Solar Panels UK - is it worth it?

[Fly.guy]

So apparently Tesla have opened all Energy product APIs (presumably including Powerwalls) to developers.

Could this finally mean the long-desired integration between IO and Powerwalls??

Should we start emailing Octopus to ask them?

This !

I have 2x PWs, 4.6kW of PV and ASHP heating - all on Octopus Agile Import and Export.

Being able to automatically optimise import to the cheapest 30min slots and then to export when value is greater than the cost of the import (plus a few pence to complensate for charging losses) would be fantastic.

Maybe even an opportunity for an independent app developer to get involved....

 

[notmeguv]

This !

I have 2x PWs, 4.6kW of PV and ASHP heating - all on Octopus Agile Import and Export.

Being able to automatically optimise import to the cheapest 30min slots and then to export when value is greater than the cost of the import (plus a few pence to complensate for charging losses) would be fantastic.

Maybe even an opportunity for an independent app developer to get involved....

Do you know what your average cost per kWh is? I have wondered if Agile or Flux are better than IO+Outgoing(15p) if you have batteries.

 

[ACarneiro]

Do you know what your average cost per kWh is? I have wondered if Agile or Flux are better than IO+Outgoing(15p) if you have batteries.

Depends on how much of your peak load you can shift with your batteries.
I manage pretty much 100% of my peak usage on batteries so IO is a no-brainer.

 

[ringi]

Do you know what your average cost per kWh is? I have wondered if Agile or Flux are better than IO+Outgoing(15p) if you have batteries.

If large battery capacity it needs a lot of PV output to make Flux better then IO. Agile seems to be overpriced compared to night time IO, few nights are cheaper on Agile then IO.

It is even worth people with storage heaters (in large home) buying the cheapeat EV so they can run the heaters on IO!

 

[Fly.guy]

Do you know what your average cost per kWh is? I have wondered if Agile or Flux are better than IO+Outgoing(15p) if you have batteries.

With two PowerWalls we can store almost a whole 'daytime' consumption (mostly the ASHP heating at this time of year) as long as the outside temps are higher than 7-8oC. If it gets colder then that we end up importing a little over the middle of the day. Other than that all 'peak' consumption is covered by the PWs and any PV production. The batteries recharge from 01:00 every night (pulling 10kW) and the car is set depending on when is cheapest pulling another 7kW. The car doesn't do a lot of miles and we let its range drift down on 'expensive' electricity days and then fill up to 90% overnight on windy days or weekends when the cost of electricity is low / negative.

Looking at the most recent bills our average import costs were:

Sep-Oct 2023: 9.72p / KWh (460kWh)
Oct-Nov 2023: 13.16p / kWh (863kWh)
Nov-Dec 2023: 14.66p / kWh (1260kWh)

I dont yet know what the current billing period will cost - but given that it covers the Christmas break when electricity prices were consistently negative for many days I suspect that'll be (on average) under 8-9p / kWh.

 

[Avendit]

With two PowerWalls we can store almost a whole 'daytime' consumption (mostly the ASHP heating at this time of year) as long as the outside temps are higher than 7-8oC. If it gets colder then that we end up importing a little over the middle of the day. Other than that all 'peak' consumption is covered by the PWs and any PV production. The batteries recharge from 01:00 every night (pulling 10kW) and the car is set depending on when is cheapest pulling another 7kW. The car doesn't do a lot of miles and we let its range drift down on 'expensive' electricity days and then fill up to 90% overnight on windy days or weekends when the cost of electricity is low / negative.

Looking at the most recent bills our average import costs were:

Sep-Oct 2023: 9.72p / KWh (460kWh)
Oct-Nov 2023: 13.16p / kWh (863kWh)
Nov-Dec 2023: 14.66p / kWh (1260kWh)

I dont yet know what the current billing period will cost - but given that it covers the Christmas break when electricity prices were consistently negative for many days I suspect that'll be (on average) under 8-9p / kWh.

How do you manage all this? Daily manual fiddling? Set and forget (and hope)? Home assistant? Looking at Dec agile looks really tempting, but I'm worried about the amount of time I'd spend fiddling, and less generous months.

 

[ringi]

With two PowerWalls we can store almost a whole 'daytime' consumption (mostly the ASHP heating at this time of year) as long as the outside temps are higher than 7-8oC. If it gets colder then that we end up importing a little over the middle of the day. Other than that all 'peak' consumption is covered by the PWs and any PV production. The batteries recharge from 01:00 every night (pulling 10kW) and the car is set depending on when is cheapest pulling another 7kW. The car doesn't do a lot of miles and we let its range drift down on 'expensive' electricity days and then fill up to 90% overnight on windy days or weekends when the cost of electricity is low / negative.

