January Solar Generation and Export Numbers
January delivered a challenging start to the year, with a cold snap early in the month driving increased heat pump usage and higher daytime demand. To adapt, we switched to morning and afternoon battery charging, accounting for 12 charging slots, while suspending the batteries between 10pm and midnight to avoid inefficient cycling. January also included a single Octopus Saving Session on the 28th. Overall, this was the weakest solar generation month since the system was installed, reflecting deep winter conditions and limited daylight.
Solar generation for the month totalled 79.30 kWh, down 4.20 kWh compared to January last year’s 83.50 kWh. Solar contributed just 8% of total household consumption, which is in line with expectations for mid-winter but marks the lowest performance we’ve seen to date. There were no days where solar generation exceeded household consumption or grid imports, resulting in zero self-sustained days by either measure this month.
Total household consumption reached 951.70 kWh, reflecting the impact of colder weather and extended heat pump operation. Grid imports for the month were 988.90 kWh, reinforcing how heavily winter demand relies on the grid when solar availability is minimal.
Battery usage remained central to cost control. The batteries were charged with 595.20 kWh and discharged 554.80 kWh, showing sustained cycling to offset higher-priced daytime electricity. We used 356 grid charging slots during the month, while the batteries were suspended for 136 slots, largely to avoid charging during periods where the tariff offered no advantage.
The average grid charging slot cost this month was 15.08p per kWh. The cheapest charging slot was 14.62p, while the most expensive slot used reached 29.82p. Despite some higher-priced slots being unavoidable due to demand, the overall average remained well below the current price cap of 27.69p per kWh. The standing charge for the period was 48.389p per day.
The total cost of electricity imported on the Cosy tariff was £149.12. For comparison, importing the same energy on the standard tariff would have cost £273.83, while supplying the household entirely on the standard tariff would have resulted in a cost of £263.53. This represents a saving of £126.91 compared to standard tariff imports, and £116.61 compared to standard tariff household consumption.
Exports were slightly higher than December but still modest, as expected for January. We exported 14.70 kWh during the month, resulting in £2.21 of export savings. With limited generation, most solar energy was either consumed directly or used to support battery charging.
Looking at the wider picture, the average unit cost paid so far this year stands at 15.08p per kWh, significantly below the price cap average. Even in the most solar-constrained month, the combination of battery optimisation and the Cosy tariff continues to deliver substantial savings.
Overall, January highlights the system operating at its most grid-dependent. Solar contribution is at its lowest, battery strategy is critical, and savings are driven almost entirely by tariff selection and intelligent charging decisions. While generation was disappointing, the financial performance reinforces how effective the system remains, even under the toughest winter conditions.
According to the Octo-Aid app, this was the breakdown of our usage per rate.
Grid Usage by Rate (High, Mid and Low)
As solar panels output declines over the years I have added the previous years generation to the table at the bottom. Of course weather comes into it as well, but I thought it would be interesting to track. I have added this post that shows each year as a graph.
Octopus Energy bill
Octopus Watch Tariff Comparison Report. This does not include exporting
Best Solar Generation
| Date | kWh | |
|---|---|---|
| Generation | 26th May 2023 | 32.90 |
| Front generation | 14th June 2023 | 19.80 |
| Back generation | 7th June 2023 | 14.70 |
| Worst generation | 12th December 2022 | 0.20 |
Solar Generation January 2026
| Date | kWh | |
|---|---|---|
| Best generation | 28th | 5.40 |
| Best front generation | 28th | 4.10 |
| Best back generation | 30th | 1.50 |
| Worst generation | 9th | 0.70 |
| Worst front generation | 9th | 0.40 |
| Worst back generation | 9th | 0.30 |
Best Solar Export and Profit
| Date | kWh | Profit | |
|---|---|---|---|
| Exported kWh | 15th June 2024 | 22.20 | |
| Exported profit | 15th June 2024 | 22.20 | £3.15 (15p kWh) |
| Profit day | 14th April 2024 | 18.20 | £2.67 |
Solar/Battery Export and Profit January 2026
| Date | kWh | Income/Cost | |
|---|---|---|---|
| Best kWh export - Battery & Solar | 28th | 2.00 | |
| Best kWh export - Solar Only | 3rd | 0.30 | |
| Best export profit | 28th | 2.00 | £0.30 (15p kWh) |
| Cheapest Day | 24th | £3.79 |
The graph below shows the generation for both front and back panels
Total Solar Generation
The graph below shows generation, battery discharge, battery charging, export, import to use and consumption for 2026
Showing generation, battery discharge, battery charging, export, import to use and consumption for 2026
Overview for December
The graph below shows the generation for each day
Graph showing production for the month
The graphs below show the generation split between the front and back panels
Graph showing production for the front facing panels
Graph showing production for the back facing panels
The graphs below show the yearly generation split across both the back and front panels
Total Front Solar Generation
Total Back panel generation
Octopus Cosy
The costs shown here do include the standing charge. Any comparisons are compared to the unit cost if we were not on Cosy Octopus. There are two comparisons. One is the cost of what we imported from the grid for battery charging. The other is, the cost of the energy used by the house, house consumption.
January Grid Information
| Standard Tariff | 27.69p | ||
| Standing Charge | 48.39p | ||
| Cost from the grid | £ 149.12 (Cosy) | £ 273.83 (Standard) | |
| Savings including export | £126.91 | ||
| Exported | 14.70 kWh | £2.21 @ 15p kWh | |
| Charging slots used | 356 | ||
| Battery Suspended Slots | 136 | ||
| Average unit slot price | 15.08 | ||
| Cheapest slot | 14.62p | ||
| Most expensive slot | 29.82p | ||
| House consumed | 951.70 kWh | ||
| Solar generated 2026/2025 | 79.30 kWh | 83.50 kWh | |
| Battery Charged/Discharged | 595.20 kWh | 554.80 kWh | |
| Percentage generated by solar | 8% | ||
| Self Sustained Days 2026 (More solar than consumed) | 0 | ||
| Self Sustained Days 2026 (More solar than we imported) | 0 | ||
Here is the Octopus Watch report summary
Octopus Watch summary
Featured posts
Solar panel performance declines over the years. I thought it might be interesting to see how mine compares. Of course weather comes into it, but hopefully this will be a useful guide.