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Christmas Day is a always a great 'worst case scenario' test, to see if your battery storage is sized correctly. Not only was an oven used to bake breakfast (croissants and pain au chocolat), both ovens were then used to cook our Christmas lunch, followed by the main oven being used to cook for guests in the evening. As if that was not enough, our solar panels generated just 1.3kWh during the day. Our central heating was on all day and we have many other appliances in use, including a second drinks fridge.

Our 13.5kWh Tesla Powerwall was never going to power our home for the whole day and I never expected it too. Whilst maintaining a 10% reserve for emergencies, it ran our home up to about 6:30pm, leaving our home running using grid power until the Intelligent Octopus Go tariff cheap rate period starts at 11:30pm.

If our battery storage had lasted all day under this kind of duress, then it would mean we have over-sized it and spend money of storage that is very rarely being utilised. Our current battery manages to power our home on cheap rate electricity for over 95% of the time and it just doesn't make financial sense to install battery storage that will do this 100% of the time.

We hit 15MWh of solar generation today in 769 days from when our solar panels were installed (on the 18^th October 2022). That is an average of 19.5kWh per day.

This month has been terrible for solar energy generation so far. This is the worst start to a month I've seen so far.

This is my rebuilt Home Control System version 7 (HCS7), based around the RPi 4. This is the live machine that runs my smart home software. It sits behind my 12V DC Uninterruptible Power Supply (UPS).

I bought a case with a cooling fan but, it didn't say that the fan lit up and changed colour! The fan helps keep the CPU about 20°C cooler when running on a 5V supply but, I found this too noisy for my liking so I used a 3.3V fan supply. This still ensures it runs about 10°C cooler. It is typically reporting a CPU temperature of around 55°C and this is one of the objects my Home Control System logs and provides a notification if it crosses my set threshold.

This is my rebuilt Home Control System version 8 (HCS8), based around the RPi 5. This is development and test server for my smart home software. The fan uses PWM control and is very quiet. The RPi 5 is noticeably faster than previous iterations and it feels as quick as my laptop in use. Compiling code is very quick too. I'm running the latest OS called Bookworm on both HCS8 and my HCS7.

These 22mm diameter, illuminated, momentary switches are being used in our smart home extension bathroom and master ensuite. They are connected to a slave processor that is part of my Home Control System and pressing them turns on the electric element in the combined radiator and heated towel rail for a set duration. They are illuminated whilst the towel rail is on. These basically enable the towel rails to be used in the summer months, when the central heating system is off.

These use low voltage (12V dc) wiring, so they are allowed to be fitted in a bathroom and I will fit them directly into the wall near the towel rails, as this is much more subtle than a standard switch plate. The switches are also IP rated and vandal proof.

My Raspberry Pi 5 and case arrived. I also bought the official power supply as I need another one to test with.

Finally got around to installing this Drayton Wiser smart TRV in my study. I'm not sure that these things will really add much benefit over the dumb TRVs fitted to all our radiators but, I wanted to asess one and see how well it performs.

I spent a few hours updating my Java Home Control System code to query and control it intelligently. My HCS monitors its battery level as well and sends me a notification if the batteries need replacing. It is ironic, as I'm slowly removing the last few sensors and devices in my smart home that use batteries. Of the 300+ sensors and devices less than 10 use batteries now.

Whilst doing this, I realised that the Java JSON library I've been using was very old! I've upgraded to the latest version and had to update a few of my HCS Java classes to work with this new library. All done now though and it has made the code simpler too.

Whilst developing the code for the TRV integration, I realised that the RPi 3 I've been using for many years is just a bit too slow now. So I've bought a Raspberry Pi 5 4GB to develop on going forward. The only downside of the RPi 4 and 5 are that they use a small fan to keep cool. This was never required on earlier versions. The fans use adaptive speed control though, so they are mostly quiet.

Whilst installing the new integrated Bosch dishwasher, I realised that it is Wi-Fi connected and smart 😎 I really don't want to remotely control my dishwasher via an app (I have set it to monitor only) but, it can optimise its energy usage based on your tariff. I just use a delayed start when I set it off though.

Getting the old dishwasher out proved to be harder than I first thought. The kitchen fitter we used 14+ years ago was a total muppet. Before the worktop was fitted, he decided to put a screw though the top/rear of the frame into the cabinet!

