Solar roof tiles against conventional panels

Solar tiles put the generating surface into the roof covering itself rather than on brackets above it. They look considerably better, cost considerably more, and generate somewhat less per square metre.

Whether that trade is worth making depends almost entirely on whether the roof is being replaced anyway, and the decision gets much easier once the premium is expressed as a number rather than a feeling.

What they are

Conventional panels are mounted on rails above the existing covering. Solar tiles, sometimes called integrated or in-roof systems, replace a section of the covering, sitting flush in the roof plane with a weatherproofing tray beneath.

The category covers two quite different things:

Integrated panel systems, where conventional-sized panels sit in a flush tray. Mature, widely installed, and much closer to standard panels in cost.

Individual solar tiles, sized like a slate or tile. The most convincing visually and by far the most expensive per kilowatt.

Most people asking about solar tiles are best served by the first, and most headline horror stories about cost come from the second. Establish which one a quote describes before reacting to its total.

The case for them

Appearance. They sit flush and read as part of the roof. On a prominent elevation, or a property where the look genuinely matters, this is a real benefit rather than vanity.

Planning. The English permitted development conditions require roof equipment to project no more than 200mm from the roof slope, which conventional rails satisfy anyway, but in conservation areas, where the restrictions bite hardest on prominent elevations, a flush system is sometimes acceptable to a planning officer where a raised array is not. It does not remove the need to check, and for a listed building it changes nothing about needing consent.

New roofs. If the covering is being replaced anyway, you are not paying for tiles you then discard, and the in-roof trays actually displace some covering cost. The incremental cost against a new roof plus conventional panels narrows sharply.

VAT. Both routes qualify for the zero rate on energy saving materials until March 2027, so the comparison is clean of tax distortion.

The case against

Cost. Materially higher per kilowatt than a conventional array, whose 2025/26 medians sit at £1,697 to £1,780 per kilowatt in the government’s data. Integrated systems price above that band; individual tile systems can price at multiples of it.

Running temperature. Panels lose efficiency as they warm. A flush system has less air circulating behind it than one mounted on rails, so it runs hotter and produces slightly less for the same rated capacity. Modest, and real, and it belongs in the generation estimate rather than the footnotes.

Repair access. A conventional panel can be unbolted. An integrated one is part of the weatherproofing, so replacing a failed unit is more involved and more expensive.

Fewer installers. A smaller pool of people who have done many of them, and the flashing detail is where these systems leak if done poorly.

Price the appearance, explicitly

An illustration of the honest comparison. A conventional 4kW array at the median costs about £7,100 and returns around £650 a year in the standard worked example. Suppose the integrated quote for the same roof lands at £8,600, a £1,500 premium for the same capacity generating slightly less.

That premium is roughly two and a half years of the system’s annual saving, spent on how the roof looks. For a gable end nobody sees, that is a poor trade. For the front elevation of a period property you intend to live in for decades, it may be the best £1,500 in the whole project. The point is not the verdict; it is that the question “what is the appearance worth to me, in pounds” now has a number to be compared against.

When it is clearly the right choice

Two situations:

The roof is being replaced. Then the comparison is new covering plus panels against integrated units, and the gap is much smaller than it appears from retail prices.

A new build. Same logic, decided at design stage, where the integrated system is priced into the roof rather than onto it.

When it is clearly not

If you have a sound roof with years of life left, and no planning or aesthetic constraint, a conventional array on a good roof is more capacity for less money, easier to service and generating slightly more.

The honest framing: you are buying appearance. That is a legitimate thing to buy, and worth being clear that it is what you are buying.

Questions for a quote

• Is this an integrated panel system or individual tiles?
• What capacity fits, against a conventional array on the same roof?
• What generation estimate, and does it account for the higher running temperature?
• What is the flashing detail, and what is the guarantee against water ingress?
• How is a failed unit replaced, and what does that cost?
• How many of these has this installer fitted?

That last question matters more here than for conventional panels. The weatherproofing is doing a job the roof covering used to do, and it is not forgiving of inexperience.

Compare on the same basis

Get both quotes: integrated and conventional, on the same roof. Compare cost per kilowatt peak and the two generation estimates side by side, then run both through the projection with your own consumption and rates.

Then decide what the appearance is worth to you, as a number, and see whether the difference is smaller or larger than that. It is the rare question in home energy where the honest answer can legitimately be “the pretty one”, provided the price of pretty was read before it was paid.