December 2025 updates
December Electric:
I managed to maintain a 29.11% Peak/Off-Peak ratio, which is an improvement on last month’s 32.67%.
This is largely due to the purchase of some additional battery units – more on that later.
Much of the month was overcast, and/or had minimal sunshine, but an average UK December.
Electricity costs for the month of December: £226.31 for 2025, £284.18 for 2024 and £536.66 for 2023 – slightly better than last year, and less than half of the year before.
Electricity demand for the month of December: 1656Wh for 2025, 1751kWh for 2024 and 1815kWh for 2023.
The cost for this year was around £58.00 less for 96kWH less usage.
The off-peak/peak/SC values for December were £0.07/0.26716/0.488 for 2024 vs £0.07/£0.29198/0.4879 for 2025, peak is slightly down, but the standing charge is up.
This can also be seen in the month on month usage vs cost graphs:
December Solar:
Actual production for December far exceeded the forecast for every day, often by way more than double.
The various arrays produced the following levels of energy: Garage 43.87kWh, Office 40.33kWh, East 14.74kWh, West 23.36kWh for a total of 122.30kWh which is another drop from last month
A relatively poor month for solar production, I managed to export 14.52kWh for a total saving of £2.18.
The import costs of £226.13 less the export savings of £2.18 means my net cost for December was £223.959 for 1656kWh of demand making my average rate £0.1348/kWh.
December Gas:
Gas costs for the month of December: £135.61 for 2025, £198.60 for 2024 and £172.58 for 2023.
Gas usage for the month of December: 2914kWh for 2025, 3116kWh for 2024 and 2538kWh for 2023.
£63.00 less than last year, for only slightly less gas usage.
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 December £212.36 ((2914 * 0.0699) + 8.67sc) or an additional £76.75 for the month.
The heating was on for the entire month, I also include a temperature graph to show how gas usage for heating was also affected by the outside temperatures.
Again all visible in the usage vs cost graphs.
There were no Saver Sessions or Free Energy Sessions this month.
I made use of some Black Friday sales codes to purchase four EcoFlow Stream AC Pro batteries.
These are intended as ‘add-on’ batteries for a balcony solar system that uses the EcoFlow Stream Ultra that has 4 x MPPT connections each of which can have a 500W solar panel connected to it.
Each one has a 1.92kWh capacity and they can be daisy-chained together to create a larger battery. You can have up to 6 EcoFlow Stream units connected within your property, I am unsure if you can potentially have more if they are not actually connected to each other, but used as independent (sets of) items.
If you intend to ‘back feed’ electricity into your house, then in the UK, these must be connected via a fused spur. If however you only use them to ‘feed’ appliances that are plugged into their output ports, then you can simply plug them into a socket.
I have 3 of these feeding my office network cabinet and my iMac Pro. I charge them at night on cheap off-peak electricity and they are usually exhausted by around 14:00.
3 x 1.92 = 5.76kWh, however they are set to reserve the last 5% and there are a number of ’round trip’ losses which means that in reality I only get around 4.75kWh useable.
The daily draw is around 13kWh, 4.75 of which is supplied by the batteries and 8.25 from ‘the grid’, the off-peak hours will be at £0.07/kWh, the peak hours may be from my other batteries or may actually be from the grid, either way, I am running around 14 of the 24 hours at the cheap rate or £0.98, the remaining 10 hours are at peak rate, or from my Enphase solar/battery installation.
This means that I am saving an additional 8.5 hours at £0.07 vs £0.29 per kWh – £0.59 (8.5 *0.07) vs £2.47 (8.5 * 0.29) or an additional daily saving of £1.88
I was intending to put the fourth battery in the loft to feed my loft network rack, however the unit decided to ‘brick’ itself during install and I am awaiting a replacement unit.