SOLARWATT Panels

What a glass-glass panel actually is

Most panels are glass on the front and a polymer back sheet on the rear. The back sheet is the cheap part and the weak part: it is a plastic laminate that slowly yellows, embrittles and, eventually, lets moisture reach the cells.

A glass-glass panel replaces that back sheet with a second pane of glass. The silicon is sealed between two sheets of an inert, UV-stable material that does not care about thirty British winters. The cells sit on the neutral axis of the sandwich, so flexing under wind and snow load puts far less stress on the cell interconnects.

SolarWatt build theirs in a medium form factor rather than the very large modules that have become common. Smaller modules are heavier per square metre but easier to handle safely on a domestic roof, less prone to twisting during install, and they let us fit the roof shape more tightly.

The warranty, and what it actually covers

There are two warranties on a solar panel, and they are easy to mix up, so we explain both plainly and fit panels where the two numbers match.

The performance warranty guarantees the panel still produces a stated percentage of its rated output after a given number of years. SolarWatt run theirs to 25 years. If the panel underperforms the curve, the claim is on output, not on whether the panel is physically intact.

The materials warranty, sometimes called the product warranty, covers the panel itself: defects, delamination, failure of the laminate. This is the one most manufacturers keep short, typically 10 or 12 years, because the back sheet is where the risk sits. SolarWatt run theirs to 25 years as well, which is only economically sensible if you believe the glass-glass construction will not fail.

A warranty is a manufacturer's own estimate of its failure rate, expressed in years. Read the length as a statement of confidence, not as a promise you will ever need to use.

How they are made, and the carbon arithmetic

Making a solar panel takes energy, mostly in refining polysilicon. That energy is the panel's embodied carbon, and it is paid up front, before the panel has generated anything.

Two things reduce the carbon per kilowatt hour generated. The first is making the panel with clean electricity in the first place: SolarWatt manufacture using renewable energy, so the up-front debt is smaller. The second, and the larger lever by far, is life. A panel that runs for 30 years spreads its embodied carbon over roughly twice as many kilowatt hours as one replaced at 15.

That is why we treat longevity as an environmental argument as much as a financial one. The greenest panel is not the one with the lowest factory footprint on a spreadsheet, it is the one still working in 2055.

What it looks like on a roof

Full-black framing, low sheen, and a uniform cell layout. From the ground the array reads as a single dark rectangle rather than a grid of blue squares.

We lay the array out to maximise the number of panels we can fit, then check the layout against shading, access for maintenance, and the fire-service setback rules where they apply. If we can add one more panel without compromising any of those, we add it: the marginal panel is the cheapest energy on the roof, because the scaffold, the labour and the inverter are already paid for.

If something goes wrong

You call us, not the manufacturer. We hold the install records, the string layout and the monitoring data, so in most cases we can tell which panel is misbehaving before anyone climbs a ladder.

Because the system monitors at panel level, a failing module shows up as one line diverging from its neighbours rather than as a vague drop in the monthly total. We raise the warranty claim, handle the replacement, and match the replacement panel to the string.

The honest downsides

Glass-glass panels are heavier than glass-backsheet panels. On an old or marginal roof structure that can matter, and we check it at survey.

They cost more per watt than commodity modules. If your only metric is pounds per kilowatt-peak on day one, they lose. Over 25 years, they do not.

Medium form factor means more modules, more mounting points, and slightly more labour than the very large panels some installers prefer.