2025

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It was a very damp, gloomy and rather depressing January in terms of weather. We had guests over the New Year but after that it has been an empty house. We keep the heating on but not the hotter.

The new Ember programmer has proved its worth as I can adjust hot water, towel rails and pumped hot water timings via the app. I've been experimenting with putting the underfloor heating on 17 degrees and using the heated towel rails each morning and evening to keep the house around 20 degrees. As the MVHR extracts warm air from the bathrooms and then uses that to rewarm the incoming air, I thought it would work reasonably well which it did.

The basic numbers were as follows: For electricity, generation 332 kWh, of which 281 kWh were exported. We pulled in 101 kWh from the grid, used 9 kWh for car charging and for gas we imported 396 kWh. That gives us a negative balance of 207 kWh. Making the point for ASHP, if we had one installed we would be just positive.

February was a month with both dire cloudy and wonderfully sunny weather. It started off with a fairly mixed week and then two weeks of overcast weather. Some days barely registered any generation. Then in the last week we had glorious sunshine and 50% of the month's generation. 

We had a couple of bookings in the month so the usual spike in hot water usage. The Ember smart programmer worked well as I was able to boost heating and turn hot water on the day before and turn things off after departure. 

The overall numbers are possibly subject to late Octopus gas data. The gas smart meter is pretty useless in sending data. It is outside with a clear view of the sky and the electricity meter is in the house. Yet the gas meter constantly misses data and the electricity one works flawlessly. Both the same make so explain that one. Octopus can't. 

Generation was 430 kWh of which 369 kWh were exported. We pulled in another 108 kWh of grid electricity and used 304 kWh of gas. So a negative balance of 43 kWh. Continuing the gas/ASHP debate, the year to date balance on gas (as we are) is minus 250 kWh, whereas if we had the ASHP we would be positive 170 kWh.

What an absolutely gloriously sunny month. Apparently it was the sunniest March since records began just before the First World War. We generated more than 25% more power this March than last with some days nudging 60kWh - in March for heaven's sake. The graph shows the extent by which March this year exceeded last year. April is looking good so far (as of 13th April). July 2024 total affected by technical issues - not the usual British summer weather :-)

Anyway, the numbers as usual. We generated 1060 kWh. and exported 950kWh of that. We imported a mere 77kWh with no car charging. Gas usage was 388kWh and there was one week of guests staying. We still keep the house at normal temperatures even when its empty.

That gives us a positive lance of 485kWh for the month and it means we have a positive balance for the first quarter of 235kWh which is staggering. If we were on the heat pump, it would probably be nearer a thousand kWh positive balance for the quarter.. Numbers shown on table in Summary of Performance page.

I could just repeat the comments from March regarding the sunshine. It was another sunniest month since records began and for us, the sunniest month and most electricity generated since our records began. That however is a distinctly shorter period - November 2023!

We had 22 days of occupancy this month which was good. Some EV charging and plenty of hot water.

Looking at the figures we generated 1360 kWh and exported 1172 kWh. There was an import of 152 kWh and electric car charging of 68 kWh. We also used 606 kWh of gas.

This leaves us with a positive balance of 482 kWh for the month and a year to date positive balance of 717 kWh. The Excel sheet is on the summary page as ever.

Whilst it is great to have more PV, it is concerning that we have yet another record sunny month. April's record generation has been eclipsed (if that isn't faintly oxymoronic) by May's PV generation of 1470 kWh. See the Met Office report at https://www.metoffice.gov.uk/about-us/news-and-media/media-centre/weather-and-climate-news/2025/double-record-breaker-spring-2025-is-warmest-and-sunniest-on-uk-record

The work done last summer by the local network operator to adjust the voltages at the substation is really paying off for us. We are not yet seeing any evidence of our PV system cutting out due to local grid voltage exceeding the limits for PV input. Fingers crossed for the summer months.

In terms of occupation, we are now starting to ramp up with 50% occupancy this month. From June to mid September, the house is occupied all the time.. 

The basic numbers as usual are 1470 kWh generated from the system with half the days (16) generating over 50 kWh. The Octopus app says 1149 kWh were exported but there are three days when the is a zero reading, indicating that the smart meter has not spoken to the app. One to cross reference with bills.

In terms of usage, we imported 106 kWh from the Grid and car charging took 96 kWh. Much of that charging was straight from the PV system as guests used the Eco option on the Zappi - thank you!

Hot water and towel rails drew 264 kWh of gas, so we ended up with a net positive energy balance  of 872 kWh for May, adding to the year to date positive balance that now stands at 1589 kWh

With apologies for the delay in updating the performance, but we had a number of other issues unrelated to Reflections. Anyway, we are now able to get back on track.

June was nearer to the long term average for sunshine, still slightly above the trend, so that meant long hours of sunshine. So our energy generation has remained high. To date, no sign of any local grid voltage issues causing the PV to shut off.

The numbers are 1430 kWh generated and Octopus saying 972 kWh exported. We imported 114 kWh of electricity and 470 kWh of gas with no car charging recorded. So our net positive energy balance was 388 kWh for the month bringing the year to date balance to 1977 kWh.

I thought I'd get ahead of the game and get in July's data now.

Yet another good month with this month and August seeing the house occupied almost continuously. So hot water use is going to be higher than usual. However, no-one is using heated towel rails!

The numbers are eerily similar to the last few months with generation of 1420 kWh generated and 1155 kWh exported. 205 kWh of electricity and 689 kWh of gas were imported and there was 160 kWh of car charging.

That gives us a positive energy balance for the month of 421 kWh and year to date of 2398 kWh. 

This is a huge improvement over last year. Most of this , I think, is due to stopping the PV cut outs because of local grid voltage issues.

As an aside, the amount of CO2 saved is quite low because the UK electricity grid has a much lower carbon intensity now than it had even a decade ago. The lifetime generation of our system is 16,100 kWh which saves 3,116.8 kg of CO2. That equates to 194 grammes of CO2 per kWh. Back in 2000 that carbon intensity was over 500 g/kWh. There are a lot of days now when the carbon intensity is below 100 g/kWh and not just in the summer.

A good resource is www.carbonintensity.or.uk which gives masses of information. Highly recommended.

And to put this in context - every hour's flying in a typical passenger jet emits between 100kg and 250kg  of CO2 per person depending on assumptions. Source https://www.carbonindependent.org/22.html

So I've saved the equivalent of between 12 and 30 hours of flying. Blimey - that's not much. Just goes to show how polluting aviation is.