Roof Orientation, Pitch and Shading for Solar Panels

The best roof direction for solar panels in the UK is south. Panels facing south capture the most sunlight because the sun sits in the southern half of the sky all day, and every UK guidance source agrees on this point¹. But south is the ideal, not the entry requirement. Panels perform well facing anywhere between south-east and south-west, at an angle of 20 to 50 degrees, which covers the great majority of British houses³. An unshaded east or west roof still generates well, at around 15% less than south, and a north-facing roof produces around 30% less, which is why most consumer guidance does not recommend it⁴.

Two things matter more than the perfect compass point. The first is pitch: a slope of 30 to 40 degrees is ideal, and most UK roofs already fall close to that⁵. The second is shade, and it outweighs angle. A modest roof facing the wrong way but in full sun will usually beat a perfectly oriented roof under a tree, because shading hits the whole array at once. This page explains what each roof direction delivers, how steep is steep enough, how much shade is too much, and what an installer will actually check before quoting.

Which way your roof faces, and how much it really costs you

South is the benchmark. Panels facing south generate the most electricity because they capture as much sunlight as possible through the middle of the day¹, and consumer guidance is blunt that you will need a mainly south-facing roof for the best power output, with south-west or south-east also good². The Energy Saving Trust puts it more loosely: ideally a roof that faces south, "more or less", and is not shaded⁷. That "more or less" is the practical point, because the sun does not sit due south all day. It travels from east to west through the southern sky, so any roof that looks at that arc for most of the day collects nearly the full benefit.

The tolerance band is wide. The Centre for Alternative Technology states that solar panels perform well facing anywhere between south-east and south-west, at an angle of 20 to 50 degrees³. Scottish Government planning guidance says the same in planning terms: ideally panels face between south-east and south-west to maximise the amount of light⁸. The Renewable Energy Consumer Code, which governs how member installers must behave, notes that a south-west or west-facing roof would also be suitable, though a little less productive⁹. So a roof that a compass would call south-south-west is not a compromise, it is simply a good roof.

What this means for a household is that orientation rarely rules a home out on its own. The roof surfaces most British houses have, facing the front and back of the property, will usually include something between east and west through south. The genuine deal-breakers are a roof that faces north on a steep pitch, or a roof that is heavily shaded, and those are covered below. If in doubt, an installer's survey will model the actual generation figure for your specific roof rather than relying on rules of thumb⁴.

Roof pitch: the 30 to 40 degree zone

Pitch is the second half of the geometry. The sun's height in the sky changes through the year, highest in summer and lowest in winter, and the panel angle determines how squarely the light strikes the glass. UK guidance converges on a narrow answer: a roof sloped at an angle of around 30 to 40 degrees is ideal for solar panels⁵. The Chartered Institute of Plumbing and Heating Engineering says the same, adding that the roof should ideally face south, in an unshaded location, at a pitch angle of 30 to 40 degrees¹⁰. Which? puts it plainly: a 30 to 40 degree slope is ideal⁴.

Not every source lands on exactly the same number within that zone. One installer guide puts the optimum pitch on a south-facing roof at around 40 degrees, to maximise energy generation and ensure consistency throughout the year¹¹. Which?'s analysis of maximum output describes the ideal UK roof as a large, south-facing, 30 to 40 degree pitched roof in the south of England, free from shading¹². Snowdonia National Park's energy efficiency advice for householders also cites a pitch of 30 to 40 degrees¹³, and a news analysis of a combined solar and heat pump offer repeats that 30 to 40 degrees is ideal, with around 30 degrees best in one reading¹⁴.

The wider tolerance matters more than the exact optimum. A certification body states that if your roof is angled between 25 and 45 degrees, then this will be fine to house your panels¹⁵. Combined with the Centre for Alternative Technology's 20 to 50 degree range³, the practical message is that almost every conventional British pitched roof qualifies. Roofs shallower than about 20 degrees lose some winter performance because the panels lie flatter than the low winter sun, and very steep roofs lose some summer performance, but neither extreme is common on UK housing. For solar thermal, the equivalent guidance is about 30 to 50 degrees¹⁶.

