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 |
|---|---|---|---|---|---|---|---|
| Fri 31 Oct | £1.78 | £4.20 | £5.98 | £0.47 | 6.0 | 61.6 | 3.2 |
| Thu 30 Oct | £4.13 | £3.36 | £7.49 | £0.63 | 14.2 | 50.2 | 4.2 |
| Wed 29 Oct | £1.19 | £3.75 | £4.94 | £0.58 | 4.0 | 51.8 | 3.8 |
| Tue 28 Oct | £4.02 | £3.24 | £7.26 | £0.76 | 16.4 | 45.1 | 5.1 |
| Mon 27 Oct | £3.54 | £3.79 | £7.33 | £0.70 | 12.8 | 38.4 | 4.7 |
| Sun 26 Oct | £4.06 | £4.88 | £8.94 | £0.65 | 15.4 | 34.1 | 4.4 |
| Sat 25 Oct | £4.45 | £2.73 | £7.18 | £1.48 | 15.6 | 51.2 | 9.8 |
| Fri 24 Oct | £3.93 | £3.37 | £7.31 | £1.41 | 14.5 | 43.2 | 9.4 |
| Thu 23 Oct | £2.84 | £4.39 | £7.24 | £0.57 | 9.6 | 28.4 | 3.8 |
| Wed 22 Oct | £4.81 | £2.41 | £7.22 | £0.73 | 20.4 | 23.4 | 4.9 |
| Tue 21 Oct | £3.89 | £2.47 | £6.36 | £0.59 | 16.3 | 31.3 | 3.9 |
| Mon 20 Oct | £2.24 | £3.70 | £5.94 | £0.63 | 7.9 | 33.9 | 4.2 |
| Sun 19 Oct | £1.55 | £3.30 | £4.85 | £0.53 | 5.3 | 40.5 | 3.5 |
| Sat 18 Oct | £3.26 | £4.20 | £7.46 | £0.59 | 11.1 | 21.6 | 3.9 |
| Fri 17 Oct | £3.94 | £1.99 | £5.94 | £0.58 | 16.3 | 24.3 | 3.9 |
| Thu 16 Oct | £4.41 | £2.72 | £7.13 | £0.59 | 18.1 | 30.6 | 4.0 |
| Wed 15 Oct | £3.62 | £3.90 | £7.53 | £0.68 | 13.4 | 32.4 | 4.6 |
| Tue 14 Oct | £2.27 | £3.65 | £5.92 | £0.53 | 7.8 | 33.0 | 3.5 |
| Mon 13 Oct | £3.04 | £3.87 | £6.92 | £0.56 | 10.3 | 33.2 | 3.7 |
| Sun 12 Oct | £5.40 | £2.43 | £7.83 | £0.70 | 21.0 | 31.9 | 4.7 |
| Sat 11 Oct | £3.17 | £3.60 | £6.77 | £0.68 | 11.3 | 31.8 | 4.5 |
| Fri 10 Oct | £2.04 | £4.16 | £6.20 | £0.50 | 6.9 | 35.3 | 3.3 |
| Thu 9 Oct | £5.69 | £2.40 | £8.09 | £3.21 | 26.2 | 30.1 | 21.4 |
| Wed 8 Oct | £3.36 | £2.59 | £5.94 | £1.42 | 13.7 | 30.0 | 9.5 |
| Tue 7 Oct | £4.39 | £3.04 | £7.43 | £2.60 | 19.7 | 30.1 | 17.3 |
| Mon 6 Oct | £5.77 | £3.21 | £8.97 | £3.50 | 27.5 | 28.3 | 23.4 |
| Sun 5 Oct | £6.12 | £3.16 | £9.28 | £2.38 | 25.7 | 26.7 | 15.9 |
| Sat 4 Oct | £6.28 | £1.16 | £7.44 | £2.04 | 27.2 | 30.7 | 13.6 |
| Fri 3 Oct | £1.04 | £3.69 | £4.73 | £0.45 | 3.5 | 29.4 | 3.0 |
| Thu 2 Oct | £5.10 | £1.63 | £6.73 | £2.74 | 22.0 | 32.4 | 18.3 |
| Wed 1 Oct | £4.17 | £2.19 | £6.37 | £2.55 | 18.2 | 29.9 | 17.0 |
Cumulative benefit
Running total across the selected window.
Sunday 5 October 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 |
|---|---|---|---|---|---|---|
| Fri 31 Oct | 61.56 | 59.25 | -3.7% | 3.16 | 0.72 | -77.2% |
| Thu 30 Oct | 50.18 | 46.65 | -7.0% | 4.20 | 0.92 | -78.1% |
| Wed 29 Oct | 51.81 | 48.60 | -6.2% | 3.84 | 0.81 | -78.9% |
| Tue 28 Oct | 45.06 | 41.25 | -8.5% | 5.09 | 1.25 | -75.4% |
| Mon 27 Oct | 38.43 | 34.38 | -10.5% | 4.67 | 1.05 | -77.5% |
| Sun 26 Oct | 34.06 | 36.24 | 6.4% | 4.35 | 0.92 | -78.9% |
| Sat 25 Oct | 51.19 | 47.31 | -7.6% | 9.84 | 6.04 | -38.6% |
| Fri 24 Oct | 43.21 | 38.77 | -10.3% | 9.41 | 5.20 | -44.7% |
| Thu 23 Oct | 28.41 | 25.25 | -11.1% | 3.83 | 0.86 | -77.5% |
| Wed 22 Oct | 23.37 | 21.14 | -9.5% | 4.85 | 1.45 | -70.1% |
| Tue 21 Oct | 31.28 | 26.19 | -16.3% | 3.91 | 0.57 | -85.4% |
| Mon 20 Oct | 33.93 | 30.50 | -10.1% | 4.20 | 0.61 | -85.5% |
| Sun 19 Oct | 40.46 | 37.23 | -8.0% | 3.53 | 0.70 | -80.2% |
| Sat 18 Oct | 21.61 | 18.05 | -16.5% | 3.90 | 0.54 | -86.2% |
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.