Building regulations now push developers towards fitting solar on new homes, so the question on a new-build is rarely “should I have panels?” and more often “which of these three packages?” The contractor’s menu will typically run from a small system that gets the house through the regulations to a larger one with a battery, and the prices step up with each. A buyer who has just signed for the house, and is being asked to decide on the upgrade in a week, is in the weakest possible position to judge it.
Why the developer’s options are different from a normal quote
On an existing house, you choose the installer, the size and the kit. On a new-build you usually get none of those choices. The developer’s contractor has already decided the panel and inverter models, the roof slope it goes on is fixed by the plot, and the smallest option exists because the energy calculation for the house needed it, not because it suits you.
That has three consequences.
The base system is often too small to matter. A system sized to pass a regulation can be two or three panels. It will make a dent in your bills, but not the one the brochure implies.
The upgrade prices do not scale honestly. Moving from the base system to a larger one should cost roughly the price of the extra panels, because the scaffolding, the inverter and the electrician’s visit are already paid for. Compare the price difference between options with the cost of the extra kWp. If the step up costs as much per kWp as the base system, the margin is on the upgrade.
The battery is where the money goes. The top option usually bundles a battery. Whether that makes sense depends on your evening usage and your tariff, not on the solar, and a developer’s contractor has no way of knowing either. The guide on whether a home battery makes sense has the four numbers to work through.
An example: three options, one answer
A recent client was buying a new-build in the south-east and had been offered three PV packages by the developer’s contractor, with about £12,000 at stake across the choices. He is an electrical engineer, so the specification sheets held no mystery for him. What he did not have was a way to tell what each option would actually produce on that roof, in that orientation, against what the household was likely to use.
The answer came from modelling each option: the yield for that plot and roof, the share of it the household would use rather than export, the savings at a realistic tariff, and the payback for each package side by side. One option was clearly the right size for the house; the step up to the next was paying a lot for generation that would mostly be exported. He chose with the numbers in front of him rather than the brochure, which is all a second opinion is meant to give you.
The questions to put to the contractor
- What size is each option in kWp, and what annual generation is assumed for this plot? The orientation of your roof is known, so the estimate should be specific, not a national average.
- What is the price of each step up, per extra kWp? Ask for the difference, not the totals.
- Can the battery be added later, by anyone? A hybrid inverter makes that easy; a plain string inverter may need replacing to add storage. If the answer is “only our battery, only now”, the pressure is the product.
- Where does the inverter go, and is there a cable route for an EV charger? Both are cheap to get right before the plasterboard goes on and expensive after.
- Who do I ring when it faults, and for how long? On a new-build the workmanship warranty may sit with the developer, the contractor or the home warranty provider. Get the answer in writing.
- What paperwork do I get at handover? The MCS certificate, the DNO notification and the commissioning sheet. Without the first you cannot register for export payments.
What to do next
Write down what your household uses in a year in kWh, from your current bills, and set it against the generation figure for each option. If the base option covers a third of it and the top option covers more than all of it, the answer is usually in the middle, and the battery is a separate decision. If you would like the full comparison on your plot and your usage, with the three options side by side, that is a Second Opinion at the home rate, and two working days is usually fast enough for a developer’s deadline.