The only way to get to this screw was by taking the old dishwasher apart from the inside out, with a large hammer and a crowbar.

The SSD in my 12V mini-PC Linux Home Control System failed today, after almost exactly 11 years of use. It didn't take very long to build up a new one and I've opted for the Raspberry Pi 4 this time. I develop my smart home code on an RPi 3 and it has been running for 8+ years now without issue. I'm going to rebuild it soon though as it would be handy to have a bit more processing power. I always use USB pendrives for the logging, to off-load as much activity to cheap, solid-state storage as possible. My code has fail-over to redundant pendrives, as I expect them to fail after about 4 or 5 years hard use.

A long weekend in a rented luxury holiday home with extended family (14 of us). These homes give me ideas but, this one was lacking any smart home technology at all. Lovely locaton in the Cotwolds though.

With the whole family away from home for a few days, it is interesting to see how much energy our empty home uses.

This day will mark exactly two years with solar panels. These are some of the key statistics.

We have generated 14.6MWh of electricity and exported 9,985kWh.

Today was a really good example of how well the Intelligent Octopus Go tariff is working with our Tesla Powerwall. We generated 26.8kWh and 98% of this was exported to the grid, earning 15p/kWh. The other 2% was used in our home. We imported nothing at the 26.72p/kWh day rate.

With a relatively long cheap rate window (23:30 to 05:30), our Powerwall only has to run our home for 18 hours and the 13.5kWh capacity is enough to do this all year round, so long as we are reasonably sensible when using appliances. Typically, we do washing on sunny days and run things like the dishwasher over night.

Things that have a significant impact are our electric ovens, the tumble dryer and my son's gaming PC (700W).

Our powerwall powered our home all day and handled any peak loads. The highest was the kettle at 3kWh but, it can handle loads up to 5kW and the solar panels can supply more (up to about 6kW) if it is sunny.

The powerwall state of charge dropped down to 34% before it started charging again at 23:30. Over the whole day, we imported 14.9kWh at 7p/kWH (costing £1.04) and exported 26.1kWh at 15p/kWh (earning £3.92), a net profit of £2.88.

The first charging session for my CUPRA Born didn't go quite to plan last night but, it was mostly my fault. I had not realised that the Octopus App was asking me how much charge % I wanted to add and thought I was setting a target end %, so I set it to 80% and woke up to find the car 100% charged this morning 😊

The charge also started about 10 minutes before 23:30 and so it started to discharge my Tesla Powerwall and then over ran the 05:30 time by about 1 minute and did the same. I need to find a way to stop the EV charging from the Tesla Powerwall. I can do this via the Tesla app by setting the reserve level higher but, that's not going to work when I don't control the charging time.

I made the move to the Intelligent Octopus Go tariff. This gives me 6 hours of cheap rate (7p/kWh) to charge my Tesla Powerwall and my CUPRA Born using my Zappi smart EV charger. This means we can now add more than 35% to our EV battery in one charging session.

In terms of import, we now have no peak rate (it was 35.3p/kWh on Flux) but, we never used peak rate electricity anyway. The day rate is now 26.7p/kWh (it was 25.2p/kWh on Flux) but, the longer cheap rate period should now mean we don't use any electricity in this period either. The Tesla Powerwall and solar energy should see us through the day and the most we should ever pay for electricity is 7p/kWh.

One of the main advantages of the Octopus Flux tariff was the peak export rate (27.0p/kWh) but, in practice less than 20% of our exports fell into this period at the best time of the year. Last month it was just 9.7%, giving an average export rate of 16.3p/kWh). The Intelligent Octopus Go tariff has a flat export rate of 15p/kWh, which is better than the new Octopus Flux tariff export day rate (13.4p/kWh). All this means that we should export even more solar energy and also get paid more for it 😎

The biggest saving comes from our EV charging all being at 7p/kWh. This is much less than Flux (15.1p/kWh). It now makes no sense at all to use the Zappi smart EV charger to charge our EV using solar energy. This will have an even bigger impact when we get our second EV and the MX-5e project is completed.

Having done some calculations, I think I would save at least £500 a year by moving to the Intelligent Octopus Go tariff.

Electricity import rates have increased by about 10% and the standing charge has increased too.

The export rates have dropped and there is more of a financial incentive to use solar energy to charge our CUPRA Born. The exception to this is the export rate at peak rate, which has risen to 27.045p. This encourages export from our Tesla Powerwall.

