Solar Panels on New Build Homes: What Buyers Need to Know

New build homes in the UK increasingly come with solar panels as standard — not because developers are solar enthusiasts, but because building regulations require it. The systems installed are often minimal. Understanding what you've got, what it's worth, and how to improve it is essential for new build buyers.

Why New Builds Have Solar

The short answer: building regulations.

The 2021 Future Homes Standard and the updated Part L of the Building Regulations (effective June 2022) require all new homes to produce 75–80% less CO2 than homes built to the previous standard. Solar PV is one of the most effective ways developers can achieve this.

The SAP (Standard Assessment Procedure) calculation underpins this. SAP is the government's method for rating a home's energy performance. Developers must hit a target SAP score (the Target Emissions Rate, or TER), and solar PV improves the SAP score significantly.

The practical result: many new builds now arrive with a 2–3 kWp solar system as standard, regardless of whether the developer or buyer particularly wants one.

What Developers Actually Install

Developer-installed solar systems are sized for regulation compliance, not for maximum homeowner benefit. Typical characteristics:

• 2–3 kWp capacity — enough to meaningfully improve SAP scores, but small compared to an optimal residential system (4–6 kWp)
• Budget-range panels — tier 2 or tier 3 panels from less-known manufacturers, chosen on price
• Basic string inverter — usually a low-cost single-phase inverter with no battery management capability
• No battery provision — battery storage is rarely included in standard new build packages
• Minimal monitoring — basic generation monitoring, often without consumption data

This isn't necessarily a problem — a 2 kWp system still generates useful electricity. But it's worth knowing that what's installed is often the minimum viable system for compliance purposes, not an optimised setup.

SAP Calculations and What They Mean for You

The SAP calculation determines your home's EPC (Energy Performance Certificate) rating and its compliance with Part L. Solar PV feeds into the SAP calculation in several ways:

• It reduces the predicted annual CO2 output of the home
• It reduces the predicted energy cost
• It improves the EPC rating (often pushing a home from B to A)

A higher EPC rating is meaningful beyond compliance:

• Green mortgage products: Some lenders offer preferential rates for A or B rated properties
• Lower running costs: Higher-rated homes cost less to heat and power
• Resale value: EPC A rated homes command a modest premium in most markets

The SAP score assumes a certain generation profile from the panels — if you subsequently upgrade the system, the actual performance will be better than the rated EPC suggests.

Ownership and Warranties on Developer-Installed Solar

Once you complete on the property, the solar system is yours. This includes:

• Panels: Typically carry a 10-year product warranty and a 25-year performance warranty from the manufacturer
• Inverter: Typically 5–10 years warranty, depending on brand
• Workmanship: The installing company provides a workmanship warranty — usually 1–2 years (developer builds) to 10 years (quality installer)

Critical action: Ask your solicitor to obtain documentary confirmation that all warranties transfer to you on completion. Warranties on developer-installed systems should be assignable to the new owner, but this needs to be explicitly confirmed.

Also check:

• Which company installed the system (MCS certificate will show this)
• Whether the installer is still trading — warranty claims require the original installer or their insurer
• Whether the developer has any ongoing obligations for the system

The Inverter Question: What's Installed?

Before thinking about adding a battery, find out what inverter is in your new build. This determines your battery options.

If it's a string inverter (most common in developer installs): You can add a battery via AC coupling — the most practical route without replacing the inverter. See our AC vs DC coupling guide.

If it's a hybrid inverter: You can add a DC-coupled battery directly. Check which battery models are compatible with your specific inverter.

If it's microinverters (less common but some developers use Enphase): AC coupling is your only battery option. Enphase IQ Battery is the natural partner.

Common developer-installed inverters include Solis, Growatt, and Sofar — all string inverters. Battery can be added via AC coupling with no changes to the existing system.

Upgrading a New Build Solar System

Upgrading developer-installed solar is entirely normal and often worthwhile.

Adding More Panels

If your developer installed 2 kWp and your roof has space for 4 kWp, you can add panels. Things to check:

• Inverter capacity: The existing string inverter may not support additional panels without replacement or adding an additional inverter
• DNO limits: Most single-phase connections are limited to 3.68 kW export. Check if additional panels would push you over
• Roof space: New build roofs are often designed with solar in mind — there may be available south-facing space beyond what the developer used

Adding 2–3 panels to an existing 6-panel system is relatively straightforward. A larger addition may require inverter upgrade.

Adding Battery Storage

This is the most common upgrade for new build solar owners. A 2–3 kWp system generates significant electricity during the day — a battery lets you capture it for evening use rather than exporting it at 3–5p/kWh.

For a 2.5 kWp system generating around 2,100 kWh/year:

• Without battery: much of this is exported at SEG rate (3.3–5.2p/kWh)
• With a 5 kWh battery: significant proportion can be self-consumed at 24p/kWh value

A 5 kWh battery (e.g., GivEnergy 5.2 kWh, Solis/Pylon compatible) installed typically costs £3,000–5,000.

Replacing the Inverter with a Hybrid

If the developer-installed inverter is approaching end of warranty or you want DC-coupled battery options, replacing it with a hybrid inverter is an option. This is more disruptive and costs £1,200–2,000 for the hybrid inverter plus installation, but future-proofs the system.

This makes most sense if the original inverter is already failing or out of warranty.

What to Check When Buying a New Build With Solar

Before exchanging contracts:

1. Request the MCS certificate — confirms the system is properly registered
2. Ask for inverter brand and model — check the warranty period and battery compatibility
3. Ask for panel brand and model — check performance warranty (should be 25 years)
4. Check the SEG eligibility — is the system registered with an SEG supplier, or do you need to set this up?
5. Get warranty assignment in writing — panel, inverter, and workmanship warranties should all transfer
6. Check the generation meter reading — note the reading at completion so you can track production from day one

For the SEG (Smart Export Guarantee), you'll need to set up an export contract with an energy supplier. The MCS certificate is required to apply. Current rates range from 3.3p/kWh (basic tariff) up to 5.2p/kWh depending on the supplier and tariff you choose.

The Part L 2022 Changes: What They Mean Going Forward

The 2022 Part L update tightened energy performance requirements significantly. The next stage — the Future Homes Standard, expected fully in force by 2025–2026 — will tighten these further. New homes built under these standards will have:

• Better insulation and airtightness
• Heat pumps rather than gas boilers in many cases
• Larger solar systems in many developments
• EV charging provision

If you're buying off-plan (not yet built), it's worth asking the developer specifically which standard the home is being built to and what solar capacity is included. The trajectory is toward larger, better-specified systems as regulations tighten — but execution varies by developer.

Summary for New Build Buyers

• Your new build solar is a regulated feature, not a premium add-on — treat it as a starting point
• Get your MCS certificate and warranty documents before you move in
• Set up a SEG contract immediately to get paid for exports
• Check your inverter model before planning any battery addition
• Consider upgrading panel capacity or adding a battery once you've lived with the system for a year and understand your actual usage patterns

A 2–3 kWp new build system is useful but undersized for most families. Adding 2 kWp of panels and a 5 kWh battery typically turns a compliant-but-modest system into one that genuinely covers a significant portion of your electricity needs.

Share this article