Solar panels projects

The roof decides more than the panel does

Panel choice matters far less than most people expect. Modern all black monocrystalline modules from any reputable manufacturer sit within a few per cent of each other, and the difference that actually shows up on a bill comes from orientation, pitch, shading and how much of the roof can be used. A south facing roof at around thirty five degrees is the textbook case, but east to west splits are common here and often work better than they look on paper, because they spread generation across the morning and the evening rather than piling it into the middle of the day when nobody is home.

Lincolnshire throws up two roof types more than most. The shallow pitched interwar bungalow flattens the summer peak and softens the winter one, and it changes how far in from the edges the panels have to sit before wind uplift becomes the governing factor. Flat commercial and domestic roofs need ballasted or mechanically fixed mounting with the wind loading calculated rather than assumed, which is the part of a flat roof job that takes the time.

Mounting, and why it is worth arguing about

On a pitched roof the choice is between on roof rails and an in roof system that replaces the tiles under the array. In roof looks considerably better and is usually specified on new builds, where it goes on before the roof is finished. Retrofitting it to an existing roof means stripping tiles, so on an occupied house on roof rails are normally the sensible answer.

Large commercial roofs are a different discipline again. A trapezoidal metal roof takes a mini rail system fixed to the sheet profile, which spreads the load and avoids penetrating the weatherproofing more than necessary. That is what sits under our largest array, 758 panels on a distribution centre roof, and at that scale the mounting design and the roof survey take longer than the panels do to install.

Getting it connected

Every grid connected array has to be registered with the distribution network operator, and the threshold that matters is 16 amps per phase, which is 3.68kW on a single phase supply and about 11kW on three phase. At or below it the installation falls under Engineering Recommendation G98, which is connect and notify within 28 days. Above it, it becomes G99, which means applying and receiving approval before anything is energised.

That distinction is why a survey should establish the supply arrangement early. A G99 application takes time, and on a larger system the network operator may impose an export limit, which is normally workable but changes the design. It is far better to know at the quotation stage than after the scaffold is up.

What eastern England actually gives you

Lincolnshire is a good place to put solar on a roof. Eastern England is among the drier and sunnier parts of the country, the land is flat so there is very little shading from terrain, and clear coastal air helps once the sun is up. Generation is strongly seasonal, with the summer months producing several times what December and January manage, so a system should be sized around the year rather than around its best week.

Panels work from daylight rather than heat, which is why they keep producing on a cold bright day and why output holds up better through a Lincolnshire winter than people expect. Cool air actually helps, because module efficiency falls as the cells get hot. A still, baking July afternoon is not the best generating condition it looks like.

Self consumption is where the money is

A unit you generate and use yourself saves you the full retail price of buying it. A unit you export earns whatever your export tariff pays, which is normally a good deal less. So the single biggest lever on what a system is worth is not its size, it is the proportion of its output you actually consume rather than send back.

That is why timing matters. Running the washing machine, the dishwasher or the car charger through the middle of the day rather than the evening changes the economics without changing the hardware. It is also the argument for storage, which is covered on the battery storage page.

Getting paid for what you export

The Smart Export Guarantee is the mechanism that pays for exported units. Under the Ofgem scheme, every licensed electricity supplier with 150,000 or more domestic customers has to offer at least one export tariff, and the rate has to be greater than zero. Beyond that the suppliers set their own rates, which is why they vary so widely and why it is worth checking rather than defaulting to whoever supplies your import.

To claim it the installation has to be certified under the Microgeneration Certification Scheme or an equivalent. That certificate is issued at handover and it is the document your supplier will ask for, so it is worth keeping somewhere you can find it.