Solar on new build homes

What to ask before exchange

1. Capacity in kWp, and the number and rating of modules.
2. Which roof plane, and its orientation and pitch. A north or east plane on a plot where a south one exists is a decision somebody made.
3. The modelled annual generation, and the assumptions behind it.
4. Who installed it, and are they MCS certified?
5. When do I receive the MCS certificate, the building regulations compliance certificate and the DNO notification?
6. What inverter, at what AC rating, and is there headroom to add panels later?
7. Is there an export meter and export MPAN, or do I arrange that myself?
8. What warranties, from whom, and are they transferable to me as first purchaser?

Ask in writing. Under section 50 of the Consumer Rights Act 2015, what you are told about the service can become a term of the contract — see mis-selling.

Why the estimate may tell you less than usual

MIS 3002 prescribes a performance estimate including self-consumption calculated to MGD 003. But it allows the self-consumption sections to be omitted where the occupancy archetype is not known — and on a new build, before anyone has lived there, it is not.

So a new build estimate can legitimately give you generation without telling you what it is worth. That is not evasion; it is the standard acknowledging that nobody knows how you will live yet.

What it means for you: do that half yourself once you know your own pattern. Our self-consumption page sets out MGD 003’s figures, and the rooftop calculator takes generation and a self-consumption range and gives you the spread.

Adding to it later

Usually possible, with three checks:

Roof space and orientation. Our orientation figures will tell you what a second plane is worth — south-east or south-west costs only about 6% against due south, while a north plane at 35° gives 54%.

Inverter headroom. The existing inverter’s AC rating may or may not accommodate more panel capacity. A higher DC:AC ratio is normal, but there is a limit.

Notification. Adding capacity changes the registered capacity, which may move you across the G98 threshold of 16 A per phase — 3.68 kW single-phase. A modification affecting technical capability must be notified to the network operator, and may trigger compliance testing.

The paperwork, again

The handover pack matters more on a new build than a retrofit, because you were not the customer of the installer — the developer was. That makes you one step removed from everyone who holds a document about your own roof.

Get the MCS certificate, the building regulations compliance certificate and the DNO notification in your hands. You will need the first for a SEG tariff, and a buyer’s conveyancer will ask for all three when you sell.