The problem: a cold cul-de-sac with a gas habit
Bananzia’s shared ground-loop trial started with a measurable headache: 24 homes on one cul-de-sac, 21 gas boilers, and four properties that lost heating whenever the street’s pressure dropped on freezing mornings. A 2023 survey found 62% of annual gas use went on space heating, with the sharpest demand between 6am and 8am. The takeaway was simple: a heat pump retrofit would fail if it ignored the street’s simultaneous morning peak.
The cause: oversized boilers and no shared design
The boilers had been sized home by home, often at 18–24 kW, even though the street’s average heat loss after basic fabric upgrades was closer to 6 kW per property. That oversizing masked poor controls: thermostats were set to 22°C in hallways, radiators were unbalanced, and nobody had modelled the street as a system. The result was a set of individually rational choices that produced an inefficient whole.
The solution: a shared loop, sequenced demand, and honest controls
The bananzia design team proposed a 120 kW shared ground-loop array feeding individual 5–7 kW heat pumps in each home. A 12,000-litre thermal store buffered the morning peak, while flow restrictors and smart thermostats staggered hot-water reheating from 5am to 9am. The key detail was not the hardware but the sequence: three homes per 20-minute window, verified by a street-level controller.
- Fabric first: lofts and cavity walls were upgraded before heat pumps were commissioned.
- Measured sizing: each home received a room-by-room heat-loss survey, not a boiler-replacement shortcut.
- Resident controls: households kept room setpoints but lost the ability to fire a second heating source during peak hours.
The result: lower peaks, fewer surprises
Over the first heating season, the trial recorded a 38% reduction in peak electrical demand compared with a modelled all-electric baseline without storage. Mean internal temperature stayed within 0.6°C of the residents’ setpoints, and two homes needed radiator upgrades after commissioning. The takeaway is that shared infrastructure works only when the street’s operating rhythm is designed as carefully as its pipework.
What other streets can copy
Start with a measured peak, not a headline efficiency figure. Bananzia’s most transferable lesson is procedural: survey every home, model the street together, and write the sequencing rules into the commissioning checklist. A shared ground loop can cut carbon, but without demand management it simply moves the bottleneck from gas pipes to electricity wires.
