Generic case study. We do not name the building, the address or the owners — the value is the cabling strategy, the metering, the OZEV paperwork and the DNO sequence.
The brief
A 1970s detached house in Bath, divided in the 1990s into 2 self-contained flats with separate front doors, separate energy meters but a shared 60 A communal incomer. Two off-street parking bays, one per flat, both on the same gravel driveway. Both households had committed to electric vehicles and wanted their own dedicated 7 kW charger so neither was dependent on the other. The brief: install both chargers, claim both OZEV EVHS grants, and meter each charger separately so EV electricity could be billed clean of the household supply if either flat went on the rental market.
What we did
- Site survey + load assessment. Existing 60 A communal incomer measured under load. Two 32 A EV circuits would have pushed the supply over its rated capacity — an upgrade was non-negotiable.
- DNO notification submitted for the 60 A to 100 A upgrade. DNO attended within their booked window to upgrade the cut-out and tails.
- Two OZEV EVHS grant applications prepared in parallel, one per flat, each tied to its own eligible vehicle and dedicated parking bay. Both approved.
- Two Hypervolt Home 3 Pro 7 kW chargers installed, one per flat, mounted on the boundary wall above each bay with the cable tail running clear of the gravel.
- Type A 30 mA RCBO with DC fault detection on each charger circuit. EV chargers always go on Type A — never Type B — per BS 7671 and EVSE manufacturer guidance. Type B is for specific industrial DC scenarios, not domestic EV charging.
- MID-approved kWh sub-meter on each charger feed so each flat's EV usage is metered independently of the household.
- BS 7671 inspection-and-test on both circuits, EVSE function test, NAPIT-format Electrical Installation Certificate per circuit, Part P notified through NAPIT to local building control.
- OZEV claim submitted with photos, serials, sub-meter readings and certs per flat.
The board, per flat
| Component | Spec |
|---|---|
| Charger | Hypervolt Home 3 Pro 7 kW |
| Circuit | 32 A radial, 6 mm² T+E + SWA garden run |
| Protection | Type A 30 mA RCBO with DC fault detection |
| Sub-meter | MID-approved kWh sub-meter, sealed |
| PEN-fault | Built-in PEN-loss device (no earth rod) |
| Communal incomer | 100 A switched isolator (DNO upgrade) |
The result
Both flats now charge independently, each at full 7 kW, with no risk of tripping the communal incomer. Each flat owns its EV electricity bill. OZEV grant funding (up to £350 per charger) was claimed successfully on both, taking real cash off the customer total. The shared mains is now future-proofed at 100 A, leaving headroom for a possible heat-pump retrofit on either flat without going back to the DNO.
Who it's for
Owners or landlords of multi-flat conversions, terraced rentals, HMOs or coach-house conversions where one supply feeds 2 or more dwellings and at least one occupant wants an EV charger. The pattern travels: separate sub-meter per charger so the bill is clean, OZEV EVHS per flat where eligible, DNO uplift where the existing incomer can't carry the load.
Why this approach. Most flat conversions assume the EV charger is a "one charger, share the cable" problem. It isn't. With separate metering and a properly sized communal incomer, every flat gets a real, full-rate, independently-billed charger — and OZEV money gets claimed twice, not once.
Also see: EV chargers, EV charger grants guide, commercial EV fleet case study.