The result
A 6.45 kWp in-roof solar and Tesla Powerwall system designed around a major home renovation.
Subsequent annual performance data recorded 5,370 kWh of generation against an original estimate of 5,432 kWh, with 94% of the solar electricity generated used on site. Whole-home backup was also provided through the Tesla Gateway.
At a glance
Location
Property
5-bed detached renovation
Installed
January 2025
System Size
6.45 kWp
Panels
14 × AIKO Neostar 460W
Battery
Tesla Powerwall 3
EST. Generation
5,432 kWh/year
Est. Year-one Benefit
Approx. £1,352
Est. Payback
7 years
The customer’s objective
The solar and battery system formed part of a wider home renovation. The homeowner wanted to reduce future electricity bills, become less dependent on grid electricity and build energy resilience into the property as part of the refurbishment rather than retrofitting it later.
Aesthetics were also important. The customer specifically wanted an in-roof solar installation that would sit neatly within the new roof design, together with whole-home backup capability.
The Phase Energy solution
Phase Energy designed a 6.45 kWp solar PV system using 14 AIKO Neostar 460W panels. The panels were installed as an in-roof system so that the array could be integrated into the roof as the renovation progressed.
The system was paired with a Tesla Powerwall 3 and Tesla Gateway, giving the property battery storage and whole-home backup capability. The Tesla system was also the homeowner’s preferred technology choice.
Why the system was designed this way
The roof layout and the architectural design of the renovation dictated how much solar could be accommodated. Phase Energy had to work around the shape of the new roof and the skylights while making the best use of the available area.
Using an in-roof system addressed the homeowner’s aesthetic requirement, allowing the solar installation to form part of the finished roof rather than sitting above it. The design therefore balanced energy generation with the visual and structural constraints already set by the renovation.
Installation
Because this was part of an active renovation, the work could not be completed as a conventional single-visit installation.
The solar team attended when the roof was ready so the in-roof array could be installed alongside the roofing work, with the electrical installation completed on a separate visit when that part of the project was ready.
This required Phase Energy to coordinate its work with the wider site programme rather than treating the solar installation as a standalone job.
Predicted energy and financial performance
At proposal stage, the system was estimated to generate 5,432 kWh per year and deliver a combined first-year financial benefit of approximately £1,352 from electricity savings and export income. The estimated payback period was seven years.
The original modelling was based on estimated household electricity use of around 20,000 kWh per year. It predicted that the system would cover approximately 25% of that demand and that around 95% of the solar generation would be used on site. These were proposal-stage estimates rather than guarantees of future performance.
Actual performance
Subsequent annual performance data provides a useful comparison with the original forecast. The system generated 5,370 kWh against a prediction of 5,432 kWh, while approximately 94% of the solar electricity generated was reported as being used on site.
| Metric | Predicted | Actual / Reported |
|---|---|---|
| Annual generation | 5,432 kWh | 5,370 kWh |
| Solar generation exported | 95% | 94% |
| Household electricity use | Approx. 20,000 kWh assumed | Approx. 30,000 kWh reported |
Actual household electricity use turned out to be significantly higher than had been assumed at proposal stage. This changes the proportion of total household demand that the system can cover, but the solar generation itself remained very close to the original annual forecast.
Whole-home backup
The Tesla Gateway was installed to provide whole-home backup capability. This was an important part of the customer’s aim to make the renovated property more resilient and less dependent on the grid.
More Home Solar Projects
See some more examples of happy client projects below
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Solar & Battery Installation in Tonbridge, Kent
Estimated to cover 66% of household electricity use and save £1,147 in year one.
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Solar & Tesla Powerwall Installation in Canterbury, Kent
Designed to cover around 80% of household electricity demand with whole-home backup.
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Solar & Tesla Powerwall Installation in Chesham, Buckinghamshire
Estimated to deliver £2,520 in year-one benefit with whole-home backup.