We generated 690kWh but, it hasn't really felt like it this last week. We've had a lot of rain!

Spent much of the day doing smart blind stuff as we are looking to put them in our new smart home extension and also in many of our existing rooms. I'm trying to better understand the technologies involved and work out how we get a great user experience that works for all the family.

I am evaluating and reviewing the Shelley Dimmer 2 as part of my research into the technologies going into our smart home extension.

This module is designed to sit in the back box, behind a light switch and it supports my preferred MK Grid Plus K4900.

As part of our smart home extension project, I've been looking at the best smart lighting technology to use. My original plan was to use the Fibaro Dimmer 2 modules with MK K4900 momentary (on-off-on) switches. It would appear that our Vera Plus Z-Wave hub is no longer properly supported though, so I'm reluctant to invest in this technology any further. That said, it has worked well for us for many years.

These dimmers are not perfect though, especially when used with a Vera Plus hub. It doesn't report any changes of brightness, on the on/off state changes. Z-Wave generally is the slowest part of my smart home. Every other part of it is very low latency.

I've bought a Shelly Dimmer 2 to test and review. It basically works the same way but uses Wi-Fi for the comms. Hopefully, it will be a lot more open to control and reporting of state.

We reached 13MWh / 13,000kWh of solar energy generation today, 661 days since our installation was completed on 18^th October 2022. That is an average of 19.7kWh per day.

I remain impressed with our Zappi smart EV charger. I had to get the CUPRA Born charged up to 100% quickly for a trip to London and the Zappi allows me to do this using free solar energy. Charging at the Octopus Flux tariff day rate would be much more expensive.

MyEnergi also emailed me today and have automatically opted me in to their Demand Side Response (DSR) programme. I prefer to retain full control of my system and how it behaves, so I have opted back out via their web portal. There is no way my energy provider can know what my plans are and since I am mostly an exporter of solar energy, it isn't going to be particularly useful to me.

July was a good month for solar energy generation with 881.7kWh. This is better than July 2023 (841kWh).

Today was the best generation day of July with 43.8kWh.

We had a new electric roller shutter garage door installed today. I have a project ...

Today we reached 12MWh / 12,000kWh of solar energy generated in 627 days, an average of 19.1kWh per day. Our smart home solar installation project has returned £6,537 on our investment in that time.

A very good month with 961.1kWh generated. In June 2023 we saw over 1008kWh though.

Octopus Energy have informed me that the Octopus Flux tariff prices are changing again from the 1^st July. These are the current prices that came into effect in April. The standing charges are unchanged at 47.849p per day.

On the import side, the peak rate changes are irrelevant to us as as our Tesla Powerwall ensures we never use peak rate electricity. The day rate and Flux rate have both dropped, so our electricity import costs will drop by about £50 per year.

On the export side, the Flux rate changes are also irrelevant to us as we don't ever export at this time of night. The day rate is unchanged but the peak rate has dropped, so we get paid slightly less for the electricity we export. In May about 15% of the electricity we exported was at peak rate, so mostly we look set to gain from these changes.

A great week to end the month on. The second best weekly generation we have ever seen at 259.5kWh.

Perfectly clear skies today resulted in our best generation figure this year, 44.6kWh.

A good generation day, with 43.2kWh generated. One of the best for a while now.

We topped up the electric vehicle, did five loads of washing today and still managed to export 31.5kWh.

The Tesla Powerwall is charging over night on cheap rate energy, to maximise our exports on the Octopus Flux tariff. It uses solar energy to maintain a 100% charge through the day and avoid any import during high load periods.

Exciting news! We have started a smart home extension project.

We have now reached 11 MWh (11,000 kWh) solar energy generated in the 594 days since our solar panels were installed on 18^th October 2022. That's an average of 18.5kWh per day

Our exports in May have been impressive, especially considering we have mostly been using spare solar energy to also power our CUPRA Born. This screenshot is from the Octo-Aid app.

Following the April changes to the Octopus Flux tariff, I currently get paid 15.51p per kWh during the day (05:00 to 16:00 & 19:00 to 02:00), which is very close to the 15.15p that I pay for our cheap 'Flux' rate electricity at night. This means that there is a neglible financial benefit in charging my CUPRA Born over night and I might as well use my Zappi smart EV charger to put the excess solar energy generated during the day into my EV. So I am now doing this as much as possible.

