For the most electricity over a year, point solar panels due south and tilt them at about 35 to 40 degrees. That is the textbook answer, and it is correct. But most UK roofs were not built to face south, and the good news is you lose far less by facing east or west than people fear, often only around 15 to 20 per cent. In many homes the smarter question is not "how do I squeeze out the last few per cent", but "which layout puts power on the roof when I am actually at home to use it". Get that right and a supposedly imperfect roof can save you more real money than a perfect one.
The short answer. South-facing at roughly 35 to 40 degrees gives the highest annual output in the UK. South-east or south-west costs you very little, perhaps a few per cent. Due east or due west typically drops output by around 15 to 20 per cent, which is a modest price for a broader spread of generation across the day. North-facing is the one to avoid where you can. Angle matters less than direction: anything from about 20 to 50 degrees is within a whisker of ideal, so a standard pitched roof is almost always fine as it is.
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Why south wins, and by how much
In the northern hemisphere the sun tracks across the southern half of the sky, so a south-facing surface catches the most direct sunlight over the course of a day and a year. A due-south array in the UK is the benchmark against which everything else is measured, and it produces the largest annual total of kilowatt hours for a given number of panels.
What surprises people is how gentle the penalty is for pointing elsewhere. Rotate the array to south-east or south-west and you shed only a small slice, in the region of 3 to 6 per cent. That is because the sun spends a long time in the broadly southern sky, so being a little off due south still catches most of it. Only when you swing all the way round to due east or due west does the drop become noticeable, and even then it is around 15 to 20 per cent, not the half that some people assume.
| Roof direction | Rough annual output vs south |
|---|---|
| Due south | 100% (the benchmark) |
| South-east / south-west | ~94 to 97% |
| Due east / due west | ~80 to 85% |
| North-east / north-west | ~65 to 75% |
| Due north | ~55 to 65% (avoid where possible) |
Illustrative UK figures for a typical roof pitch; exact numbers vary with location and tilt.
The ideal tilt, and why your roof is probably fine
For the best annual yield in the UK, an angle of about 35 to 40 degrees from horizontal is close to ideal. That happens to sit near the average pitch of a British house roof, which is why most installations simply follow the existing roofline and get within a few per cent of optimal without any special mounting.
Tilt is forgiving. Anywhere from roughly 20 to 50 degrees loses only a small amount against the ideal, so worrying about a degree or two is pointless. The angle does change the shape of your year, though. A steeper tilt, say 45 to 60 degrees, catches the low winter sun a little better and sheds rain and light snow more readily, while a shallower tilt favours the high summer sun. Since the UK makes far more solar power in summer than winter regardless, most people are best served by the standard roof pitch and should not pay for a custom frame to chase small gains.
A flat roof is the one case where tilt is a real decision, because the panels have to be raised on frames anyway. There, angling them up to around 10 to 20 degrees is common, kept shallow so rows do not shade each other and so wind loading on the frames stays manageable.
East-west split: less peak, more usable power
Here is where the textbook answer and the sensible answer part company. An east-west split, panels on both slopes of a roof rather than all on one south face, produces a lower single peak but a broader, flatter curve: a burst in the morning from the east side and another in the late afternoon from the west. The total over the year is a bit lower than an all-south array, but the shape can suit a household far better.
Why does that matter for your pocket? Because the power you use in your own home is worth the full unit rate you would otherwise pay, around 26p per kWh as an example, whereas power exported to the grid earns you only the Smart Export Guarantee rate, often nearer 15p. A tall midday peak from a south array frequently overshoots what you can use at lunchtime, so a chunk gets exported cheaply. An east-west spread lines up better with breakfast and evening demand, so more of what you make is used at home. If you are out all day and only home mornings and evenings, an east-west roof can quietly beat a south one on money saved, even while making slightly fewer units.
Matching the array to your day
Follow that logic and the best layout depends on when you are home. A few honest cases:
- Home during the day (working from home, retired, young family): a south or south-west array suits you, because you can actually use the big midday and afternoon output.
