The best angle for solar panels in the UK is 37 to 40 degrees from horizontal on a south facing roof, depending on how far north you live. On a pitched roof, though, the honest answer is that your existing angle is almost certainly fine, because everything between 30 and 45 degrees lands within 2 per cent of the peak. That is not a rule of thumb. It is what the MCS irradiance tables say when you open them and read the cells.
Those tables are the ones your installer has to use. Every MCS certified quote in the country estimates your generation with the same formula, and the angle of your roof is one of the three numbers that goes into it. So the question "what angle should my panels be" has a documented answer rather than a sales answer, and you can check it against the quote in front of you.
Below is the answer by region, the arithmetic on what a non-ideal pitch actually costs, and the one situation where the angle is the entire decision rather than a rounding error.
Ask each installer for the roof pitch in degrees that they used in your estimate. It is a required field on every MCS performance estimate, so any certified installer already has it written down.
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Between 37 and 40 degrees from horizontal, facing due south, with the exact figure rising the further north you go. MCS publishes a spreadsheet of kWh per kWp values, called Kk values, covering 25 UK postcode zones at every single degree of pitch. The table below is read directly from that file, taking the due south column for each zone.
| Zone | Best pitch band | Kk at peak | At 30° | At 45° |
|---|---|---|---|---|
| London | 37–40° | 985 | 977 | 980 |
| Plymouth | 38–40° | 1,093 | 1,082 | 1,088 |
| Cardiff | 37–39° | 950 | 943 | 945 |
| Birmingham | 37–40° | 937 | 929 | 933 |
| Manchester | 37–40° | 866 | 859 | 862 |
| Belfast | 39–40° | 847 | 838 | 844 |
| Glasgow | 39–40° | 835 | 826 | 832 |
| Aberdeen | 40–45° | 877 | 862 | 877 |
Kk is the number of kilowatt hours a system is expected to produce per kilowatt peak of panel, per year, before shading. Source: the MCS Irradiance Datasets spreadsheet, downloaded and read on 15 September 2026. Figures are for a due south array and are rounded as MCS publishes them.
Notice that the peak is not a single degree but a plateau several degrees wide. In London the tables return the identical figure of 985 for anything between 37 and 40 degrees. In Aberdeen the plateau runs from 40 all the way to 45. That alone tells you how blunt an instrument roof pitch is.
Two other things jump out. The optimum creeps north with latitude, from 37 degrees in London to 40 in Aberdeen, because the sun sits lower in the sky and a steeper panel meets it more squarely. And the gap between the peak and a bog standard 30 or 45 degree roof is tiny in every single zone.
What a "wrong" pitch actually costs you on a pitched roof
On a typical 4.5kWp system in London, moving from a 30 degree roof to the theoretical best 37 degrees would gain about 36 kilowatt hours a year, worth roughly nine pounds. That is the whole prize, and it is why no reputable installer will suggest altering your roof to chase it.
Here is the arithmetic in full, using the standard MCS method. The Energy Saving Trust puts the average UK domestic system at 4.5kWp, so:
- At 30 degrees: 4.5 × 977 = 4,397 kWh a year
- At 37 degrees: 4.5 × 985 = 4,433 kWh a year
- Difference: 36 kWh a year
From 1 October 2026 the Ofgem price cap sets electricity at 26.32p per kWh for a typical Direct Debit customer, up from 26.11p over the summer. Even if you used every one of those 36 units yourself and displaced grid electricity at the full cap rate, you would be about nine pounds and fifty pence a year better off. A 45 degree roof does slightly better again, losing only about six pounds a year against the peak.
Scaffolding alone on a two storey house costs considerably more than that over the panels' 25 year life. So the practical rule is simple: if your roof pitch is anywhere between 30 and 45 degrees, the angle is settled and there is nothing to optimise. What is worth your attention instead is the direction your roof faces and whether anything shades it, which are the two site factors that genuinely move the number.
Pitch swings your yield by under 2 per cent across normal roofs. Location swings it by 26 per cent: the same panels rated at 1,093 Kk in Plymouth are rated 866 in Manchester. You cannot move your house, and you should not re-pitch your roof. Both facts come from the same spreadsheet.
On a flat roof, the angle is the entire decision
This is the one case where tilt is worth real money. Laying panels flat in London gives a Kk of 828. Tilting the same panels to 37 degrees facing south gives 985, a gain of about 706 kWh a year on a 4.5kWp system, or roughly 186 pounds at the October 2026 cap rate.
