In short
- South-facing, unshaded roofs generate most. The Energy Saving Trust says east or west roofs get around 15 to 20% less, and it doesn't recommend north-facing roofs.
- Shading from trees, chimneys and neighbouring buildings can matter as much as orientation, and optimisers or microinverters can limit its effect.
- Roof-mounted panels on houses are usually permitted development. The rules were updated on 27 August 2026, with a transitional period to 27 August 2027.
- Building Regulations normally apply, covering the roof's ability to carry the load and the electrical work.
- Systems up to 3.68 kW on a single-phase supply are notified to UK Power Networks after connection under G98. Larger systems need approval in advance under G99.
Which way your roof faces
An unshaded, south-facing roof gives the most generation over a year. The Energy Saving Trust says systems facing east or west tend to get around 15 to 20% less energy than one facing directly south, and it doesn't recommend panels on north-facing roofs.
East and west roofs still work well for many homes. The Energy Saving Trust points out that east-facing panels generate more in the morning and west-facing panels more in the afternoon and early evening, which can match when a household actually uses electricity. Some homes split panels across both slopes to spread generation through the day.
- South, south-east and south-west: usually the strongest annual output.
- East or west: lower annual output, but often a good match for morning or evening use.
- Split east and west: needs an inverter that can handle two separate strings or panel-level electronics.
- North: rarely worth it on a pitched roof. A flat roof or garden array may be a better option.
Roof pitch, size and how many panels fit
The MCS method for estimating generation uses tables for each postcode zone that give the expected output per kWp for each combination of roof pitch and orientation. So the angle matters as well as the direction. Most pitched roofs in Kent fall in a range that works well, and a very shallow or very steep roof simply produces a little less.
Space is often the bigger limit. The Energy Saving Trust gives a rough guide to how many panels typically fit:
| House type | Typical number of panels |
|---|---|
| Mid-terrace house | About 4 |
| End-terrace or semi-detached house | About 8 |
| Small detached house | About 12 |
| Large detached house | About 16 |
Chimneys, rooflights, dormers, vent pipes and hips all take space, and installers usually leave clear margins at the edges of the roof. The Energy Saving Trust also notes that grid capacity and export limits can influence the final system size. Rain helps keep panels clean if they are tilted at 15 degrees or more, according to the Energy Saving Trust.
Shading from trees, chimneys and neighbours
The Energy Saving Trust says shading can have an even bigger impact than orientation, and a shaded south-facing roof can produce less than a sunny east or west one. Common causes are trees, chimneys, dormers and neighbouring buildings, and the shadow pattern changes through the day and across the seasons.
- On a standard string system, a shaded panel can hold back the others on the same string.
- Optimisers or microinverters let each panel work independently, so one shaded panel doesn't drag down the rest. The Energy Saving Trust notes that on an unshaded roof they won't increase generation, although they add panel-level monitoring.
- Trimming trees, where you are allowed to, can make a real difference. Trees protected by a tree preservation order need the council's consent first, and trees in a conservation area normally need notice to the council.
- Under the MCS method, the installer applies a shade factor to the estimate. A factor below 1 means shading is expected to reduce output, and the quote must say so.
Roof condition, coverings and structure
Panels are expected to last 25 years or more, according to the Energy Saving Trust, so the roof underneath needs to last too. A good survey looks at the covering, the battens and the timbers, not just the view from the drive.
- Roof condition: slipped or cracked tiles, worn mortar on ridges and moss should be sorted first. If the roof will need replacing in the next few years, it is usually sensible to do that before fitting panels, because removing and refitting them adds cost.
- Concrete interlocking tiles: usually the most straightforward covering to fix to, using hooks that sit under the tiles.
- Plain clay tiles and natural slate: common on older Kent houses. They can be fitted to, but need care and the right fixings to avoid cracking and leaks, which can add time and cost.
- Structure: the roof must carry the extra weight and the wind loads. The Planning Portal says the existing roof's ability to carry the load will need to be checked and proven, and some strengthening may be needed.
- Roof warranties: MCS's Customer Commitment says installers should tell you if the work might invalidate an existing warranty, such as a roof warranty.
Flat roofs, garages and ground-mounted panels
The Energy Saving Trust says panels on flat roofs are normally tilted up on frames, and many systems are weighted down with ballast rather than fixed through the roof covering, so the roof stays watertight. A ballasted system needs a roof strong enough for the extra weight. Where it isn't, fixings must be properly sealed. Sometimes it makes sense to renew the roof covering first.
- Under the permitted development rules, the highest part of panels on a flat roof can't be more than 600 mm above the highest part of the roof, excluding the chimney.
- On a flat roof on designated land, which includes conservation areas, National Landscapes and World Heritage Sites, you must apply to the council for prior approval.
- Garages and sheds can take panels if the roof is strong enough. The Energy Saving Trust notes you should factor in the cost of an electricity supply if the building doesn't have one.
- Ground-mounted arrays in the garden have their own permitted development rules and are easier to clean, but need protecting from damage and shading.
