August Solar Generation and Export Numbers
Despite the lingering heat waves that saw us running the Samsung Windfree air conditioning for 10 nights, our saving remained robust. The additional cooling didn't dent generation, it just meant less of it went spare for export. The air conditioning used 30.79 kWh
Solar Generation
We set a new solar generation record this month, beating our previous best by 58.4k kWh. . Our total generation reached 618.80 kWh, which is significantly higher than the 548.10 kWh we produced during the same period last year. However, this was still 173.70 kWh lower than the 792.50 kWh we generated in July. Our best generation day was on the 7th of August, we hit 28.10 kWh, whereas our lowest generation was a poor 6.60 kWh on the 29th. The West/North facing rear panels on the back of the house are beginning to decline as the evenings draw in..
Battery Performance
Our strategy focused on efficiency, utilising 237 charging slots at an average grid slot cost of 8.58p, which was a notable improvement over the 9.74p average we saw in July. We managed to charge 437.10 kWh into the battery while discharging 450.10 kWh to power the home. We are still force exporting between 4pm-7pm. To achieve this, we used more charging slots this month compared to the 201 used in July, this meant less suspensed charging slots being used. This month we used 134 compared to 171 last month.
Grid Usage
House consumption for the month sat at 706.50 kWh, which was 46.90 kWh lower than the 753.40 kWh consumed in July. Despite this lower consumption, our grid import rose to 598.60 kWh compared to 546.48 kWh last month. Our cheapest day occurred on August 8th, where we achieved a -52p result. We remained highly disciplined with our timing, as 92.97% of our usage occurred during off-peak periods, with only 2.31% falling into On Peak and 4.73% on Smart Charge. Regarding exports, we sent 412.10 kWh back to the grid, which was 47.38 kWh lower than the 459.48 kWh exported in July.
Cost Savings Summary
Our monthly bill including export came to £18.85, which was £12.70 higher than the £6.15 we paid in July. When comparing imported kWh to our tariff and the price cap, we achieved savings of £141.74, while comparing house consumption to the same metrics yielded another £164.60 in savings. Our export savings for the month were £50.55, which was £4.59 lower than the £55.14 we saw in July. Currently, our average unit cost for the year stands at 12.32p against an average price cap of 26.16p.
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
| 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 | 7 August 2026 | 28.10 |
| Best front generation (pv2) | 1 August 2026 | 17.50 |
| Best back generation (pv1) | 7 August 2026 | 11.30 |
| Worst generation | 29 August 2026 | 6.60 |
| Worst front generation (pv2) | 27 August 2026 | 3.40 |
| Worst back generation (pv1) | 29 August 2026 | 3.00 |
| Metric | Date | kWh | Profit |
|---|---|---|---|
| Best Battery and Solar Export Profit | 7 August 2026 | 21.10 | |
| Best export profit | 7 August 2026 | £2.53 | |
| Cheapest Day | 8 August 2026 | -52p |
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
One of the best features of my Home Assistant setup is this level of visibility. This chart breaks down our entire home's power profile, from high-draw circuits like the immersion heater and car charger to specific devices like the TV and office UPS systems. It’s a powerful way to monitor our daily habits and see how different parts of the house contribute to our overall energy footprint.
Home Assistant Individual Device Usage and Energy Flow
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 | 26.11p | |
| Standing Charge | 52.19p |
| Cost from the grid | £53.18 IOG | £160.59 Std |
| Savings including export | £141.74 | |
| Monthly bill including export | £18.85 | |
| Exported (@12p kWh) | 412.10 kWh | £50.55 |
| Charging slots used | 237 | |
| Battery Suspended Slots | 134 | |
| Average unit slot price | 8.58 | |
| Cheapest slot | 8.00p | |
| Most expensive slot | 33.32p |
| House consumed | 706.50 kWh | |
| Car charger | 22.67 kWh | |
| Heat pump | 50.33 kWh | |
| Immersion | 8.18 kWh | |
| Air conditioner | 30.79 kWh |
| Solar generated | 618.80 kWh 2026 | 548.10 kWh 2025 |
| Solar vs last year | +70.70 kWh | |
| Battery Charged / Discharged | 437.10 kWh | 450.10 kWh |
| Percentage generated by solar | 87.59% | |
| Self-sustained days (solar > consumed) | 12 | |
| Self-sustained days (solar > imported) | 16 |
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.