The Energy Saving Trust describes the standard practice plainly: panels on flat roofs "are normally tilted up to help maximise energy production". It also flags what that costs you structurally. The mounting must not disturb the roof covering, so systems are usually weighted down with ballast rather than fixed through the membrane, and the roof then has to carry the extra load.
So on a flat roof you are making a genuine choice, not accepting an inherited one, and the choice is worth about two hundred pounds a year. Our guide to solar panels on a flat roof covers the ballast and structural side in detail.
The east west trap that catches flat roof installs
If a flat roof array is going to face east or west rather than south, the MCS tables say you are better off leaving the panels flat than tilting them up. This is the least intuitive thing in the dataset and it is worth checking against your quote.
Read across the London sheet by orientation and the best pitch moves:
| Orientation | Best pitch | Kk at best pitch | Kk if tilted to 35° |
|---|---|---|---|
| Due south (0°) | 37–40° | 985 | 984 |
| South east or south west (45°) | 33–36° | 927 | 927 |
| Due east or due west (90°) | 0°, flat | 828 | 783 |
| Near north (175°) | 0°, flat | 828 | 540 |
The pattern is that tilting only helps while you are pointing at the sun's arc. Turn the array away from south and the optimum flattens out, because a horizontal panel is neutral about direction and collects light from wherever it comes. By due east or west, a 35 degree tilt has become a 45 Kk penalty against simply laying the panels flat, which on a 4.5kWp array is about 203 kWh or 53 pounds a year thrown away.
On a pitched roof this is academic, because you cannot choose. On a flat roof, where the installer picks both the tilt and the direction, it is a question worth asking out loud.
The 15 degree rule that argues against laying panels flat
Panels need a tilt of at least 15 degrees for British rain to keep them clean. The Energy Saving Trust states it directly: "In the UK, rain will clean your panels if they're tilted at 15 degrees or more."
That matters because it pulls against the previous section. If the tables say a truly flat array is optimal for an east west flat roof, the maintenance reality says a completely horizontal panel will accumulate dirt that rain does not shift, and you will be paying someone to clean a roof you would otherwise never touch.
The sensible middle ground on a flat roof is a shallow tilt of around 15 degrees. In London that is a Kk of 924 facing south, well above the 828 you get lying flat, and it keeps the panels self cleaning. Our guide to solar panel maintenance covers what cleaning actually costs if you do end up needing it.
What planning rules let you do with the angle
In England, panels on a pitched roof must not project more than 200mm from the roof slope, which effectively rules out tilting them off their existing pitch. That single limit is why nobody is fitting tilt frames to sloped British roofs, whatever the irradiance tables might prefer.
The Planning Portal sets out the permitted development limits for a house in England. On a pitched roof, panels "should not be installed above the highest part of the roof (excluding the chimney) and should project no more than 200mm from the roof slope". On a flat roof, the highest part of the equipment "cannot be more than 600mm higher than the highest part of the roof", which is what caps how steeply a flat roof array can be tilted in practice.
Worth knowing: the England permitted development right for solar was updated on 27 August 2026, and there is a 12 month transitional period running to 27 August 2027 during which you can follow either the old rules or the new ones. The 200mm pitched roof limit and the 600mm flat roof limit survive in both versions. Source: Planning Portal, solar equipment mounted on a house, read on 15 September 2026. The rules differ in Wales, Scotland and Northern Ireland, and our guide to permitted development for solar panels takes each nation separately.
How to check your quote used your real roof pitch
Every MCS certified installer has to give you a performance estimate before you sign, and the roof pitch in degrees is a named field on it. That turns this from something you take on trust into a document you can read.
The Solar PV Standard, MIS 3002 Issue 5.0, sets out the method your installer must follow. The six steps are: establish the array rating in kWp, determine the postcode region, determine the array pitch, determine the array orientation, look up the Kk value from the location specific table, and determine the shading factor. The output is then calculated as:
Annual AC output (kWh) = kWp × Kk × SF
On pitch specifically, the standard says the value "is to be measured or determined from plan", that it is expressed as degrees from horizontal where "0° represents a horizontal array; 90° represents a vertical array", and that it is rounded to the nearest 1 degree. So there is a real number, measured from your roof or taken off a drawing, sitting behind the generation figure on your quote.
Three questions are worth asking:
- What pitch in degrees did you use? If it is a round 30 or 40 on every quote you have collected, at least one of them has guessed.
- Which postcode zone and Kk value? MCS publishes 25 zone tables, and the figure should match your area. Plymouth and Manchester differ by over 200 kWh per kWp.
- What shading factor did you apply? MIS 3002 calls inclination, orientation and shading "the three main site factors", and notes that while drawings or photos are fine for working out inclination and orientation, "an accurate estimation of any shade effects will typically require a site visit".
