Skip to main content

Semi-detached cottage

PV panels, battery & EV charging point
Download Printable Case Study (PDF)


Age/Period: Mid- to late-19th century
Type: 2-storey, semi-detached cottage
Years in residence: 3
No. Bedrooms: 3
Wall type: Solid wall & cavity. Main house: Bath stone ashlar and random rubble. Extension: Ashlar stone outer leaf, inner blockwork leaf.
Area: Batheaston, BA1

Key Features

Loft Insulation
Double glazing

Energy-efficient appliances and lighting

Roof-mounted solar PVs & battery


Eleanor’s home is located in a semi-rural setting on the eastern slopes of Batheaston village. The house is just off a steeply sloping narrow lane and is part of a pair of small semi-detached cottages occupying an elevated/exposed position above that lane. The house is separated from the lane by a bank of vegetation. It is believed that the pair of cottages originally formed one dwelling. The long axis of the building runs north–south, with an open aspect to the south. Eleanor’s cottage was extended in approx. 2010, prior to her moving in. The main dwelling is of solid wall construction with a loft. The extension is of cavity wall construction with first-floor rooms extending to underside of roof (i.e. no loft), tiled with concrete double roman tiles. Eleanor doesn’t believe there is much insulation in the extension walls, if any. The two-storey extension is highly glazed on the south elevation and is particularly draughty at ground-floor level throughout year; the living room is also prone to overheating in summer.

The house has an electric boiler. Eleanor sought changes to the house to support EV (electric vehicle) charging, looking for an ecological, pragmatic solution that aligned with her technical background. This led to installation of PV panels. The house is also used as home office.


Insulation / Loft Insulation

The loft is boarded out for storage with limited insulation underneath. There is potential to increase the loft insulation levels, taking care to maintain the eaves ventilation.

Double Glazing

The house already had double glazing fitted, however Eleanor has raised concerns about draughts and overheating, particularly from the large set of glazed doors in the living room.

Appliances & lighting

The household uses low-energy lighting throughout.

PV Panels

The need for an electric vehicle charging point led to PV panels and battery interest. They were procured through local authority initiative ‘Solar Together – Bath & North East Somerset Council‘. This initiative encourages interested parties to register, and when adequate number of projects are collated a contractor is selected via a reverse auction.

Nine PV panels were installed, split across east and west roofs, two years ago. The system includes a Growatt inverter, battery & web interface.

The web interface is a monitoring platform for users. It shows self-consumption, generation, storage, export and energy trends. Eleanor’s energy supplier is Octopus. The EV charging point was arranged through the ‘Octopus Go’ tariff.

While currently on a good tariff, Eleanor says it was difficult to access because charge point supplier have limited tariffs available to them.

Prior to PV installation, the property rated D with B potential. PV installation is likely to have improved the property to C rating.

Energy usage is approximately 10-15 kWh per day at upper end. Annual electrical consumption is 4,644kWh, with solar generation of 3,550kWh.

From data accessed via Growatt app, PV + battery measures equate to 710 KgCO2 saving per year.

PV installation, together with visibility of energy usage has driven behavioural change, e.g. nighttime EV charging, dishwasher use and clothes washing. The intelligent system means the EV is charged only when the house battery is full, i.e. the energy needs of the house take priority. Benefits are monthly cost savings, and Eleanor believes the house is now more marketable/desirable.

Other Measures

In response to the draughts, thick curtains, blinds and carpets have been installed. In colder months, a bio-ethanol burner is used to raise the temperature of the living space a few degrees. Solar light installed over bin store. Draught excluders to be considered.

Future Plans

Eleanor is generally happy with things as they are now, as for two-thirds of the year PVs provide enough energy for all the hot water, space heating and car charging. Eleanor queries whether a heat pump would be appropriate as the electrical heating cost provided by grid supply is relatively expensive.

As an early adopter of PV, Eleanor has some reservations: she believes that one would need to live in property for a number of years to see financial payback. Eleanor is interested in community energy schemes at scale as an alternative model for financial investment in renewables, instead of individual house measures. Additional measures also considered are insulation of extension and draught proofing the living space.


Infinity Renewables