September 2025 updates
September Electric:
I managed to maintain a 17.6% Peak/Off-Peak ratio, which down on last month’s 6.98%.
There were a quite a few days that were overcast, and on the rest I managed to have only minimal peak usage.
Electricity costs for the month of September: £149.85 for 2025, £151.93 for 2024 and £507.08 for 2023 – better than last year, and still way better than the year before.
Electricity demand for the month of September: 1709kWh for 2025, 1717kWh for 2024 and 1734kWh for 2023.
The saving for this year was around £2.00 less for 8kWH less usage.
The off-peak/peak/SC values for September were £0.07/0.24393/0.488 for 2024 vs £0.07/£0.2896/0.4542 for 2025, which are the same as last month.
This can also be seen in the month on month usage vs cost graphs:
September Solar:
Actual production for September far exceeded the forecast for every day, often by way more than double, I had some internet issues on the 20th, so I have no forecast data for that day.
The various arrays produced the following levels of energy: Garage 215.22kWh, Office 178.01kWh, East 114.79kWh, West 137.77kWh for a total of 645.79kWh which is quite a drop from last month
A reasonable month for solar production, I also managed to export 130.45kWh for a total saving of £19.57.
The import costs of £149.85 less the export savings of £19.57 means my net cost for September was £130.29 for 1709kWh of demand making my average rate £.0764/kWh.
September Gas:
Gas costs for the month of September: £30.54 for 2025, £25.86 for 2024 and £255.28 for 2023 (more crazy numbers).
Gas usage for the month of September: 468kWh for 2025, 356kWh for 2024 and 350kWh for 2023.
£5.00 more than last year, 30% more gas consumed and on the Octopus Gas Tracker tariff vs the Octopus Standard Gas Tariff, so similar to last month.
Gas prices remained about the same this month, I would have paid a lot more had I still been on the Octopus Standard Tariff, which was £0.0699 per kWh for September £40.03 ((427 * 0.0699) + 10.18sc) or an additional £12.06 for the month.
The heating was off for the entire month, so gas was only used for heating the hot water.
Again all visible in the usage vs cost graphs.
There were a number of ‘free electricity sessions this month that again had some quite wildly different savings
01/09 I used an additional 12.04kWh and saved £0.85 (12.04 * 0.07/kWh) – this was an ‘off-peak’ saving because the car was plugged in and Octopus gave me a charging session that overlapped with the ‘free electricity’
06/09 I used an additional 12.92kWh and saved £0.91 (12.92 * 0.07/kWh) – this was an ‘off-peak’ saving because the car was plugged in and Octopus gave me a charging session that overlapped with the ‘free electricity’
07/09 I used an additional 12.87kWh and saved £3.73 (12.87 * 0.2896/kWh) – much better, as this was a ‘peak rate’ saving
11/09 I used an additional 8.45kWh and saved £2.45 (8.45 * 0.2896/kWh) – much better, as this was a ‘peak rate’ saving
15/09 I used an additional 11.51kWh and saved £1.85 (11.51 * 0.2896/kWh) – much better, as this was a ‘peak rate’ saving
18/09 I used an additional 9.75kWh and saved £2.83 (9.75 * 0.2896/kWh) – much better, as this was a ‘peak rate’ saving
For most of the sessions I also discharged the batteries for an hour or so beforehand so I would be able to charge them to a decent level during the ‘free’ periods.
Total additional saving of £12.62 (0.85+0.91+3.73+2.45+1.85+2.83) which brings my electricity costs for the month down even further from £130.29 to £117.67