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 |
|---|---|---|---|---|---|---|---|
| Wed 31 Dec | £2.64 | £3.34 | £5.98 | £0.17 | 9.0 | 70.5 | 1.1 |
| Tue 30 Dec | £2.87 | £3.58 | £6.45 | £0.16 | 9.7 | 74.7 | 1.1 |
| Mon 29 Dec | £1.13 | £3.56 | £4.68 | £0.23 | 3.8 | 68.0 | 1.5 |
| Sun 28 Dec | £0.80 | £3.64 | £4.44 | £0.28 | 2.7 | 61.8 | 1.8 |
| Sat 27 Dec | £2.58 | £3.53 | £6.11 | £0.13 | 8.7 | 87.6 | 0.9 |
| Fri 26 Dec | £1.87 | £3.59 | £5.46 | £0.15 | 6.3 | 98.5 | 1.0 |
| Thu 25 Dec | £2.64 | £3.61 | £6.25 | £0.18 | 8.9 | 112.4 | 1.2 |
| Wed 24 Dec | £2.78 | £3.65 | £6.43 | £0.19 | 9.4 | 87.3 | 1.3 |
| Tue 23 Dec | £0.41 | £4.27 | £4.69 | £0.32 | 1.4 | 74.8 | 2.1 |
| Mon 22 Dec | £1.60 | £3.44 | £5.04 | £0.43 | 5.4 | 58.3 | 2.9 |
| Sun 21 Dec | £1.04 | £3.46 | £4.50 | £0.34 | 3.5 | 61.6 | 2.3 |
| Sat 20 Dec | £2.59 | £3.64 | £6.23 | £0.41 | 8.9 | 59.9 | 2.7 |
| Fri 19 Dec | £2.53 | £3.85 | £6.38 | £0.48 | 8.8 | 53.8 | 3.2 |
| Thu 18 Dec | £0.18 | £4.02 | £4.20 | £0.28 | 0.6 | 72.4 | 1.9 |
| Wed 17 Dec | £1.63 | £3.76 | £5.39 | £0.25 | 5.5 | 63.8 | 1.7 |
| Tue 16 Dec | £1.07 | £4.05 | £5.11 | £0.37 | 3.6 | 53.8 | 2.4 |
| Mon 15 Dec | £0.39 | £3.92 | £4.31 | £0.32 | 1.3 | 65.6 | 2.1 |
| Sun 14 Dec | £1.51 | £3.73 | £5.24 | £0.36 | 5.1 | 73.2 | 2.4 |
| Sat 13 Dec | £2.75 | £3.79 | £6.54 | £0.47 | 9.3 | 54.5 | 3.1 |
| Fri 12 Dec | £0.80 | £3.79 | £4.59 | £0.40 | 2.7 | 55.0 | 2.6 |
| Thu 11 Dec | £1.54 | £3.68 | £5.22 | £0.36 | 5.2 | 67.9 | 2.4 |
| Wed 10 Dec | £2.23 | £3.63 | £5.85 | £0.62 | 7.7 | 44.2 | 4.1 |
| Tue 9 Dec | £0.44 | £3.85 | £4.30 | £0.41 | 1.5 | 52.2 | 2.7 |
| Mon 8 Dec | £0.77 | £3.81 | £4.58 | £0.40 | 2.6 | 57.1 | 2.6 |
| Sun 7 Dec | £0.39 | £3.73 | £4.11 | £0.45 | 1.3 | 51.1 | 3.0 |
| Sat 6 Dec | £1.90 | £3.67 | £5.56 | £0.54 | 6.4 | 48.5 | 3.6 |
| Fri 5 Dec | £2.10 | £3.96 | £6.06 | £0.35 | 7.1 | 61.0 | 2.4 |
| Thu 4 Dec | £0.83 | £3.66 | £4.49 | £0.29 | 2.8 | 62.3 | 1.9 |
| Wed 3 Dec | £1.70 | £3.56 | £5.26 | £0.50 | 5.9 | 54.0 | 3.3 |
| Tue 2 Dec | £2.30 | £4.04 | £6.34 | £0.50 | 7.9 | 51.0 | 3.3 |
| Mon 1 Dec | £0.24 | £3.89 | £4.13 | £0.29 | 0.8 | 58.4 | 1.9 |
Cumulative benefit
Running total across the selected window.
Friday 2 January 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 |
|---|---|---|---|---|---|---|
| Wed 31 Dec | 70.52 | 67.69 | -4.0% | 1.12 | 0.39 | -65.0% |
| Tue 30 Dec | 74.70 | 72.76 | -2.6% | 1.08 | 0.25 | -76.8% |
| Mon 29 Dec | 68.02 | 65.71 | -3.4% | 1.52 | 0.32 | -78.9% |
| Sun 28 Dec | 61.81 | 59.12 | -4.3% | 1.84 | 0.35 | -81.0% |
| Sat 27 Dec | 87.56 | 85.42 | -2.4% | 0.87 | 0.16 | -81.5% |
| Fri 26 Dec | 98.47 | 96.42 | -2.1% | 0.97 | 0.24 | -75.3% |
| Thu 25 Dec | 112.42 | 110.28 | -1.9% | 1.17 | 0.36 | -69.2% |
| Wed 24 Dec | 87.28 | 85.11 | -2.5% | 1.26 | 0.28 | -77.8% |
| Tue 23 Dec | 74.79 | 72.59 | -2.9% | 2.10 | 0.82 | -61.0% |
| Mon 22 Dec | 58.27 | 55.38 | -5.0% | 2.88 | 1.16 | -59.7% |
| Sun 21 Dec | 61.57 | 58.23 | -5.4% | 2.28 | 0.47 | -79.4% |
| Sat 20 Dec | 59.87 | 56.59 | -5.5% | 2.72 | 0.84 | -69.1% |
| Fri 19 Dec | 53.75 | 50.88 | -5.3% | 3.20 | 0.77 | -76.0% |
| Thu 18 Dec | 72.41 | 71.08 | -1.8% | 1.85 | 0.46 | -75.2% |
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.