August Solar Generation and Export Numbers
Here is the overview for August 2025.
After record solar generation months from March to June this year, August was about average. The first four days were very poor. For most of the month the batteries were suspended between 4am and 7am. Solar generation starts later in the morning now. 4am to 7am is one of the three Cosy cheap rates. This is also when we heat the hot water. Hopefully this leaves the battery at a higher level and the battery will get to 100% and start exporting.
This month we generated 548.10 kWh and exported 13 out of 31 days. I count an exporting day as a day when we export more than 10p. We didn’t export on many consecutive days which points to the batteries not being fully charged. My system will charge from the grid if the batteries does not reach 100% for 7 consecutive days. This led to us using 48 half hours slots over August. We also had three free one hour Octopus Free Electricity Sessions. That accounts for six of those slots. Those free sessions saved us 97p
This year we have had 155 days where we generated more solar than we consumed, and 95 days more solar was generated than we imported from the grid. In August, 8 days the solar generated more than we imported, and of those 27 days more than we consumed.
According to the Octo-Aid app this was the breakdown of our usage per rate. Some of the mid rate would have been the free sessions.
Grid Usage by Rate (High, Mid and Low)
You can see the heat pump statistics here.
The worst generation day was the 16th with only 9.00 kWh. The best was the 8th when 26.00 kWh was generated.
The best export day was the 14th with 13.00 kWh.
As solar panels output declines over the years I have added the 2023 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 August 2025
| Date | kWh | |
|---|---|---|
| Best generation | 8th | 26.00 |
| Best front generation | 6th | 16.20 |
| Best back generation | 8th | 11.50 |
| Worst generation | 16th | 9.00 |
| Worst front generation | 16th | 3.90 |
| Worst back generation | 30th | 4.30 |
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 August 2025
| Date | kWh | Income/Cost | |
|---|---|---|---|
| Best kWh export - Battery & Solar | 9th | 5.70 | |
| Best kWh export - Solar Only | 14th | 13.00 | |
| Best export profit | 14th | 13.00 | £1.95 (15p kWh) |
| Cheapest Day | 10th | £-0.14 |
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 2025
Showing generation, battery discharge, battery charging, export, import to use and consumption for 2025
Generation
Overview for August
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, which is 26.010p per kWh. The standing charge was 45.42p
August Grid Information
| Standard Tariff | 25.010p | ||
| Standing Charge | 45.42p | ||
| Cost from the grid | £ 13.81(Cosy) | £ 45.88(Standard) | |
| Savings including export | £41.49 | ||
| Exported | 62.80 kWh | £9.42 @ 15p kWh | |
| Charging slots used | 48 | ||
| Agile plunge slots used | 0 | ||
| Average unit slot price | 13.60p | ||
| Cheapest slot | 12.756p | ||
| Most expensive slot | 26.01p | ||
| House consumed | 612.70 kWh | ||
| Solar generated 2025/2024 | 548.10 kWh | 559.40 kWh | |
| Battery Charged/Discharged | 290.70 kWh | 285.50 kWh | |
| Percentage generated by solar | 89% | ||
| Self Sustained Days 2025 (More solar than consumed) | 155 | ||
| Self Sustained Days 2025 (More solar than we imported) | 95 | ||
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.