What actually happens when solar and battery go in

What is the installer actually checking at survey?

Five things, and only one of them is the roof.

The roof itself: orientation, pitch, shading through the day, the state of the tiles or slates, and whether the timbers will take the extra load. South facing is best but east and west split arrays often suit a household better, because they generate at breakfast and dinner rather than all at midday when nobody is in.

The loft, because that is where the cable run goes and often where the inverter lives. The consumer unit, because the system needs its own way and the board has to be fit to take it. Somewhere sensible for the battery, which is heavy, wants a stable temperature and should not be in a bedroom. And the incoming supply, because that governs what can be exported.

What happens on each day?

Scaffold goes up first, usually the day before. It is not optional and anyone quoting without it is either not doing the job properly or has left it out of the price to look cheaper.

The first working day is roof anchors and rails. Anchors go under the tiles onto the rafters, and this is the part that decides whether the roof still keeps water out in ten years. It is worth watching, because it is the step that gets rushed on a cheap install.

The second day is panels onto the rails, cabling into the loft, and the inverter and battery mounted and connected. The last stretch is the connection into the consumer unit, generation metering, testing, commissioning and showing you the app.

Then the scaffold comes down, which is often a few days later and outside the installer’s control.

What is MCS and why does it matter?

MCS is the standards scheme for small scale renewable installations. An MCS certificate is not a badge of quality for its own sake. It is the document your electricity supplier requires before it will pay you for the power you export under the Smart Export Guarantee.

In other words, an install without MCS certification can still work perfectly and still save you money on what you use, but you cannot be paid for the surplus. For most households the export payment is a meaningful part of the case for doing it at all.

Ask to see the installer’s MCS registration before you sign anything, and check the certificate arrives afterwards. We are MCS certified, which is why our solar and battery work comes with it.

Does the network operator have to agree?

Yes, and which way round depends on size. Smaller domestic systems can be installed and then notified to the Distribution Network Operator afterwards. Larger ones, and anything on a supply the network is already worried about, need permission before the work starts.

This is why an installer asks about your incoming supply and why a quote sometimes says the system size is subject to approval. On a rural single phase supply, which describes a lot of the villages round Olney, the network sometimes limits what you may export even though the roof could take more.

A good installer handles this application. You should not be filling in network forms yourself.

Should I add the battery now or later?

You can do either, and the honest answer depends on cash rather than on technology. What is worth knowing is that adding a battery later to a system that was not planned for one usually means a second inverter or a replacement, plus another visit and another set of testing.

If a battery is likely within a few years, say so at survey. Choosing a hybrid inverter now costs a little more and makes adding the battery later a much smaller job. That decision is nearly free today and expensive to reverse.

Questions we get asked about this