Solar Roof Tiles vs Panels Energy Output Calculator

How this calculator works

This calculator works in ranges rather than single figures, because real quotes, yields and tariffs genuinely vary that much. It starts from typical UK price, output and savings ranges drawn from published 2026 industry guides and official scheme documentation, then scales them by the quantities you enter and adjusts them for each choice you make below. The result is a low-to-high band that a realistic outcome is likely to fall within, not a promise of the figure you will achieve.

At the same installed kWp, solar tiles typically produce around 5 to 10 percent less than conventional panels over a year, roughly 760 to 880 kWh per kWp against 830 to 950, because tiles run hotter in the roof plane and their cell packaging is less efficient. The bigger practical gap is capacity itself: tiles are typically 10 to 20 percent efficient against 18 to 25 percent for panels, so the same roof area holds noticeably less tile capacity than panel capacity.

System size

Solar systems are sized in kilowatts peak (kWp), the output of the panels under standard test conditions. A 4 kWp system of around 10 modern panels is the most common choice for a UK three bedroom home, while larger households, or homes with an electric vehicle or heat pump, often go to 6 kWp or more. Bigger systems cost less per kWp because fixed costs such as scaffolding, the inverter and installer overheads are spread across more panels, and the calculator reflects that economy of scale.

Region (solar resource)

The same panels generate more in Cornwall than in Caithness. The industry baseline is around 850 kWh per year for every kWp installed on an unshaded south-facing roof in an average UK location, with southern England running around 5 percent above that and Scotland 10 to 15 percent below. The calculator scales its output and savings figures accordingly.

What else affects the figures

Tiles cost roughly two to three times as much per kWp as panels, so on pure energy economics panels win comprehensively; a tile system earns its premium where aesthetics or planning rules it in, on conservation properties, listed buildings and high-end new builds where conventional panels would be refused or unwanted. Tiles integrate best when the roof is being built or replaced anyway, offsetting some conventional roofing cost. Output-wise, both technologies respond identically to orientation, shading and region, so the percentage gap between them stays roughly constant whatever the roof; the choice is really cost and appearance, with output a secondary consideration.

Certification, planning and grid connection

If a calculation here prompts a project, the practical next step is an MCS-certified installer’s survey: MCS installers must provide a location-specific generation estimate using the standard industry methodology, which turns the broad ranges on this page into a figure for your actual roof. Most domestic solar work falls under permitted development, with the usual exceptions for listed buildings, flats and conservation areas, and installations must be notified to the district network operator under the G98 or G99 procedures, which a competent installer handles as part of the job.