Your MCS certificate should reach you within 30 days of your system being commissioned, and without it no supplier will pay you for exported electricity under the Smart Export Guarantee. That deadline sits with MCS rather than with your installer, and it applies to certified domestic installations across the UK. The month after commissioning is when the certificate, the grid paperwork and the export application all need to happen, and none of the three is automatic.
Two documents follow a domestic installation, and neither affects whether the system works. It has been generating and storing electricity since the day it was commissioned. What the paperwork does is prove the installation exists, to the specification it was sold at, to your energy supplier today and to whoever buys your home later.
The first is your MCS certificate, and it is the one that matters most, because your Smart Export Guarantee application depends on it. Under the redeveloped MCS installer scheme it must be raised within 30 calendar days of commissioning.
The second is written commissioning confirmation from your Distribution Network Operator, and what form it takes depends on the size of your inverter. Where your system needed permission before installation, keep the approval itself as well the confirmation. Unfortunately, this step is what tends to cause delays, as the DNO typically takes 2-3 weeks to raise the commissioning confirmation. In periods of high demand, the DNOs can take north of 6-8 weeks to return the confirmation, and unfortunately, installers can't speed this up, it's in the hands of your DNO.
Spirit Energy issues both together as soon as we can, but certainly within two to three weeks of installation, so you hold the pair well inside the deadline and can apply for export payments straight away.
Under the redeveloped MCS scheme, your installer must buy an MCS approved financial protection product on your behalf. It funds remediation where something is wrong with the installation and you cannot get it resolved through the original installer, including where they have gone bankrupt, retired, or simply refuse to put the work right. It covers failures in design, not only workmanship.
Two details make it worth chasing. Cover runs for a minimum of six years, against a previous standard minimum of two, which brings it into line with your rights under the Consumer Rights Act for goods that are not of satisfactory quality or fit for purpose. And the excess you can be charged is capped at £250, so a claim on a system that cost fifteen thousand pounds cannot be priced out of reach by the excess alone.
Ask which product covers your installation, who provides it, when the cover starts, and where the documentation is.
What is owed to your Distribution Network Operator after commissioning depends on the size of your inverter, and this is where most homeowners get confused about who they should be chasing.
Up to 3.68 kW per phase, which is 11.04 kW on a three phase supply, you can install first and notify the network operator afterwards. Above that threshold, permission has to be granted before installation. So if you have a larger system, the approval already existed before the scaffolding went up and there is nothing outstanding from the DNO now. What follows commissioning is confirmation of what was actually fitted, not a decision you are waiting on.
That approval is worth reading rather than filing, because it is where any export limit will be stated. Across Spirit Energy's installations in southern England, DNO confirmations take around three weeks in normal periods and up to eleven when the DNO operators are busy, and in the Berkshire area around our office roughly 8 in 10 households are approved for 11 to 12 kW of generation but limited to exporting 7 or 8 kW. A limit like that constrains what you can add to the system later, so it needs to be written down rather than remembered.
Note that every supply is different, and only a full G99 assessment with your DNO will inform you of the maximum generation and export potential.
You cannot be paid for exported electricity until your supplier issues an export MPAN, and the application has to be made by you. Your installer cannot do this part for you. Suppliers only accept export applications from the account holder, and your installer has no involvement in your supply contract
Every supplier will ask for your MCS certificate. That is the direct link between the paperwork deadline above and money arriving in your account, and it is the reason chasing the certificate is worth your time rather than a box-ticking exercise.
Two things worth knowing before you apply. You do not have to take your export tariff from the supplier who provides your import electricity, and the two can be held separately. And where you have a battery installed, the import rate usually matters more to your annual position than the export rate does, because a well configured battery shifts a substantial share of your consumption into cheaper overnight periods. Compare the two together rather than chasing the highest headline export figure.
Expect the first two weeks to look wrong.
Modern battery systems learn a household's consumption pattern before they optimise against it. Across Spirit Energy's residential installations the consistent observation is that behaviour settles into a sensible rhythm after roughly 2 weeks. Before that, charge and discharge decisions can look arbitrary, and homeowners frequently conclude something is faulty when nothing is.
The one thing that reliably makes this worse is intervening. Every time settings are changed in the app, the algorithm has a fresh pattern to learn and the settling period extends. Leave it alone for two weeks, then judge it.
Confirm the app connects reliably, first of all. Intermittent connection in week one tends to indicate a network or configuration issue on site, which is far cheaper to resolve while the installation is fresh.
Then watch the system across several days of different weather. You are building a baseline, not assessing performance. A single overcast week tells you nothing.
Compare what you see against the annual generation estimate in your quotation. That figure comes from a standard MCS methodology using historical irradiance data for your postcode, so it is an annual average rather than a monthly promise. Judging a system against it in February is not a fair test.
Finally, confirm you can locate the isolators and know the shutdown procedure. If you were not on site for the handover demonstration, ask your installer for the app guide relevant to your system and walk through it once.
Who is my named contact, and when does that change? Most installers hand you from a project manager to a support function at some point after installation. Find out when, and what the route is afterwards.
What does the workmanship warranty cover, and for how long? Product and workmanship warranties are separate things and run for different lengths. Panels typically carry a 25 year product warranty, batteries commonly ten, and inverters often between five and twelve depending on manufacturer. The installer's workmanship warranty is a third, separate cover, and it is the one most likely to be shorter than you assume. Ask for all three in writing, with the start date for each.
What does the system need from me over its life? For most rooftop installations in the UK the honest answer is very little, but you should hear it from the people who installed it rather than assume it.
Is there anything unusual about my installation? Split arrays, restricted export limits, unusual roof types or software limited inverters all have consequences later, particularly if you ever want to expand the system. Better to have that written down now than to reconstruct it from memory in a decade.
None of this takes long, and the month after commissioning is the only point at which all of it is easy. The people who installed the system still have it fresh, the documents are still being generated, and nobody has moved on. Get the certificate, the DNO approval and the answers to those four questions into one folder while that is true, and the next twenty five years ask very little of you.