Notes from the workshop.

Our pilot homes range from a one-bedroom flat in Rosemount to a draughty granite detached house in Cults. Between November and March each logged its store temperature, heat delivered and electricity bought, every half hour.

Across all fifty, 84% of the electricity used for heating and hot water was bought in the cheap hours. The best home managed 96%; the worst, a large house with an undersized prototype, managed 61%. That house now has a bigger store.

These are averages from a small pilot, not a promise for your home. We will publish the full data set, anonymised, with our next research note.

Two new install teams started this month, one based out of Westhill and one covering Stonehaven and Newtonhill. If you reserved with a postcode in AB32 or AB39, our surveyors are working through the queue in order.

Ellon, Inverurie and Banchory are next. You can check your postcode on the reservation page at any time.

Detached homes in the north east can use more than 70 kWh of heat on a cold day, which is more than a Heatloop 28 can shift on its own. The Heatloop 40 adds a wider store, a 9 kW element and faster hot water.

It shares every part of its controls and hydraulics with the smaller models, which keeps it simple to service. Indicative pricing is on the technology page.

After two years of building stores by hand in a unit too small to turn a pallet truck in, we have moved into a former pipe-coating workshop in Dyce. It has room for 2,000 units a year on a single shift.

The test bay runs every finished store through a full charge and discharge before it leaves. We are hiring for the line; see the careers page.

A Heatloop melts and freezes its cells about once a day. To be confident a store will last, we cycle sample cells much faster in a rig that heats and cools them with oil, logging capacity every hundred cycles.

Our current cell design has passed 10,000 cycles with less than 4% loss of capacity in testing. We also open up returned cells from pilot homes to check that the field matches the lab.

We have raised £6.5m in a seed round led by Firthside Ventures, with Cairnmoor Capital and Brackwater Climate Fund. Dagny Pirie of Firthside joins our board.

The money goes into three things: the production line in Dyce, our install teams, and the research that makes each store a little better than the last.

Until now, each Heatloop charged fully in the cheapest hours every night. The new schedule reads the next day’s forecast and how the home used heat last week, so mild days need less charging and cold snaps get a top-up after lunch.

In the pilot it reduced the heat bought at day rates by about a fifth. The update installed itself overnight in all fifty homes.

A hot water cylinder stores heat well but takes a lot of space for the energy it holds. Bricks heated to several hundred degrees hold more, but need careful insulation and safety design. A phase-change material stores most of its energy as it melts, at a single moderate temperature.

For a store that sits in a cupboard and feeds radiators at around 60°C, melting at 58°C is the sweet spot. That is why every Heatloop is built around it.

For seven days in January the temperature in Aberdeen did not climb above freezing. Every pilot home kept its usual comfort settings and none ran short of hot water.

Eleven homes needed some direct heating at day rates on the coldest evenings. We have since adjusted their schedules, and in two cases recommended a larger store.