Eco Build to achieve an A-Rated EPC with a Flat Roof Solar System & Battery Storage | January 2026


Project Overview

This project completed the final stage of a modern eco-build, helping the homeowner achieve an A-rated EPC. With the property already designed to be highly energy-efficient, the goal was to add renewable technology that would significantly reduce reliance on the grid, lowering costs and future-proofing the home against rising energy prices.

Because the property features a flat roof, we designed a solar solution that works with the building rather than against it, delivering strong performance without compromising the roof structure or the clean, modern look of the home.

The Solar & Battery System

The system was carefully sized to match the household’s electricity usage while allowing for future flexibility.

  • 18kW solar PV system

  • 40 high-efficiency 450W solar panels

  • K2 D-Dome flat roof mounting system

  • Sigenergy hybrid inverter

  • Sigenergy 18.08kWh battery storage

In simple terms, the solar panels generate electricity during the day, the battery stores any unused energy, and the home then uses that stored power in the evening or overnight, reducing the need to buy electricity from the grid.

The system is expected to generate around 11,721 kWh of electricity each year, comfortably covering the home’s annual usage and supporting the A-rated EPC outcome 


Why a Flat Roof D-Dome System?

Flat roofs are increasingly common on eco-builds, and the K2 D-Dome system is one of the most reliable solutions available.Key benefits include:

  • No drilling into the roof, protecting the waterproof membrane
  • Ballasted design, meaning the system is held in place by weight rather than fixings
  • Optimised panel angles, helping the system generate energy throughout the day
  • Low-profile, modern appearance, ideal for contemporary homes
This approach ensures excellent performance while maintaining the integrity and lifespan of the roof.Energy Usage & Day-to-Day BenefitsThe household’s estimated annual electricity use is 8,000 kWh. With the addition of battery storage, the system allows the homeowner to use far more of their own solar energy rather than exporting it.
  • Up to 68% energy independence from the grid
  • Estimated annual bill savings: ~£2,129
Any surplus energy not used or stored can be exported back to the grid, generating additional income through the Smart Export Guarantee.

Payback & Long-Term Value

  • Total system cost: £20,752
  • Estimated payback period: 8 years and 6 months
  • Estimated lifetime bill savings of £65,739, resulting in projected net savings of £44,985 after installation costs
For an eco-build aiming for the highest EPC rating, this installation not only improves energy performance but also adds long-term value and resilience to the property 


Why EPC Ratings Matter
EPC ratings are becoming increasingly important for both homeowners and landlords, affecting property value, mortgage eligibility, and rental compliance. Improving your EPC rating can lower running costs and make your property more attractive to buyers or tenants. If you’d like to understand how solar and battery storage can help improve your rating, read our full guide to EPC ratings here: Understanding EPC Ratings


Thinking about improving your EPC rating or adding solar to your home?


Whether you’re completing an eco-build, upgrading a flat roof property, or simply looking to reduce energy bills, our team can design a system that works around your home and your energy use. With over 16 years of experience and tailored, no-obligation quotes, we’ll show you exactly how solar and battery storage could improve your efficiency, savings, and EPC rating. Get in touch today to start your journey toward a more energy-efficient home.