Standard solar panels sit on top of your existing roof tiles, attached via brackets and rails. In-roof systems are different — the panels replace a section of roof tiles entirely, sitting flush with the surrounding tile line.
Both are perfectly viable in 2026. They cost different amounts, look different, and suit different properties. This is a practical guide to choosing between them.
On-roof solar panels (the default)
On-roof — sometimes called “rooftop” or “retrofit” solar — is what most UK homes have. The mounting hardware (rails, hooks, clamps) sits between the panels and the tiles. The panels sit roughly 50–80mm above the tile surface.
Pros:
- Cheaper — typically £6,500–£8,000 for a 4kW system
- Faster to install — usually a single day
- Easier to retrofit to existing roofs
- Easier to replace a single faulty panel
- Better airflow underneath — slightly higher generation in hot weather as the panels are cooled by air circulation
Cons:
- Visible mounting hardware — silvery rails are visible at the array edges
- Higher profile — panels stand proud of the tile line
- Slightly higher wind loading — the gap between panel and tile creates uplift force
- Pigeons can nest underneath — common in some Sussex towns, needs bird mesh if it’s an issue
In-roof solar panels (integrated)
In-roof panels replace a section of roof tiles. The most common system in the UK is GSE In-Roof, which uses a plastic tray system that holds the panels flush with the surrounding tiles. Other manufacturers (Easy Roof, Solrif) work similarly.
Pros:
- Cleaner aesthetics — panels look like they belong on the roof, almost flush with the tile surface
- Lower profile — no visible mounting hardware
- Lower wind loading — no uplift gap, lower forces in storms
- No bird issues — nothing to nest under
- Better for conservation areas and listed buildings — planning officers often prefer the lower-impact look
- Replace tiles + add solar in one job — if your roof needs work anyway, in-roof can be net cheaper than re-tiling then adding on-roof solar
Cons:
- More expensive — typically £800–£1,500 more than equivalent on-roof for a 4kW system
- Slightly slower to install — usually 1.5–2 days
- Harder to replace a faulty panel — needs more roof work to swap one out
- Slightly lower generation in hot weather — less airflow cooling underneath, ~1–2% less efficient in peak summer (negligible over the year)
- Roof structure check — your roof needs to be in good condition. In-roof shouldn’t be installed onto an older roof that needs replacing soon.
Cost comparison: 4kW system 2026
| Install | On-roof | In-roof |
|---|---|---|
| 4kW solar PV | £6,500–£8,000 | £7,500–£9,500 |
| Install time | 1 day | 1.5–2 days |
| Panel profile above tiles | ~70mm | ~10mm (flush) |
| Bird mesh needed? | Often yes (£200–£500) | No |
| Conservation area approval rate | Lower | Higher |
When to choose in-roof
In-roof typically makes sense when:
- You’re re-tiling the roof anyway — adding in-roof solar at the same time saves money overall (you skip the tiles that would have been replaced under the array)
- Your property is in a conservation area — planning officers approve in-roof more readily than on-roof on heritage streets
- You want the cleanest aesthetic — particularly visible from the street
- You live somewhere with persistent pigeon issues — coastal Sussex towns, some Brighton terraces
- You’re building a new home — in-roof integrates better into a new-build construction sequence than retrofit on-roof
- You’re in a South Downs National Park or AONB property — the lower visual impact eases planning
When to choose on-roof
On-roof typically wins when:
- You’re on a tighter budget — the £800–£1,500 saving is real
- Your roof is sound but not new — disturbing tiles for an in-roof job carries small risk; on-roof is gentler
- You want the install done in a day
- You’re not in a conservation area and aesthetics aren’t a priority
- You want the easiest path to panel replacement if one fails
Hybrid: in-roof on a rear slope, on-roof on a front slope
Some Sussex installs split the difference. We’ve done several where the front roof (street-facing, listed building) gets in-roof panels for a clean heritage look, while the rear roof gets standard on-roof panels for cost savings.
A mixed install needs two separate strings (one per roof slope) but most modern inverters handle this without issue.
Coastal considerations
On coastal properties — Bognor Regis, Worthing, Shoreham-by-Sea, Brighton seafront — in-roof has the additional benefit of lower wind loading. Storm winds and salt exposure both favour a flush integrated install. For seafront properties we often recommend in-roof even where the budget is tight.
New-build properties
For homes in Forge Wood and Kilnwood Vale (Crawley), Highwood and Kilnwood Vale (Horsham), Graylingwell (Chichester), and West Durrington (Worthing), in-roof integration is often the cleanest option — particularly if you’re commissioning the panels during construction or shortly after move-in. See our Solar Panels for New-Build Homes guide for more.
What about generation differences?
In-roof panels generate roughly 1–2% less energy over the year compared to identical on-roof panels because they run very slightly hotter (less air cooling underneath). For a 4kW system that’s about 35–80 kWh less per year — under £15 in lost savings. Negligible compared to the aesthetic and planning benefits in most cases.
Bottom line
There’s no universally “better” choice. On-roof is the right answer for the majority of Sussex homes — it’s cheaper, faster, and the aesthetic difference doesn’t matter for most properties. In-roof is the right answer when looks, planning, or coastal/new-build conditions tip the balance.
We design every install around the specific property. If you want to know which makes more sense for your home, a free site survey is the way.
