The heat pump
Due December 2026, after which the house won't burn any gas. We've done the sizing and the sums, but the radiators haven't been changed yet.
Install diary
From the first quote to the system running on its own, including the things that went wrong. Newest first; start at the bottom to read it in order.
Export starts paying, 110 days in
Between commissioning and today we sent 2,487 kWh to the grid for nothing (£298.50 at 12p) because there was no export MPAN to pay it into. Outgoing Octopus went live this morning at a flat 12p. The paperwork took months, and then Home Assistant and Predbat both needed a nudge before they saw it.
Leaving the fix five months early for Intelligent Octopus Go
A flat 24.5p is fine for a house that just uses electricity. Ours has a battery, a car and a heat pump arriving in December, so we paid the exit fee and moved to Intelligent Octopus Go: 8p overnight, 34.7p by day. Our cheap window also isn't the one on the advert.
Our first Axle event, and getting Predbat to see the next one coming
The battery ran its first paid grid event tonight: 5.5 kW out for an hour, £4.27 at £1/kWh. We also found that once a VPP event starts you can't touch the battery, so we changed Predbat to prepare for events in advance.
Signed up to Axle: getting paid for grid events
Same day as the inverter swap, we joined Axle's virtual power plant in events-only mode. It pays £1/kWh when the grid needs the battery, and because it settles through the smart meter it pays even though our export still isn't certified.
The correct inverter is fitted
Five days after we found the wrong unit had been fitted, the installer came back and swapped the 6 kW EC 6.0 SP for the EC 8.0 SP we ordered, well before export certification clears.
First tune-up: three small fixes from a config review
Three days in, we checked the whole automation stack against what's actually running on the box. Predbat is still in monitor mode, but the review found an automation bug and two settings to change before it takes control.
Home Assistant and Predbat are running
A day after install, the automation stack is up. Sigenergy, Octopus, Solcast and Predbat are all connected, running on a £50 Dell.
The wrong inverter: a 6 kW unit on the wall
We paid for a Sigenergy EC 8.0 SP. The installer has told us the unit fitted is the 6 kW model. This is what it costs us while we wait for the replacement.
Install day: 22 panels where 21 should have gone
The system went in on 4 June, and the installers found room for a 22nd panel on the roof, taking us from 9.98 to 10.45 kWp at no extra cost.