-carbon homes architect. Last updated: 3 August 2026.
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