That last point is the one that separates a real survey from a desk estimate. Pitch and direction can be read off a map. Shade cannot, which is why optimisers get sold on the back of assumptions rather than measurements. If you want to compare how different installers handle it, our guide to choosing a solar installer covers what to look for.
Where the MCS numbers come from
One detail worth knowing, because it explains why MCS estimates tend to look conservative next to manufacturer brochures. MIS 3002 states that the Kk data "has been provided by the European Commission, Joint Research Centre", that it is "drawn from the Climate-SAF-PVGIS dataset", and then adds four words that do a lot of work: "and multiplied by 0.8".
In other words, every generation figure on every MCS quote in Britain has a 20 per cent haircut baked into it before anyone touches your roof. That is deliberate conservatism covering real world losses, and it is a good reason to treat a quote promising numbers well above the MCS estimate with suspicion. It also means the figures in this article are already the cautious version.
If your roof is pitched between 30 and 45 degrees, your angle is fine and there is nothing to buy. If your roof is flat, the tilt is worth around 186 pounds a year and deserves a proper conversation, with 15 degrees as the floor and south as the target.
Best angle for solar panels: frequently asked questions
Between 37 and 40 degrees from horizontal on a south facing array, rising the further north you are. The MCS irradiance tables put the start of the peak at 37 degrees for London, Cardiff, Birmingham and Manchester, 38 for Plymouth, 39 for Glasgow and Belfast, and 40 for Aberdeen. The peak is a plateau rather than a point: London returns an identical figure anywhere from 37 to 40 degrees. The optimum steepens with latitude because the sun sits lower in the sky.
Very little, on a normal pitched roof. Across the 30 to 45 degree band that covers almost every British house, the MCS tables show a spread of only 7 to 15 kWh per kWp depending on region, which is under 2 per cent. On a 4.5kWp system in London, the gap between a 30 degree roof and the ideal 37 degrees is about 36 kWh a year, worth roughly nine pounds at the October 2026 price cap rate.
Yes, if the array will face south. Laying panels flat in London gives a Kk of 828 against 985 at a 37 degree south facing tilt, a difference of about 706 kWh a year on a 4.5kWp system, or roughly 186 pounds. The Energy Saving Trust notes panels on flat roofs "are normally tilted up to help maximise energy production", usually on ballasted frames so the roof covering is not pierced, which means the roof must carry the extra weight.
A steeper angle does favour the low winter sun, which is why the optimum pitch rises as you go north. But the MCS Kk tables are annual figures, and over a full year the best compromise in the UK still lands at 37 to 40 degrees. Chasing winter output with a much steeper array costs you more in summer than it gains in December, and the UK generates the bulk of its solar electricity between April and September.
Close to flat, according to the MCS tables, which is the opposite of the usual advice. For a due east or due west array in London the tables peak at 0 degrees with a Kk of 828, while tilting to 35 degrees drops it to 783. Tilting only helps while the array points towards the sun's arc. In practice a shallow tilt of around 15 degrees is the sensible compromise, because the Energy Saving Trust says rain will only self clean panels tilted at 15 degrees or more.
Not within permitted development in England. The Planning Portal states that on a pitched roof panels "should not be installed above the highest part of the roof (excluding the chimney) and should project no more than 200mm from the roof slope", and a tilt frame large enough to change the angle meaningfully would breach that 200mm limit. The England permitted development right was updated on 27 August 2026 with a transitional period to 27 August 2027, and the 200mm limit applies under both the old and new versions.
Ask for the MCS performance estimate, where the roof pitch in degrees is a required field. MIS 3002 Issue 5.0 requires the pitch to be measured or determined from plan, expressed as degrees from horizontal and rounded to the nearest 1 degree, then used in the calculation Annual AC output (kWh) = kWp x Kk x SF. If several quotes all show the same round number, at least one installer has estimated rather than measured.
No. Direction matters considerably more. The Energy Saving Trust puts an east or west facing roof at around 15 to 20 per cent less output than due south, while pitch moves the figure by under 2 per cent across the range of normal UK roofs. Location matters more still: the MCS tables rate Plymouth at 1,093 Kk against 866 for Manchester, a difference of 26 per cent.
Because MCS applies a deliberate 20 per cent reduction. MIS 3002 states the Kk data was provided by the European Commission's Joint Research Centre, is drawn from the Climate-SAF-PVGIS dataset, "and multiplied by 0.8". Every MCS quote in Britain carries that haircut before shading is even considered, so a quote promising substantially more than the MCS estimate is worth questioning.