The drawbacks of roofs facing north

A north-facing roof looks away from the sun's entire path across the southern sky, and the numbers reflect that. Which? states that a north-facing roof produces around 30% less energy than a south-facing one⁴. The Energy Saving Trust goes further and says it does not recommend installing panels on a north-facing roof, because east or west-facing roofs still work but a north roof does not give a worthwhile return¹⁷. Its installation guidance is equally direct: "We don't recommend installing panels on roofs that face north, you won't get enough sunlight to make it worth your while."¹

There is one dissenting voice worth recording. Smart Energy GB notes that while south-facing roofs typically perform best, you can still benefit from solar energy with north-facing roofs¹⁸. That is true in the narrow sense that any panel pointed at the sky generates something, particularly from diffuse light on cloudy days. But a 30% output loss on the system's total lifetime generation changes the payback calculation substantially, and no other guidance in the UK consumer canon takes the north-facing case.

One exception exists, and it is counterintuitive. Shallow-pitched north-facing roofs can also be used, typically if the pitch is less than 10 degrees¹¹. The logic is that a nearly flat panel does not really "face" anywhere: it points mostly upwards, so the compass direction matters far less than it does on a steep roof. On a normal pitched roof of 30 to 40 degrees, however, the north-facing surface is genuinely turned away from the sun, and the loss is real and permanent. A household with only a north-facing pitched roof is usually better served by looking at other options, such as a ground-mounted array, than by accepting a permanently underperforming roof.

East and west roofs: a different daily shape, not a lesser one

East and west-facing roofs are genuinely viable, and the guidance is more positive about them than many householders expect. An installer guide states that east and west facing roofs still present a good opportunity for solar installations and offer good potential for energy generation¹¹. MCS and the Energy Saving Trust jointly make the point in eligibility terms: if you have an unshaded roof that faces east, south or west, there is a good chance that your home is suitable for solar¹⁹. The Renewable Energy Consumer Code adds that a south-west or west-facing roof would also be suitable, though a little less productive⁹.

The output penalty is modest. Which? puts an east or west-facing roof at 15% less energy than south⁴. What that headline number hides is that the loss is not spread evenly across the day, it is a shift in timing. South-facing panels peak around the middle of the day, while west-facing panels do better in the afternoon and early evening¹. East-facing panels mirror that, producing more in the morning. For a household that is out at work all day and uses its electricity in the morning and evening, that shifted profile can be a better match for consumption than a south-facing array's midday peak, because more of the generation is used rather than exported.

That is the real question to ask about an east or west roof: not "how much will I generate?" but "when will I generate?". A west-facing array producing into the early evening feeds the cooking and lighting load directly. An east-facing array covers the morning kettle and shower. Neither matches a south roof for total kilowatt-hours, but total generation is only half of the value equation; the other half is how much of it the household uses on site, which is what actually reduces bills and dependence on a supplier. Our page on east and west-facing solar panels covers this trade-off in detail.

Why shade matters more than the ideal tilt angle

If there is one factor that outranks orientation, it is shade. The Energy Saving Trust's summary is that an unshaded, south-facing roof is ideal for maximum performance¹⁷, and the Renewable Energy Consumer Code describes a large, unshaded, predominantly south-facing roof space as the fortunate ideal for solar panels⁹. Note the order of those descriptions: in each, "unshaded" comes first. Shade is not a gentle reduction. When a shadow falls across part of a conventional string array, the affected panels drag down the output of the whole string, so a small area of shade can cost a disproportionate amount of generation.

The threshold that consumer guidance gives is a roof with 20% shading or less is best⁴. Beyond that, official guidance turns firm: Bromley Council tells householders that if your roof is heavily shaded, solar panels may not be the most suitable option²⁰. The same standard applies to solar water heating, where a south facing roof which is free of shading is described as ideal²¹. Sources of shade include trees, chimneys, dormers, satellite dishes and neighbouring buildings, and they matter most in winter when the sun is low and shadows are long. A chimney that casts no shadow in June can blanket half a roof in December.