Using 100% solar energy for my transport is easily achievable, given that we typically generate >900kWh in May. The main advantages of this are free charging and being 100% sure that renewable energy is being used for our transport. It means I import less energy from Octopus Energy and I also export less too. The biggest impact will be on the average cost per mile to use my EV, which is currrently at 4.0p per mile. Since we bought it, we have spent £913 on charging to do 22,537 miles.

There are other tariff options, which will allow you to run an EV cheaper in isolation but, within the whole scope of our smart home solar installation project, the amount of solar energy we means Octopus Flux tariff works best for us financially.

What a way for our smart home solar installation project to hit 10,000kWh / 10MWh of solar generation! 🌞

It has taken 559 days to reach 10MWh of generation since our smart home solar installation project went live on the 18^th October 2022. This is an average of 17.9kWh per day.

The Enlight app for our Enphase microinverters matches the generation meter very closely.

In Time-Based Control mode, the Tesla Powerwall does a fantastic job of ensuring we only use cheap rate electricity. It can power both our oven and the the grill simultaneously during peak periods and carry on exporting solar energy at the peak rate on the Octopus Flux tariff.

And this is what the import and export graph looks like. This one shows the Tesla Powerwall and our CUPRA Born charging between 2am and 5am. We then use almost nothing from the grid all day and all evening. The Powerwall may choose to top up the battery with a bit of solar energy during the day, if it is sunny and we have used more than normal. At this timne of year though, the 13.5kWh usable storage is easily enough to do this, with the state of charge rarely dropping below 60%.

Early April and our bills from Octopus Energy are already negative 😎 This includes our gas powered hot water and central heating, standing charges and EV charging. Admittedly £50 of this was from referring a friend to Octopus but, our bills we be negative until November now.

Best generation day of the year so far with 39.5kWh.

We exported 32.8kWh, enough to fill up our MX-5e if it had been completed using our Zappi smart EV charger 😎

March was sunny with 514kWh generated and over 350kWh exported.

Octopus Energy have announced lower electricity rates from 1^st April for both import and export. The biggest change is the large increase in the standing charge though! At 47.849p per day, this comes to £174.65 per year.

The new export rates on my Octopus Flux tariff.

Another new generation high for 2024 at 33.5kWh.

With our new 500Mbps FTTP Internet connection installed, I thought I would check how well the Wi-Fi works inside our home and out in the garden. I'm still using these "old" BT Whole Home Wi-Fi discs that I bought back in 2017. They support WiFi 5 (802.11ac) and 2×2 MIMO. With all of them using Cat5e backhaul (Gigabit Ethernet), I'm seeing Internet download speeds of 460+Mbps (70Mbps up) in every room in our home and the garden, when using my iPhone 13 Pro Max 😎 The BT Whole Home Wi-Fi discs have been amazingly reliable in all that time and I don't see any need to upgrade them any time soon.

Our best generation day so far in 2024, with 28.5kWh. If the cloud hadn't arrived mid-afternoon, we would have exceeded 35kWh and I'm expecting to later this week, based on my Solcast forecast.

I upgraded our broadband connection to FTTP this month. The 80/20Mbps connection we have been using for many years is perfectly quick enough but, when I was notified of the latest price increase, it was £7 per month cheaper to move to a 500/100Mbps FTTP connection and I get unlimited mobile data as an added bonus.

My speed tests revealed some interesting results, not least the one pictured here from my iPhone 13 Pro Max on Wi-Fi. I didn't think these kinds of speeds were possible over Wi-Fi, especially as I'm using quite old BT Home Hub Wi-Fi discs with wired Ethernet backhaul. They support Wifi 5 / 802.11ac though and the iPhone has 2x2 MIMO support. This has got me wondering if the other two discs have 100Mbps or 1000Mbps Ethernet connections.

I have also now been checking the various cables installed in ducting in my home. Some are 15+ years old and use Cat5 Ethernet cable. It looks like some of them support Gigabit Ethernet still though, as the main cable from my lounge to my loft is Cat5 but is connecting a 24-port Gigabit switch at a 1000Mbps.

