Solar Panels on New Build Homes

The proportion of new homes being built with solar panels is growing rapidly. Revised Part L building regulations, strengthened in 2022 and again in 2025, require new homes to achieve higher energy efficiency standards, and solar is one of the most cost-effective ways for developers to demonstrate compliance. In Wiltshire, Somerset, and South Gloucestershire — our core service area — most new build estates now include solar as standard on properties of three bedrooms and above.

However, there is an important distinction between solar systems designed to achieve regulatory compliance and solar systems designed to maximise the financial return for the homeowner. Developer-specified systems are typically the former. Understanding this distinction — and knowing what to check and what to upgrade — can make a significant difference to your energy bills from year one.

Battery storage is the upgrade that makes the most difference to a new build solar system. A developer-fitted system without battery storage typically exports 40–60% of its generation to the grid at SEG rates of 4–15p/kWh — electricity that cost you nothing to generate but is sold at a fraction of what you would pay to import it. A battery captures this excess generation and returns it to you in the evening at full avoided-import value (24–28p/kWh).

The most common battery addition to a new build is the Sigenergy 9.5kWh, added as an AC-coupled unit connected to the existing inverter. For new builds with a Sigenergy or Sigenergy hybrid inverter already fitted (increasingly common), the battery integration is simpler and cheaper — the inverter already has the battery management intelligence built in.

For new builds in the Wichelstowe, Tadpole Garden Village, Kingsdown (Swindon), and Mulberry Park (Bath) developments, we have carried out a number of battery retrofit installations. If you are in one of these areas, see our Swindon or Bath location pages for local case studies.

Some new builds are marketed as "solar-ready" without panels actually fitted. This typically means the developer has installed a conduit from the roof space to the consumer unit, a suitable south-facing roof orientation, and (sometimes) space reserved in the consumer unit for a generation meter. These provisions reduce the cost and disruption of a solar installation compared to a standard retrofit.

If your new build is solar-ready without panels, the installation cost is typically £300–£600 less than a standard retrofit, and the installation is faster (half to full day versus one to two days). A solar-ready home is an excellent candidate for an optimally specified system designed by an independent installer, rather than a developer's minimum-compliance package.

If your new build was fitted with a 3–4 panel system and your roof has capacity for 10–14 panels, expanding the system is usually technically straightforward — subject to the existing inverter's DC input headroom. The additional panels connect to the same inverter, the same mounting system, and the same monitoring platform. Installation time is typically half a day.

The financial case is compelling. Adding 6 panels (approximately 2.4kW) to a 3-panel system converts it from a minimal compliance installation to a properly-sized residential solar array. The additional output — approximately 2,000–2,400 kWh/year — at 24p/kWh avoidance value is £480–£580 per year. At a marginal installation cost of £2,000–£3,000, payback on the expansion is 4–6 years.

For a full breakdown of system sizes and costs, see our Wiltshire solar costs guide. To explore finance options including 0% APR, see our solar finance guide.