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 |
|---|---|---|---|---|---|---|---|
| Mon 31 Aug | £0.00 | £0.00 | £0.00 | £0.00 | 0.0 | 0.1 | 0.0 |
| Sun 30 Aug | £4.85 | −£0.74 | £4.10 | £1.38 | 30.1 | 0.8 | 11.5 |
| Sat 29 Aug | £2.36 | £0.36 | £2.73 | £0.17 | 12.3 | 1.1 | 1.4 |
| Fri 28 Aug | £5.95 | £0.28 | £6.23 | £3.79 | 40.1 | 1.3 | 31.6 |
| Thu 27 Aug | £4.32 | £0.21 | £4.52 | £2.22 | 28.1 | 1.3 | 18.5 |
| Wed 26 Aug | £6.81 | £0.14 | £6.95 | £3.58 | 43.8 | 1.0 | 29.8 |
| Tue 25 Aug | £7.18 | £0.46 | £7.64 | £4.55 | 50.4 | 1.0 | 37.9 |
| Mon 24 Aug | £7.79 | £0.36 | £8.15 | £3.76 | 47.2 | 1.7 | 31.3 |
| Sun 23 Aug | £7.55 | £0.89 | £8.44 | £2.70 | 41.2 | 1.6 | 22.5 |
| Sat 22 Aug | £7.50 | £0.29 | £7.79 | £3.93 | 47.2 | 2.0 | 32.7 |
| Fri 21 Aug | £6.59 | £0.60 | £7.19 | £3.36 | 41.5 | 1.5 | 28.0 |
| Thu 20 Aug | £6.33 | £0.11 | £6.43 | £2.82 | 38.5 | 1.3 | 23.5 |
| Wed 19 Aug | £4.85 | £0.65 | £5.50 | £2.23 | 31.6 | 1.1 | 18.5 |
| Tue 18 Aug | £4.48 | £0.51 | £4.98 | £1.72 | 27.0 | 0.8 | 14.3 |
| Mon 17 Aug | £5.86 | £0.31 | £6.17 | £2.54 | 36.5 | 0.7 | 21.2 |
| Sun 16 Aug | £5.45 | £0.49 | £5.93 | £1.87 | 32.1 | 0.8 | 15.6 |
| Sat 15 Aug | £6.26 | −£0.18 | £6.07 | £2.17 | 40.8 | 0.9 | 18.1 |
| Fri 14 Aug | £7.40 | −£0.47 | £6.93 | £3.55 | 48.8 | 0.8 | 29.6 |
| Thu 13 Aug | £8.27 | £1.41 | £9.67 | £3.97 | 52.0 | 0.6 | 33.1 |
| Wed 12 Aug | £7.84 | £0.21 | £8.06 | £4.39 | 53.9 | 0.7 | 36.6 |
| Tue 11 Aug | £7.90 | £0.28 | £8.18 | £5.06 | 55.8 | 0.8 | 42.2 |
| Mon 10 Aug | £8.32 | £0.14 | £8.47 | £4.32 | 54.4 | 1.0 | 36.0 |
| Sun 9 Aug | £6.86 | −£1.83 | £5.03 | £2.14 | 52.8 | 1.3 | 17.8 |
| Sat 8 Aug | £8.64 | £0.79 | £9.43 | £5.05 | 56.1 | 1.0 | 42.1 |
| Fri 7 Aug | £8.39 | −£0.19 | £8.20 | £5.41 | 58.3 | 1.0 | 45.1 |
| Thu 6 Aug | £8.32 | £0.67 | £8.99 | £4.28 | 49.3 | 1.3 | 35.7 |
| Wed 5 Aug | £6.50 | −£1.87 | £4.63 | £1.87 | 42.8 | 4.6 | 15.6 |
| Tue 4 Aug | £6.79 | £0.14 | £6.93 | £2.95 | 40.8 | 0.9 | 24.6 |
| Mon 3 Aug | £7.48 | £0.64 | £8.12 | £3.84 | 47.0 | 0.9 | 32.0 |
| Sun 2 Aug | £8.80 | £0.33 | £9.14 | £4.78 | 56.2 | 1.1 | 39.8 |
| Sat 1 Aug | £9.04 | £0.22 | £9.27 | £5.16 | 59.4 | 1.1 | 43.0 |
Cumulative benefit
Running total across the selected window.
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 |
|---|---|---|---|---|---|---|
| Mon 31 Aug | 0.06 | 0.59 | 883.3% | 0.00 | 20.58 | — |
| Sun 30 Aug | 0.84 | 0.60 | -28.5% | 11.50 | 18.30 | 59.1% |
| Sat 29 Aug | 1.11 | 0.92 | -16.8% | 1.41 | 2.61 | 85.4% |
| Fri 28 Aug | 1.34 | 0.98 | -26.8% | 31.59 | 31.49 | -0.3% |
| Thu 27 Aug | 1.26 | 0.94 | -25.6% | 18.50 | 18.42 | -0.4% |
| Wed 26 Aug | 1.03 | 0.78 | -24.0% | 29.84 | 29.77 | -0.2% |
| Tue 25 Aug | 1.04 | 0.69 | -33.3% | 37.91 | 37.78 | -0.3% |
| Mon 24 Aug | 1.67 | 1.05 | -37.1% | 31.32 | 30.89 | -1.4% |
| Sun 23 Aug | 1.60 | 0.98 | -38.9% | 22.49 | 22.12 | -1.6% |
| Sat 22 Aug | 1.96 | 1.26 | -35.8% | 32.72 | 32.24 | -1.5% |
| Fri 21 Aug | 1.50 | 0.92 | -38.8% | 28.02 | 27.66 | -1.3% |
| Thu 20 Aug | 1.28 | 0.76 | -40.8% | 23.51 | 23.23 | -1.2% |
| Wed 19 Aug | 1.10 | 0.65 | -41.0% | 18.55 | 18.42 | -0.7% |
| Tue 18 Aug | 0.77 | 0.48 | -37.5% | 14.32 | 14.22 | -0.7% |
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.