This is why the survey matters as much as the roof itself. Shade is specific to your house and its surroundings in a way that compass direction is not, and it changes with the seasons. Some shade is fixable: trees can be trimmed, and the layout of panels across the roof can be arranged so that the shaded zone is minimised or isolated¹. Some shade is not fixable, and the honest answer in those cases may be that the roof, however well it faces, is not the right one for solar. For more on the mechanics, see how shade affects solar panel output.

Dealing with shade you cannot remove using module-level power electronics

Not every shaded roof is a lost cause, and the industry has hardware that addresses the problem directly. If shading is unavoidable, an installer might recommend microinverters or power optimisers. These let each panel work independently, so a shadow on one panel reduces that panel's output rather than pulling down the whole array¹. Trimming trees that cause partial shade is listed alongside these options as a first response¹.

It is important to be clear about what this hardware does and does not do. As one installer guide states, the use of optimisers will reduce the losses of the overall system, but individual panel losses will still affect performance¹¹. In other words, module-level electronics recover much of what a shaded string would otherwise lose, but they cannot make a shaded panel generate as if it were in full sun. The shaded panel still produces less; the difference is that its neighbours no longer share the penalty.

For a household weighing this up, the decision points are these:

• Partial, predictable shade (a chimney or one tree, affecting a corner of the roof for part of the day) is the classic case for optimisers or microinverters, and the economics often still work.
• Heavy, all-day shade across most of the roof is not solved by any hardware, and official guidance is that solar may not be the most suitable option in that situation²⁰.
• Fixable shade, such as an overgrown tree, is worth dealing with before the survey, because it changes both the quote and the system design.

The choice between the two technologies has its own trade-offs, covered on our pages for power optimisers, microinverters and microinverters vs string inverters.

Tilt frames, panel spacing and the 0.6 metre rule on flat roofs

Flat roofs are a different engineering problem, and the first thing to say is that they are a solved one. Solar panels can be installed on both pitched and flat roofs; on a flat roof, the panels need to be tilted and spaced to avoid shading, meaning one row shading the row behind it⁶. Which? confirms the same point against the popular belief otherwise: solar panels can be installed on flat roofs too². The Energy Saving Trust adds that panels on flat roofs are normally tilted up to help maximise energy production¹⁷.

The tilt and the spacing are linked. Because the panels are raised on frames rather than lying on the roof, each row casts a shadow behind it, so rows must be set far enough apart that the shadow of one does not fall on the next, especially in winter when the sun is low. This spacing requirement means a flat roof needs more area for the same number of panels than a pitched roof does. There are also structural questions: a flat roof installation might need additional mounting systems, and the roof must support the extra weight, so it might cost more than a pitched roof installation¹. On the plus side, a flat roof offers more flexibility over the angle of the panels, since the frames, not the roof, set the tilt¹.

Planning rules add a specific limit. On a flat roof, panels should project no more than 0.6 metres from the plane of the roof²². For comparison, on a pitched roof the 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 slope²³. These are the permitted development limits that apply to most houses, and they matter for flat roofs in particular because a taller frame for a steeper tilt can breach the projection limit. Our page on flat roof solar permitted development rules covers the full conditions.

Roof needs for solar thermal compared with heat pumps

Solar water heating collectors look at the same sun but ask a slightly different question of the roof, because they capture heat rather than light and are less forgiving of direction. Solar hot water collectors work best on a south-facing roof, or somewhere between east to west, but not north facing²⁴. OFTEC's off-grid guidance says panels are usually sited on a south-facing roof and use the sun's heat to warm water²⁵. A Scottish Government feasibility study assigned suitability to homes with roofs facing South, South-West or South-East²⁶.

