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 |
|---|---|---|---|---|---|---|---|
| Tue 30 Sep | £6.00 | £2.52 | £8.51 | £4.09 | 30.1 | 29.1 | 27.2 |
| Mon 29 Sep | £6.16 | £2.31 | £8.47 | £3.96 | 31.0 | 30.2 | 26.4 |
| Sun 28 Sep | £3.65 | £3.50 | £7.15 | £0.96 | 12.8 | 29.8 | 6.4 |
| Sat 27 Sep | £5.59 | £2.87 | £8.45 | £2.83 | 25.0 | 29.4 | 18.8 |
| Fri 26 Sep | £4.07 | £3.03 | £7.11 | £1.79 | 18.2 | 40.2 | 11.9 |
| Thu 25 Sep | £6.89 | £2.02 | £8.91 | £3.65 | 35.0 | 39.0 | 24.3 |
| Wed 24 Sep | £6.11 | £3.25 | £9.36 | £3.14 | 28.5 | 30.2 | 20.9 |
| Tue 23 Sep | £5.54 | £3.23 | £8.77 | £2.02 | 23.4 | 31.7 | 13.5 |
| Mon 22 Sep | £7.70 | £2.95 | £10.65 | £3.55 | 34.7 | 29.0 | 23.7 |
| Sun 21 Sep | £5.76 | £2.19 | £7.95 | £2.29 | 26.3 | 28.8 | 15.3 |
| Sat 20 Sep | £4.64 | £2.63 | £7.27 | £2.99 | 20.4 | 26.4 | 19.9 |
| Fri 19 Sep | £7.19 | £2.31 | £9.51 | £5.82 | 38.5 | 24.0 | 38.8 |
| Thu 18 Sep | £3.61 | £2.06 | £5.67 | £1.95 | 14.4 | 29.7 | 13.0 |
| Wed 17 Sep | £2.19 | £3.61 | £5.81 | £1.03 | 7.7 | 26.4 | 6.9 |
| Tue 16 Sep | £7.57 | £2.32 | £9.88 | £4.44 | 37.8 | 30.5 | 29.6 |
| Mon 15 Sep | £6.67 | £2.83 | £9.50 | £4.67 | 33.0 | 28.8 | 31.1 |
| Sun 14 Sep | £4.10 | £2.92 | £7.02 | £2.02 | 15.6 | 32.6 | 13.5 |
| Sat 13 Sep | £5.51 | £2.29 | £7.81 | £3.10 | 24.3 | 31.4 | 20.7 |
| Fri 12 Sep | £7.15 | −£0.48 | £6.67 | £3.67 | 36.2 | 32.7 | 24.5 |
| Thu 11 Sep | £6.35 | £2.02 | £8.36 | £4.34 | 30.7 | 30.4 | 28.9 |
| Wed 10 Sep | £3.46 | £2.00 | £5.46 | £2.30 | 13.6 | 28.6 | 15.4 |
| Tue 9 Sep | £7.68 | £1.95 | £9.63 | £6.40 | 40.8 | 29.0 | 42.7 |
| Mon 8 Sep | £7.47 | £1.97 | £9.44 | £6.30 | 39.5 | 27.4 | 42.0 |
| Sun 7 Sep | £6.82 | £2.02 | £8.84 | £5.52 | 35.2 | 26.2 | 36.8 |
| Sat 6 Sep | £8.37 | £2.23 | £10.61 | £7.39 | 46.6 | 26.2 | 49.3 |
| Fri 5 Sep | £7.65 | £2.05 | £9.70 | £5.78 | 39.8 | 27.0 | 38.5 |
| Thu 4 Sep | £6.84 | £1.97 | £8.81 | £4.88 | 33.5 | 27.1 | 32.5 |
| Wed 3 Sep | £4.12 | £2.00 | £6.12 | £2.15 | 16.6 | 28.0 | 14.3 |
| Tue 2 Sep | £4.18 | £1.98 | £6.16 | £2.25 | 16.7 | 27.9 | 15.0 |
| Mon 1 Sep | £7.61 | £1.59 | £9.20 | £5.41 | 36.9 | 27.5 | 36.0 |
Cumulative benefit
Running total across the selected window.
Thursday 4 September 2025, 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 |
|---|---|---|---|---|---|---|
| Tue 30 Sep | 29.10 | 26.62 | -8.5% | 27.24 | 25.06 | -8.0% |
| Mon 29 Sep | 30.17 | 27.83 | -7.8% | 26.41 | 24.01 | -9.1% |
| Sun 28 Sep | 29.75 | 25.70 | -13.6% | 6.43 | 2.94 | -54.2% |
| Sat 27 Sep | 29.35 | 26.17 | -10.8% | 18.84 | 15.96 | -15.3% |
| Fri 26 Sep | 40.19 | 26.73 | -33.5% | 11.92 | 8.84 | -25.8% |
| Thu 25 Sep | 38.99 | 26.82 | -31.2% | 24.34 | 25.15 | 3.3% |
| Wed 24 Sep | 30.20 | 27.84 | -7.8% | 20.92 | 18.15 | -13.2% |
| Tue 23 Sep | 31.65 | 27.59 | -12.8% | 13.45 | 10.05 | -25.3% |
| Mon 22 Sep | 29.04 | 26.05 | -10.3% | 23.66 | 20.99 | -11.3% |
| Sun 21 Sep | 28.81 | 26.41 | -8.3% | 15.29 | 18.35 | 20.0% |
| Sat 20 Sep | 26.41 | 24.18 | -8.4% | 19.93 | 18.47 | -7.3% |
| Fri 19 Sep | 24.00 | 23.14 | -3.6% | 38.79 | 37.51 | -3.3% |
| Thu 18 Sep | 29.67 | 26.99 | -9.0% | 13.02 | 10.56 | -18.9% |
| Wed 17 Sep | 26.40 | 22.38 | -15.2% | 6.86 | 3.64 | -46.9% |
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.