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
Saved on bills is the gap between what you would have paid and what you actually paid. Total benefit is that saving plus the export payments.
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 Jul | £7.12 | £0.55 | £7.67 | £4.01 | 48.2 | 0.8 | 33.4 |
| Thu 30 Jul | £8.41 | £0.34 | £8.75 | £4.33 | 52.8 | 0.8 | 36.1 |
| Wed 29 Jul | £8.95 | £0.85 | £9.80 | £5.32 | 58.4 | 0.9 | 44.4 |
| Tue 28 Jul | £8.19 | −£0.35 | £7.84 | £3.99 | 51.9 | 1.3 | 33.3 |
| Mon 27 Jul | £8.23 | £1.81 | £10.04 | £5.19 | 57.5 | 1.1 | 43.2 |
| Sun 26 Jul | £7.54 | £0.01 | £7.55 | £2.57 | 43.4 | 1.0 | 21.4 |
| Sat 25 Jul | £9.35 | £1.59 | £10.94 | £5.15 | 59.8 | 1.2 | 42.9 |
| Fri 24 Jul | £7.81 | −£0.56 | £7.25 | £2.68 | 44.9 | 1.5 | 22.3 |
| Thu 23 Jul | £6.33 | £0.91 | £7.24 | £2.93 | 40.5 | 1.8 | 24.4 |
| Wed 22 Jul | £6.53 | £0.55 | £7.08 | £2.60 | 41.0 | 1.4 | 21.6 |
| Tue 21 Jul | £6.08 | £1.93 | £8.01 | £2.67 | 36.9 | 1.7 | 22.2 |
| Mon 20 Jul | £10.04 | £0.71 | £10.76 | £5.46 | 64.3 | 2.0 | 45.5 |
| Sun 19 Jul | £9.07 | £0.72 | £9.79 | £5.99 | 62.9 | 1.4 | 49.9 |
| Sat 18 Jul | £8.79 | −£0.22 | £8.57 | £5.67 | 61.4 | 1.0 | 47.3 |
| Fri 17 Jul | £8.00 | £0.09 | £8.09 | £5.09 | 55.5 | 1.4 | 42.5 |
| Thu 16 Jul | £9.58 | −£0.24 | £9.34 | £5.30 | 64.7 | 0.9 | 44.2 |
| Wed 15 Jul | £9.76 | £1.20 | £10.96 | £5.54 | 66.0 | 1.2 | 46.1 |
| Tue 14 Jul | £11.88 | −£0.12 | £11.77 | £5.20 | 67.1 | 0.9 | 43.3 |
| Mon 13 Jul | £9.62 | −£0.52 | £9.10 | £5.43 | 67.4 | 1.0 | 45.3 |
| Sun 12 Jul | £9.19 | −£0.66 | £8.53 | £5.44 | 68.3 | 0.9 | 45.3 |
| Sat 11 Jul | £9.56 | £0.39 | £9.95 | £6.14 | 66.7 | 0.8 | 51.2 |
| Fri 10 Jul | £9.40 | £0.78 | £10.18 | £5.83 | 62.9 | 0.8 | 48.6 |
| Thu 9 Jul | £9.28 | £0.19 | £9.47 | £5.94 | 63.6 | 0.8 | 49.5 |
| Wed 8 Jul | £10.20 | £0.42 | £10.63 | £5.22 | 63.5 | 0.7 | 43.5 |
| Tue 7 Jul | £9.02 | £0.51 | £9.53 | £5.70 | 62.3 | 0.9 | 47.5 |
| Mon 6 Jul | £9.73 | £0.57 | £10.30 | £5.77 | 64.5 | 0.9 | 48.1 |
| Sun 5 Jul | £10.40 | £0.23 | £10.64 | £5.17 | 63.1 | 1.1 | 43.1 |
| Sat 4 Jul | £9.27 | £0.52 | £9.79 | £4.50 | 57.2 | 1.2 | 37.5 |
| Fri 3 Jul | £10.08 | −£0.07 | £10.01 | £6.48 | 68.5 | 1.1 | 54.0 |
| Thu 2 Jul | £9.40 | −£0.01 | £9.38 | £5.58 | 62.2 | 0.9 | 46.5 |
| Wed 1 Jul | £7.17 | −£1.03 | £6.14 | £2.29 | 43.4 | 1.8 | 19.1 |
Cumulative benefit
Running total across the selected window.
Thursday 26 March 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 |
|---|---|---|---|---|---|---|
| Fri 31 Jul | 0.77 | 0.57 | -26.0% | 33.42 | 33.39 | -0.1% |
| Thu 30 Jul | 0.79 | 0.52 | -34.2% | 36.11 | 36.04 | -0.2% |
| Wed 29 Jul | 0.94 | 0.72 | -23.7% | 44.36 | 44.26 | -0.2% |
| Tue 28 Jul | 1.27 | 0.86 | -32.0% | 33.29 | 33.15 | -0.4% |
| Mon 27 Jul | 1.09 | 0.72 | -34.1% | 43.24 | 43.04 | -0.5% |
| Sun 26 Jul | 0.99 | 0.47 | -52.5% | 21.41 | 21.19 | -1.0% |
| Sat 25 Jul | 1.22 | 0.68 | -44.1% | 42.93 | 42.52 | -0.9% |
| Fri 24 Jul | 1.49 | 0.86 | -42.2% | 22.33 | 21.95 | -1.7% |
| Thu 23 Jul | 1.80 | 0.94 | -47.9% | 24.44 | 23.78 | -2.7% |
| Wed 22 Jul | 1.44 | 0.39 | -72.9% | 21.64 | 20.95 | -3.2% |
| Tue 21 Jul | 1.74 | 0.96 | -44.9% | 22.25 | 21.51 | -3.3% |
| Mon 20 Jul | 1.97 | 1.00 | -49.1% | 45.50 | 44.82 | -1.5% |
| Sun 19 Jul | 1.44 | 0.88 | -39.1% | 49.88 | 49.50 | -0.8% |
| Sat 18 Jul | 1.04 | 0.82 | -21.0% | 47.26 | 47.24 | -0.1% |
Return on investment
Measured across everything on record (7 Apr 2025 to 2 Sep 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.