Solar by Numbers · journeyInstall diary for a UK solar and battery project: Sigenergy, Predbat, Octopus Agile, and real daily performance data.https://solarbynumbers.co.uk/Our first Axle event, and teaching the system to see the next one cominghttps://solarbynumbers.co.uk/journey/2026-06-16-first-axle-event/https://solarbynumbers.co.uk/journey/2026-06-16-first-axle-event/Tonight the battery ran its first paid grid event: a steady 5.5 kW out for an hour, £4.27 of help to the grid at £1/kWh. It also taught us that once a VPP event starts there's no touching the battery, so we rewired Predbat to prepare for events in advance instead of scrambling during them.Tue, 16 Jun 2026 00:00:00 GMTSigned up to Axle: getting paid for grid eventshttps://solarbynumbers.co.uk/journey/2026-06-10-axle-vpp-signup/https://solarbynumbers.co.uk/journey/2026-06-10-axle-vpp-signup/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 earns even though our export still isn't certified.Wed, 10 Jun 2026 00:00:00 GMTThe right inverter is on the wallhttps://solarbynumbers.co.uk/journey/2026-06-10-the-right-inverter/https://solarbynumbers.co.uk/journey/2026-06-10-the-right-inverter/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 actually ordered. The race against export certification is won.Wed, 10 Jun 2026 00:00:00 GMTFirst tune-up: three small fixes from a config reviewhttps://solarbynumbers.co.uk/journey/2026-06-07-first-tune-up/https://solarbynumbers.co.uk/journey/2026-06-07-first-tune-up/Three days in, we audited the whole automation stack against what's actually running on the box. Predbat is still in training, but the review caught a subtle automation bug and two settings worth changing before it takes control.Sun, 07 Jun 2026 00:00:00 GMTThe brain is live: Home Assistant and Predbat take overhttps://solarbynumbers.co.uk/journey/2026-06-05-the-brain-is-live/https://solarbynumbers.co.uk/journey/2026-06-05-the-brain-is-live/One day after install, the automation stack is running. Sigenergy, Octopus, Solcast and Predbat are all talking to each other on a £50 Dell.Fri, 05 Jun 2026 00:00:00 GMTPlot twist: there's a 6 kW inverter on the wallhttps://solarbynumbers.co.uk/journey/2026-06-05-wrong-inverter/https://solarbynumbers.co.uk/journey/2026-06-05-wrong-inverter/We paid for a Sigenergy EC 8.0 SP. The installer has just told us the unit fitted is the 6 kW model. Here's what that actually costs us while we wait for the fix.Fri, 05 Jun 2026 00:00:00 GMTInstall day: 22 panels where 21 should have gonehttps://solarbynumbers.co.uk/journey/2026-06-04-install-day/https://solarbynumbers.co.uk/journey/2026-06-04-install-day/The system went in on 4 June, and the installers squeezed a 22nd panel onto the roof. We went from 9.98 to 10.45 kWp for free.Thu, 04 Jun 2026 00:00:00 GMT