July Solar Generation and Export Numbers
July was an exceptionally hot month in the UK, featuring multiple heatwaves which meant we had to use the air conditioning units overnight. We ran the mobile air conditioner for two nights at the start of the month before a fixed unit was installed on the 10th. Remarkably, we smashed our all-time generation record by 60 kWh and beat our previous July record by an incredible 171.90 kWh. This is particularly impressive as production typically begins to decline during this month, but the conditions allowed us to produce a significant surplus of energy despite the increased demand for cooling.
Looking at the raw numbers, we produced a whopping 792.50 kWh this month, which is a significant jump from the 672.50 kWh we generated in June. Even though our household consumption rose to 753.40 kWh (compared to 692.30 kWh last month), our system still managed to cover 105.19% of our house usage, surpassing the 97.14% we achieved in June. We saw 17 days where solar output exceeded household consumption and a staggering 28 days where it exceeded what we imported from the grid—a clear improvement over last month's 13 and 22 days respectively. This proves that our system remains incredibly reliable even when we are running high-drain appliances. The fixed air conditioning unit added 41.81 kWh to this months consumption.
We continued our strategy of charging overnight at the cheap 8p kWh rate to ensure we export at the higher rate during the day which is 12p kWh. To achieve this, we utilised 201 charging slots (each 30 minutes in length), which is slightly fewer than the 225 used last month. We also saw an increase in suspended slots to 171—up from 135 in June—where the battery is suspended and not discharging because it was more cost-effective to use the grid. This strategic adjustment helped us maintain a lower average grid slot cost of 9.74p, compared to last month's 10.61p. We charged the battery a total of 380.10 kWh and discharged 388.40 kWh, ensuring we remained efficient while managing our energy storage during these peak summer temperatures.
Our grid import dropped significantly this month to 534.20 kWh, down from 637.70 kWh in June, thanks to the continued efficiency of the Intelligent Octopus Go (IOG) tariff. Our total imported electricity bill on IOG was just £52.03, which is a fantastic reduction from the £67.66 we paid last month.
This shows how effectively our smart management keeps us shielded from high energy prices. Furthermore, our average unit cost for the year has improved to 12.85p, down from 13.37p in June. We even had a brilliant day on 06/07/2026 when our electricity costs were -64p, narrowly beating last month's best of -63p!
The data from July highlights how proactive management and the right tariff can turn a hot summer into a cost-effective success. We achieved massive savings compared to what we would have paid using imported kWh at the price cap (which rose this month to 26.11p kWh), with a saving of £134.90 compared to the standard tariff and £188.97 compared to house consumption costs on a standard tariff. Our exported excess power reached 459.50 kWh (up from 443.10 kWh in June), providing us with Exported Savings of £55.14 this month. This resulted in a monthly bill of -£3.11 including exports, proving that even when the weather is intense, our system remains incredibly efficient.
Grid Usage by Rate
Electricity Usage By Kind
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
Octo-Aid Tariff Comparison
| 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 |
| 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 |
| Metric | Date | kWh |
|---|---|---|
| Best Generation | 3 July 2026 | 31.50 |
| Best front generation | 3 July 2026 | 18.30 |
| Best back generation | 2 July 2026 | 14.60 |
| Worst generation | 23 July 2026 | 17.00 |
| Worst front generation | 14 July 2026 | 8.20 |
| Worst back generation | 30 July 2026 | 5.20 |
| Metric | Date | kWh | Profit |
|---|---|---|---|
| Best kWh export day (Battery) | N/A | N/A | |
| Best Battery and Solar Export Profit | 19 July 2026 | 20.60 | |
| Best kWh export day (Solar) | N/A | N/A | |
| Best export profit | 19 July 2026 | 20.60 | £2.47 |
| Cheapest Day | 6 July 2026 | -£0.64 |
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
Energy Breakdown
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
Intelligent Octopus Go
The costs shown here do include the standing charge. Any comparisons are compared to the unit cost if we were not on IOG. 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.
| Standard Tariff | 24.67p | |
| Standing Charge | 52.19p |
| Cost from the grid | £52.03 IOG | £131.79 Std |
| Savings including export | £134.90 | |
| Monthly bill including export | -£3.11 | |
| Exported (@12p kWh) | 459.50 kWh | £55.14 |
| Charging slots used | 201 | |
| Battery Suspended Slots | 171 | |
| Average unit slot price | 9.74p | |
| Cheapest slot | 8.00p | |
| Most expensive slot | 33.32p |
| House consumed | 753.40 kWh | |
| Car charger | 53.80 kWh | |
| Heat pump | 53.80 kWh | |
| Immersion | 12.80 kWh | |
| Air conditioner | 41.81 kWh |
| Solar generated | 792.50 kWh 2026 | 620.60 kWh 2025 |
| Battery Charged / Discharged | 380.10 kWh | 388.40 kWh |
| Percentage generated by solar | 105.19% | |
| Self-sustained days (solar > consumed) | 17 | |
| Self-sustained days (solar > imported) | 28 |
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.