Permitted development for roof panels after 27 August 2026
In England, solar panels on a house are usually permitted development, which means no planning application is needed if the limits and conditions are met. The Planning Portal says the permitted development right for solar on a house, a block of flats or a building within its grounds was updated on 27 August 2026. There is a 12-month transitional period to 27 August 2027, during which you can follow either the rules as they were immediately before 27 August 2026 or the new rules.
Under the new rules for a house, the Planning Portal lists these limits:
- On a pitched roof, panels must not be installed above the highest part of the roof, excluding the chimney, and must project no more than 200 mm from the roof slope.
- On a flat roof, the highest part of the equipment must be no more than 600 mm above the highest part of the roof, excluding the chimney.
- On a wall, balcony or roof enclosure that abuts a highway, panels must not protrude more than 0.2 metres. On any other wall, balcony or roof enclosure, the limit is 0.4 metres.
- Panels must not be installed on a building within the grounds of a listed building, or on a site designated as a scheduled monument.
- In a conservation area or World Heritage Site, panels must not be fitted to a wall, balcony or roof enclosure that fronts a highway.
- Plug-in solar must not be installed on a wooden wall, balcony or enclosure, or on any exterior clad in timber.
Conditions also apply. Equipment should be sited, so far as practicable, to minimise its effect on the appearance of the building and the amenity of the area, and removed as soon as reasonably practicable when it is no longer needed.
Listed buildings, conservation areas and flats
- Listed buildings: permitted development doesn't cover panels on a building within the grounds of a listed building, and fixing panels to a listed building itself is likely to need listed building consent. Speak to the council's conservation officer before you get quotes.
- Conservation areas: roof panels can still be permitted development, but not on a wall, balcony or roof enclosure that fronts a highway, and flat roofs need prior approval. Kent has many conservation areas, so check your council's maps.
- Flats: the Planning Portal gives separate limits for a block of flats, including the 200 mm projection limit and the same rules on listed buildings and conservation areas.
- Leaseholders: the Planning Portal notes that you may need permission from your landlord, freeholder or management company, separately from planning.
Planning in Kent is handled by the district and borough councils, plus Medway Council. If you are unsure, check your address on your council's planning pages or ask for pre-application advice.
Building Regulations for solar panels
The Planning Portal says Building Regulations will normally apply when you install solar panels on a roof. The two main areas are the structure, because the roof must be able to carry the load, and the electrical installation.
Most installers are registered with a competent person scheme, which lets them self-certify that the work meets Building Regulations without a separate application to Building Control. MCS's Customer Commitment says installers should explain what must be notified under Building Regulations and who is responsible, and give you any Building Regulations compliance certificate within 30 calendar days of completion. Keep it with your MCS certificate, as a buyer's solicitor will ask for both.
Telling UK Power Networks: G98 and G99
UK Power Networks is the distribution network operator for Kent. Every solar or battery system that connects to the grid must be notified to it or approved by it. The Energy Saving Trust says your installer will usually register the system for you.
| Route | When it applies | What happens |
|---|---|---|
| G98 connect and notify | A single installation up to 16 amps per phase, which is 3.68 kW on single-phase or 11.04 kW on three-phase | The installer connects the system and sends evidence of compliance to the network operator within 28 days of commissioning |
| G98 apply in advance | Several installations within those limits, for example across multiple homes | An application is made before connection |
| G99 | Installations above those limits, including where solar and battery inverters together exceed them | An application must be made and accepted before connection. Export limitation under G100 can sometimes keep a system within an agreed limit |
The figures come from the Energy Networks Association and the Welsh Government's technical note on the Engineering Recommendations. The Energy Networks Association notes that the total includes electricity storage, so solar and a battery together can move a system into G99. In practice, the homeowner is responsible, but the installer usually deals with UK Power Networks. Ask each installer which route applies to your quote and how long it may add.
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Sources
- Planning Portal: Solar equipment mounted on a house or a block of flats, rules before and after 27 August 2026: www.planningportal.co.uk/permission/common-projects/solar-panels/planning-permission-solar-equipment-mounted-on-a-house-or-a-block-of-flats-or-on-a-building
- Planning Portal: Solar panels, Building Regulations: www.planningportal.co.uk/permission/common-projects/solar-panels/building-regulations
- Energy Saving Trust: Solar panels, costs, savings and benefits (updated October 2026): energysavingtrust.org.uk/advice/solar-panels/
- Energy Saving Trust: Rooftop solar panel installation, step-by-step guide (October 2026): energysavingtrust.org.uk/solar-panel-installation/
- MCS: MIS 3002 Solar PV Systems standard, issue 6.0 (March 2026): mcscertified.com/wp-content/uploads/2026/03/MIS-3002_Solar-PV-Systems-V6.0-Final.pdf
- MCS: Customer Commitment, issue 1.1 (September 2026): mcscertified.com/wp-content/uploads/2026/09/MCS-Customer-Commitment_V1.1_2026.pdf
- GOV.UK: Building regulations competent person schemes: www.gov.uk/building-regulations-competent-person-schemes
- Energy Networks Association: Connecting generation to the electricity networks (G98, G99 and G100): www.energynetworks.org/industry/connecting-to-the-networks/connecting-generation-to-the-electricity-networks
- Welsh Government: Connecting on-site generation to the grid, technical note: www.gov.wales/connecting-site-generation-grid-technical-note-html