It's the start of our third winter solar generation season from our 3.69kWp system.
Our Monthly Solar Performance
December 2024
Generation this month was just 73kWh. This was 57% of the expected estimated monthly solar generation of 127kWh. That's the worst December of generation we've ever had, actually that's the worst ever month.
Our self consumption was just 6% of total consumption 533.9kWh. This was low because solar generation is low so we only self used 30.6kWh. We also don't charge our EV from solar generated power as it's still worth more to export it, and secondly because we now charge the home battery overnight at 7p/kWh. This means if there is any solar generation it's generally exported during the day rather than stored in the home battery.
58% of solar generation (73kWh) was exported (43.4kWh) this month. SEG export was actually £6.36 as a total of 43.4kWh was exported.
Our overall consumption was a huge 533.9kWh. This was at a cost of just £37.36 at an average unit rate of 7.6p/kWh.
Rewards from Saving Session has decreased massively this winter. Saving Sessions gave a reward of £0.72
Generation per day over the month of December was very poor. There were only four days over 5kWh. Our highest daily generation was 14th December with 7.7kWh. Our lowest was 0.6kWh, which happened on four occasions.
Our consumption from the grid in December was 503.3kWh.Its obvious in the month's consumption graph that additional mileage in the EV visiting family around christmas increased our consumption.
January 2025
January was an odd month. It was our best start to January ever, but ended in our worst generation in January ever. January's generation was 141kWh, but it was slightly higher than the expected 137 kWh estimated generation.
Our self consumption this month increased to 8% of our overall consumption. We exported 74% (104kWh) of the overall solar generation with a revenue of £15.60. There were three saving session in January. Due to the much lower rates than 2024 they provided an additional revenue of £1.46.
Once again we've not charged the EV from solar because Intelligent Octopus Go lets us charge the EV overnight at a cheaper rate and export at a higher rate.
Generation was very much a mixed bag. It started well, decreased mid month and increased again towards the end of the month. We ended up with 6 days over 10kWh generation which is quite good considering it was January.
Our consumption from the grid (411kWh) in January 2025 was nearly half that of January's 2024's 808.3kWh imported. The main reason was we still have only one EV as my company car is still away at Hyundai and I'm still in a diesel pool car.
Its quite obvious when we charge my wife's EV as our consumption jumps from our normal 5-7kWh home use to 30-40kWh when we've charged the EV.
For the second January in a row we had an issue with our home batteries as the cold weather meant the temperature in our garage dropped to 3.3C. We had to wait two days again for the outside temperature to increase to 7C before I could restart the inverter and home batteries.
We haven't yet separated half the garage off so the batteries would be inside the house. This would stop temperatures dropping too low that they affect the batteries. Due to potentially needing to increase battery capacity if we install a heat pump I have been looking into wether a battery upgrade would be better.
February 2024
The weather wasn't great in February for solar generation. February's generation (159kWh) was slightly better than January's (141kWh), but it was lower than the forecasted 189kWh.
The highest daily generation was 15.8kWh on 27th February. There were 6 days over 10kWh generation. There were 16 days under 5kWh.
Our solar self use consumption was back down to 6% as a percentage of total consumption. We consumed 44.3kWh of solar generation this month, the rest was exported.
Our daily electricity use increased because we were back to two EV's. Hyundai have swapped me into a courtesy EV whilst the Ioniq 5 is still away. Most days we are importing 30-40kWh due to charging one of the EV's. 20th February we imported 72kWh because both EV's were low. We charged one early morning and again early evening, before charging the other on Intelligent Octopus Go overnight. It was more expensive to charge them this way as we were using peak rate electricity as well as low rate electricity. We haven't got used to charging two EV's from one charger yet.
We imported 740kWh from the grid. 125.2kWh charged the home battery whilst the EV's consumed 614.8kWh. Thats a split of 17% home use and 83% EV use.
For another month running we hardly imported any electricity outside of the low cost period. 98% of our imported electricity was at the low rate which is why we averaged 8p per kWh in February.
Generation Performance
Generation performance in December 2024 was very poor. Overall generation (73kWh) was just 57% of the expected estimated generation (127kWh).
Solar generation in January (141kWh) was just slightly over the expected estimated generation (137kWh).
A poor February saw actual generation of 159kWh, which was 84% the expected 189kWh.
For the year so far our actual generation of 373kW is behind the estimated generation of 453kWh. It's not surprising when our solar generation in December and February was lower than expected.
Energy Consumption
Our total imported energy consumption varies greatly each month, although thats mainly due to EV charging. As can be seen in the graph below our home consumption per month doesn't vary too much. We averaged 168kWh per month over winter. Our EV charging is very dependent on mileage but winter does mean lower efficiency, which results in higher electricity import. Its also been different as since start of February we now have two EV's. We've imported 1263.2kWh to charge the EV's. At 2.5 miles per kWh that would be enough for 3158 miles.
Many would likely think that importing 410kWh to 740kWh per month would mean our bill are high. Using smart tariffs and a home battery means we 96% of electricity consumption has been imported using the off peak rate.
We've averaged 10.4p/kWh if including standing charges (and 7.8p/kWh without standing charges).
After export has been credited back to us our monthly winter electricity bill has been £44.38 per month.
Solar, home battery and EV are currently keeping our electricity and petrol bill down to a manageable level.
These costs don't include our heating or hot water as that's still done using gas. Our gas bill for winter has been £222.86 (average of £74.29 per month). Thats a combined electricity and gas bill of £118.67 per month. That covers all of our home use and enough for circa 1000 miles per month too.
Savings
We exported a total of 261.1kWh back to the national grid during the winter months. Self use consumption accounted for 111.9kWh, the majority (110.6kWh) being consumed by the home.
Our savings this winter (£135.51) were 60% of last winter's savings (£228.14). This was partly because we didn't export as much solar back to the grid, but also because we haven't had as much revenue from the saving sessions this winter. This winters saving savings have been paying 13p/kWh compared to up to £2.25/kWh, which means we haven't exported during them.
The savings breakdown is:
* SEG export revenue was £39.17 from the 261.1kWh exported during winter.
* By lowering our average unit rate of imported electricity to circa 8p/kWh by charging the home battery overnight saved a total of £66.15 compared to the standard variable electricity unit rate.
* Self use of solar generation by using solar generation whilst it is generated or by storing it in the home battery saved £27.98.
* Savings sessions and free electricity reward periods provided savings of £2.22.
Summary
Key Statistics for Winter:
* 373kWh generated
* 261kWh exported
* 111.9kWh (6% of overall consumption) self sufficiency from solar
* Solar/Home savings of £135.51
* Diesel saving comparison of £400.69
This will be our third year of having solar and home battery. Now we have two EV's it will be interesting to see how the year progresses compared to last year in regard to performance and savings. We need to get our heads around charging two EV's from one charger, but I'm sure we will adapt to the change.