The pitch guidance for thermal is similar to PV but with its own numbers. Northern Ireland's official guidance states that all solar panels should be mounted on south facing roofs, between south-east and south-west, at an angle of about 30 to 50 degrees¹⁶. Which?'s renewable heating guide adds that solar thermal panels work best on south-facing roofs that are not shaded by trees or other buildings²⁷. Welsh Government guidance rounds it out: for best performance solar collectors need to face between south-east and south-west and be free of the shade of trees and buildings²⁸.

Two related products sit at the edges of this picture. Solar roof tiles, which replace rather than sit on the roof covering, follow the same physics: south facing works best²⁹, and the Energy Saving Trust notes they are best suited to existing roofs³⁰. Heat pumps, meanwhile, have no roof orientation requirement at all, since an air source unit sits at ground level and takes heat from the air rather than the sun; a household combining a heat pump with solar PV gets the roof question only on the PV side. The roof requirements for solar water heating, including how much roof space it needs, are covered on our solar water heating page.

The checks an installer makes before giving a quote

A quotation should never be built on the roof's compass direction alone, and a good survey is a technical exercise, not a sales visit. Which? sets the standard: a good surveyor should do a technical site survey including looking at roof orientation, measuring roof tilt, assessing roof quality inside and out, recording any risks of shade on the panels, looking at your consumer unit and metering, asking about your electricity use, and discussing where to locate cables and equipment⁴. Every one of those items feeds the generation estimate and the system design.

Structural checks are a formal requirement, not a courtesy. East Hertfordshire District Council's guidance states that you will need to check that the roof can support the additional wind, snow and static load imposed by the solar panels, and that it complies with Part A: Structure³¹. The Welsh Government's building regulations guidance says the same in plainer terms: the adequacy of the existing roof to carry the load, the weight, from the panels will need to be checked and proven³². This is why a surveyor may ask about the age of the roof, look in the loft at the rafters, and in some cases ask for a structural calculation.

What the survey covers, in the order a household will experience it:

1. Roof orientation and pitch, measured rather than guessed, since these set the baseline generation figure⁴.
2. Overshading, from trees and other buildings, recorded as a percentage that feeds directly into the performance estimate³³.
3. Roof condition and structure, inside and out, including whether the roof can carry the additional wind, snow and static load⁴.
4. Your electricity use, because the system size is matched to consumption, not just to roof area⁴.
5. Cabling, consumer unit and equipment locations, agreed before installation day⁴.

Some schemes formalise this stage. Under the Solar Together group-buying scheme, once you accept your offer a surveyor will visit your property to assess whether your roof is suitable for a solar installation and confirm the number of panels, their location, and other details such as cabling locations and colour³⁴. If a quote arrives without anyone having assessed orientation, pitch and shading, that is a gap in the process, not a streamlined one. The full sequence from survey to handover is on our solar panel installation page.

How a suitable roof affects your energy self-reliance

Roof geometry decides how much of your own electricity you can make, and that is the whole point of the exercise. A household with an unshaded south, east or west roof and a pitch anywhere in the 25 to 45 degree band can generate a meaningful share of what it consumes, cutting both its bills and its reliance on a supplier¹⁹. The better the roof, the more of the household's demand the array covers directly, and the less the home depends on imported power and the price a supplier chooses to charge for it.

The honest limits are worth stating alongside the benefits. A north-facing pitched roof, or a heavily shaded one, produces so little that the system may never pay its way, and the guidance in those cases is not to proceed¹. Even a perfect roof does not deliver independence on its own: the panels generate nothing after dark, output falls in winter, and the home remains connected to the grid for the balance of its needs. What a good roof buys is a permanent, on-site source of power that no supplier controls and no tariff can claw back, with the roof's direction and shade determining how large that source is.

That is why the survey numbers deserve attention rather than a glance. The difference between a heavily shaded roof and a clear one, or between south and north, is the difference between an array that carries the household through most of the year and one that underdelivers for twenty-five years. The roof you have is fixed; the design choices, panel layout, module-level electronics and how the generation is used, are not. For the wider picture of how solar fits a household's energy independence, see solar panels and household energy independence, and for the overall system, our solar PV guide.