Energy savings
AlphaESS inverter joined to Octopus half-hourly meter reads and tariff prices.
Solar & battery installed by Heatable
£150 off solar £75 off a battery £50 off your Octopus bill referral
Where the benefit came from, by day
Solar and battery are separated by costing three worlds for every half hour — no panels and no battery, panels alone, then what actually happened — and taking the differences. A negative battery day is one that spent more storing energy than it gave back; it returns when the battery discharges. Export earnings sit inside the solar bar rather than beside it: the panels-alone world already sells its surplus, so that income is part of what solar is worth.
View as table
| Day | Solar | Battery | Total | of which export | Solar kWh | Imported | Exported |
|---|---|---|---|---|---|---|---|
| Thu 30 Apr | £9.72 | £2.80 | £12.52 | £4.08 | 53.5 | 18.0 | 34.0 |
| Wed 29 Apr | £9.20 | £2.25 | £11.45 | £4.42 | 55.2 | 14.5 | 36.9 |
| Tue 28 Apr | £7.75 | £1.50 | £9.25 | £3.05 | 43.3 | 15.9 | 25.5 |
| Mon 27 Apr | £8.83 | £1.99 | £10.83 | £4.09 | 53.9 | 15.6 | 34.0 |
| Sun 26 Apr | £9.71 | £0.97 | £10.68 | £3.59 | 53.0 | 16.7 | 29.9 |
| Sat 25 Apr | £9.38 | £2.22 | £11.60 | £3.55 | 52.3 | 19.9 | 29.6 |
| Fri 24 Apr | £10.15 | £2.31 | £12.46 | £4.40 | 59.8 | 22.2 | 36.7 |
| Thu 23 Apr | £9.59 | £3.60 | £13.19 | £4.15 | 57.3 | 19.6 | 34.6 |
| Wed 22 Apr | £10.02 | £2.67 | £12.70 | £4.20 | 59.3 | 24.3 | 35.0 |
| Tue 21 Apr | £7.55 | £2.91 | £10.47 | £1.01 | 36.2 | 23.1 | 8.4 |
| Mon 20 Apr | £7.82 | £3.03 | £10.85 | £2.37 | 40.9 | 20.1 | 19.7 |
| Sun 19 Apr | £9.31 | £2.14 | £11.45 | £3.44 | 51.6 | 17.3 | 28.7 |
| Sat 18 Apr | £8.78 | £1.63 | £10.42 | £2.81 | 46.5 | 19.8 | 23.4 |
| Fri 17 Apr | £8.85 | £1.51 | £10.36 | £3.25 | 48.6 | 22.0 | 27.0 |
| Thu 16 Apr | £6.03 | £2.08 | £8.11 | £0.57 | 23.9 | 31.5 | 4.8 |
| Wed 15 Apr | £3.72 | £3.52 | £7.24 | £0.59 | 13.3 | 36.5 | 4.9 |
| Tue 14 Apr | £5.32 | £3.30 | £8.62 | £0.63 | 19.2 | 34.5 | 5.3 |
| Mon 13 Apr | £4.85 | £3.11 | £7.97 | £0.67 | 17.4 | 32.4 | 5.5 |
| Sun 12 Apr | £5.04 | £3.22 | £8.25 | £0.77 | 18.2 | 32.3 | 6.4 |
| Sat 11 Apr | £4.16 | £3.50 | £7.66 | £0.65 | 14.9 | 31.5 | 5.4 |
| Fri 10 Apr | £4.23 | £2.35 | £6.58 | £0.59 | 15.2 | 25.0 | 4.9 |
| Thu 9 Apr | £2.79 | £2.10 | £4.89 | £0.48 | 10.4 | 24.2 | 4.0 |
| Wed 8 Apr | £3.01 | £1.63 | £4.65 | £0.49 | 11.0 | 30.6 | 4.1 |
| Tue 7 Apr | £4.05 | £3.50 | £7.55 | £0.68 | 14.5 | 31.4 | 5.6 |
| Mon 6 Apr | £6.98 | £3.18 | £10.16 | £0.61 | 25.2 | 38.3 | 5.1 |
| Sun 5 Apr | £5.53 | £3.27 | £8.80 | £0.62 | 19.8 | 38.6 | 5.1 |
| Sat 4 Apr | £4.80 | £3.33 | £8.13 | £0.57 | 17.3 | 49.7 | 4.8 |
| Fri 3 Apr | £3.11 | £3.82 | £6.93 | £0.42 | 11.2 | 45.0 | 3.5 |
| Thu 2 Apr | £4.89 | £3.50 | £8.40 | £0.64 | 17.5 | 48.0 | 5.3 |
| Wed 1 Apr | £4.72 | £3.30 | £8.01 | £0.63 | 16.9 | 39.3 | 5.2 |
Cumulative benefit
Running total across the selected window.
Thursday 23 April 2026, half by half
Energy arriving above the line, energy leaving below it, and the price you were paying on the same timeline. Charging through a cheap window and discharging through an expensive one is the shape to look for.
Inverter versus meter
The two measure at different points in the circuit and will never agree exactly. A few percent of drift is normal; a consistent double-digit gap means one feed is wrong and the solar/battery split should be treated with suspicion. The headline figures come from the meter either way.
| Day | Meter import | Inverter import | Drift | Meter export | Inverter export | Drift |
|---|---|---|---|---|---|---|
| Thu 30 Apr | 18.03 | 15.17 | -15.9% | 33.99 | 32.68 | -3.8% |
| Wed 29 Apr | 14.48 | 10.30 | -28.9% | 36.87 | 34.70 | -5.9% |
| Tue 28 Apr | 15.93 | 13.16 | -17.4% | 25.45 | 22.70 | -10.8% |
| Mon 27 Apr | 15.57 | 11.90 | -23.6% | 34.05 | 31.93 | -6.2% |
| Sun 26 Apr | 16.73 | 13.72 | -18.0% | 29.93 | 27.38 | -8.5% |
| Sat 25 Apr | 19.89 | 16.31 | -18.0% | 29.62 | 26.69 | -9.9% |
| Fri 24 Apr | 22.19 | 17.44 | -21.4% | 36.67 | 33.91 | -7.5% |
| Thu 23 Apr | 19.59 | 16.52 | -15.7% | 34.59 | 31.78 | -8.1% |
| Wed 22 Apr | 24.27 | 20.85 | -14.1% | 35.02 | 31.97 | -8.7% |
| Tue 21 Apr | 23.15 | 17.81 | -23.1% | 8.45 | 8.62 | 2.1% |
| Mon 20 Apr | 20.12 | 17.59 | -12.6% | 19.72 | 16.15 | -18.1% |
| Sun 19 Apr | 17.27 | 13.97 | -19.1% | 28.69 | 25.60 | -10.8% |
| Sat 18 Apr | 19.78 | 16.02 | -19.0% | 23.42 | 21.15 | -9.7% |
| Fri 17 Apr | 21.95 | 19.13 | -12.9% | 27.05 | 25.57 | -5.5% |
Return on investment
Measured across everything on record (7 Apr 2025 to 31 Aug 2026), not the range selected above — annualising a fortnight of summer would roughly double the apparent return. The yearly figure comes from the trailing twelve months, so it covers a full seasonal cycle.