I've been using the Octo Aid app and it provides some useful data and graphs. This one confirms my thinking that we have started exporting during the peak period in the last few days. We have exported over 140kWh in February already 😎

Best generation day of 2024 so far with 27kWh. Our Solcast forecast was over 35kWh at the start of the day but, cloud moved in during the afternoon.

Today is the first day of 2024 where we have properly exported during the Octopus Flux tariff peak rate (29.9p per kWh between 4pm and 7pm). We have exported tiny amounts before now but, today it started to become significant. The days are getting longer already as the sun reaches higher into the sky. The solar zenith was 62° at 11:30am today, meaning the sun reached 28° above the horizon.

Having looked at our gas usage and costs over winter, I have switched to the Octopus Tracker (December 2023 v1) tariff for our gas. The gastracker.uk website shows the prices have been consistently lower than the 7.3p/kWh we have been paying.

This month has been a good month for solar generation, despite being cold and having plenty of storms across the UK. We have generated over 331.6kWh, compared to 308kWh in January 2023. This is an average of 10.6kWh per day.

With this January being such a good month for generation, I thought I would look back to see how it compares. This is the monthly generation data for my system since it was installed in October 2022.

My yearly average is 7471kWh, my monthly average is 623kWh and my daily average generation is 20.5kWh.

Someone asked last month if fitting solar panels to your roof lowers your loft temperatures. My contextual smart home has approximately 400 sensors and devices including several temperature sensors in my loft, so I thought I would look through the data and find an answer.

• Before solar, the maximum temperature observed was 42.8°C in 2021 and 43.6°C in 2022.
• My smart home solar installation project was installed in October 2022 and the highest temperature observed in 2023 was 33.8°C.

So I would say it does make quite a big difference if the coverage of your south facing roof is as significant as mine is. This "double skin" approach was used on Land Rovers in the desert, to reduce the temperature inside the vehicle.

The 16V PSU that powers the 12V UPS for all my contextual smart home failed today. The first thing I knew about it was that I got a notification telling me the UPS battery level had reached 40%, so it must have failed quite a long time before that. Because the mains power hadn't actually failed, I didn't get notified about that.

This PSU was installed in September 2017 as a new unit to replace another ageing one that dated back to the 1990's. Whilst I wait for a new one to be delivered, I'm running the system directly off a regulated 12V PSU and hoping that we don't have any power cuts, though our Tesla Powerwall will protect it to a certain extent. The large deep-discharge lead acid battery that it uses is currently on a smart battery charger to get it back up to 100%.

I'm having great fun programming some ESP32 processors for our MX-5e's Driver Control Unit (DCU).

I've been using these cheap processors in our contextual smart home to track BLE tags and provide much more timely presence tracking, in parallel with all the other techniques I use.

Our best generation day so far this year at 26.2kWh.

This iPhone screen capture has been compressed vertically.

In this cold weather, we have been really pleased how well our central heating system has worked. We had a new gas boiler installed in April 2022 and this is controlled by a Drayton Wider smart thermostat, which is intelligently controlled by our contextual smart home based upon occupancy and presence.

Since installing the new boiler and completing our smart home solar installation project, our gas usage has dropped by around 30-35% per month. The Wiser thermostat does a very good job at maintaining the set point temperature as you can see from this 'heat report'. The house cools downs quicker than I would like but, it is not super insulated. I have more to do in this respect. The set point changes to 15°C at 10pm on a weekday night (10:30pm at the weekend) and the house temperature drops to about 15°C by 5:30am. At about 6am the set point is 21.5°C again and it reaches this by 9am but, is comfortable long before this time. In March, the heating profile is changed and the heating is barely used at all. Through April to October we turn the space heating off completely and it is only exercised once a week.

This month has been cold but sunny. We have already generated nearly 220kWh and exported 133kWh, earning us over >£18 on the Octopus Flux tariff tariff. That's a daily average of 11.6kWh.

Today was also our best daily generation so far in 2024 with nearly 25kWh. The days are already getting longer and the sun is reaching higher into the sky. Today the solar zenith peaked at 72° (18° above the horizon) at 11:48.

Despite running the washing machine and tumble dryer twice, we exported 60% of the energy generated.

I've not seen this kind of perfect solar generation curve for a long time! Today we generated 23.1kWh and exported 19.5kWh. Our 40° roof helps a lot at this time of year. My smart home logs show that the solar azimuth peaked at 74° at 11:23 today, which is just 16° above the horizon.