- Out at work weekdays, home mornings and evenings: an east-west split, or a west-leaning array, puts more generation into the hours you are there, so more is self-used rather than exported.
- Heavy evening use and a battery: direction matters less, because a home battery soaks up the daytime surplus and hands it back after dark. With storage, chasing peak generation is less important than total generation.
You can push self-consumption higher whatever your roof by running the dishwasher, washing machine and other heavy loads in daylight. To see what each appliance actually draws so you know what your panels can cover, the running-cost calculator prices anything in pennies per use.
What shade really costs
Direction and angle are worth little if a chimney, a tree or a neighbour's roof throws shadow across the panels during the productive hours. Shading hurts more than its size suggests, because panels wired in a string can drag each other down: one shaded panel can pull the whole string's output below what the sunny panels alone would give. A tall south array in shade can easily underperform a clear east-facing one.
Two things help. First, honest assessment before you commit: watch where shadows fall across the roof through the day and across the seasons, remembering the winter sun sits very low and long shadows reach further. Second, hardware that limits the damage, such as power optimisers or microinverters, which let each panel work independently so a shaded one no longer throttles its neighbours. They add cost, so they earn their place mainly where some shading is unavoidable. If your roof is truly clear, standard string wiring is fine.
Dirt, snow and keeping panels producing
A steeper tilt has a side benefit: rain runs off more freely and takes dust, pollen and grime with it, so panels largely self-clean. On a shallow roof, dirt lingers longer and a light film can shave a few per cent off output over time. In most of the UK, rainfall does the cleaning and you rarely need to intervene, though a build-up of moss, leaves or bird mess near the lower edge is worth clearing. Snow slides off a steep panel quickly once the sun hits it; on a shallow array it can sit longer, but UK snow cover is brief enough that the annual loss is tiny. There is more on upkeep and expected lifespan in how long solar panels last.
What I would actually do
Do not lose sleep over direction and angle. If you have a south-ish roof at a normal pitch, fit the panels as the roof lies and you are within a few per cent of the best you could ever do. If your roof faces east and west, use both slopes rather than cramming everything onto the smaller south-facing bit, and enjoy the fact that the wider spread often suits real household use better anyway. Only rule out a face if it points broadly north. Spend your energy instead on the things that move the money: keeping the panels out of shade, sizing the system to what you actually use, and shifting heavy appliances into daylight. A roof that looks second best on paper frequently saves the most in practice. If you are still weighing up the whole idea, is solar worth it runs through the payback, and the basics cover how a system fits together.
Common questions
Which direction should solar panels face in the UK?
Due south gives the most electricity over a year. South-east and south-west lose only a few per cent, and due east or due west drop output by roughly 15 to 20 per cent, which is often a fair trade for generation spread across more of the day. North-facing is best avoided where you have a choice.
What is the best angle for solar panels in the UK?
About 35 to 40 degrees from horizontal gives the highest annual output, which is close to a typical British roof pitch. Anything from roughly 20 to 50 degrees is within a few per cent of ideal, so most standard roofs are fine as they are without a special mounting frame.
Are east-west facing solar panels worth it?
Often yes. An east-west split makes a bit less total power than a south array but spreads it across morning and late afternoon, which lines up better with when many households are home. Since self-used power is worth more than exported power, this can save more money in practice despite the lower total.
Do solar panels work if my roof does not face south?
Yes. East and west roofs still generate around 80 to 85 per cent of a south roof's output, and south-east or south-west lose only a few per cent. Only a north-facing roof produces so much less that it is usually not worth prioritising. Shade tends to matter more than the exact direction.
How much does shade reduce solar output?
More than its area suggests, because panels wired in a string can drag each other down. A single shaded panel can cut the whole string below what the sunlit panels would give alone. Power optimisers or microinverters limit the damage by letting each panel work independently, which is worth it where shading is unavoidable.