Looking at the most recent bills our average import costs were:

Sep-Oct 2023: 9.72p / KWh (460kWh)
Oct-Nov 2023: 13.16p / kWh (863kWh)
Nov-Dec 2023: 14.66p / kWh (1260kWh)

I dont yet know what the current billing period will cost - but given that it covers the Christmas break when electricity prices were consistently negative for many days I suspect that'll be (on average) under 8-9p / kWh.

That's not meaningfully cheaper then doing same on IO but have higher risk and more hassle.

 

[notmeguv]

Depends on how much of your peak load you can shift with your batteries.
I manage pretty much 100% of my peak usage on batteries so IO is a no-brainer.

Apart from Christmas day, which was an outlier, and a couple of very small points where cooking (oven, hob and microwave) exceeded 5kWh momentarily, my Powerwall has covered nearly 100% of peak usage so far. So I guess I’m better sticking with IO.

 

[Fly.guy]

How do you manage all this? Daily manual fiddling? Set and forget (and hope)? Home assistant? Looking at Dec agile looks really tempting, but I'm worried about the amount of time I'd spend fiddling, and less generous months.

I've only had the second battery since September so not sure how it'll shake out longer term. But at the moment I have a fiddle most evenings after the Agile pricing comes out for the next day. Currently the PWs are set to 'Time Based Control' with the 'off peak' time set to run between 01:00 to 06:00

This is based on the long term average unit price for Agile over the last 365 days available here:

Octopus Agile Yorkshire | Energy Stats UK

View historical tariff data for Octopus Agile Yorkshire back to 2018. Claim £50 of free credit when joining Octopus Energy.

energy-stats.uk

Basically the PWs start charging at 10kW at 01:00 and run till about 03:40. I set the car on an ad hoc basis via the schedule function in the app base don current state of charge and what the longer term weather forecast looks like in terms of wind. Which seems to be the primary driver of negative pricing.

So yes, its a bit of a faff and its not perfect. But its OK for now for me as I have an interest.

In the medium term I need to see how the calculations are altered by the possibility for exporting both PV and PW energy (which is still to be set up on my PW controls). This will start to be more of a viable option in the spring once PV picks up and the HSHP doesn't demand everything available. I suspect I can run negative electricity bills over the summer by optimising export. But that remains to be seen.

In the long term I would love to set up automation that can charge the car, manage the PWs and draw on Agile import and export data to optimise everything. Maybe also taking into account forecast sunshine for the day ahead. Although realistically this might be a 'once I'm retired and have too much time on my hands' project...

 

[Pete UK]

I

That's not meaningfully cheaper then doing same on IO but have higher risk and more hassle.

I think this is a very close call. Particularly if you have an ASHP.

If you have enough to last the whole day on batteries in the winter then IOG would appear to be much better on the face of things, with the 15p export. And 7.5p import. Because your average import price is always going to be 7.5p.

If you can’t last all day in winter on battery then Agile could be more beneficial, because you can “top up” during the day at cheaper than peak (which you’d definitely have to pay for at 31p on IOG when your battery runs out). Of course it all depends on the current agile pricing, how much you use, how big/clever your batteries are, how windy it is and so it’s pure guess work.

I no longer have any serious capacity left to discharge in the evenings and I even had to buy a few kW of peak priced electricity (only generated 1.7kW) for the first time last night from about 22:30 due to the colder outside temperature. This is what I had been expecting during my initial planning calculations but when it happened it shattered my revised optimistic hope of surviving 100% on off-peak in the winter

I even put off adding a couple of radiators in the kitchen but it seems that below freezing and the electric floors get really hungry.

2 months of colder weather left to assess.

 

[ringi]

Does Agile tend to cost more on cold days when heatpump uses more electricity?

 

[Avendit]

I even put off adding a couple of radiators in the kitchen but it seems that below freezing and the electric floors get really hungry.

Need to find some way to leverage the HP for the kitchen!

 

[Avendit]

Does Agile tend to cost more on cold days when heatpump uses more electricity?

With the HP obviously you use more power on a cold day to keep the house at a constant temp, but it's not linked to the agile pricing.

I think someone said a few posts up that agile is more closely linked to wind than temp, although when it's really cold it tends to be less windy in the UK.

 

[yessuz]

With the HP obviously you use more power on a cold day to keep the house at a constant temp, but it's not linked to the agile pricing.

I think someone said a few posts up that agile is more closely linked to wind than temp, although when it's really cold it tends to be less windy in the UK.

what is power consumption during the colder days?

meaning peak or daily?

 

[Fly.guy]

With the HP obviously you use more power on a cold day to keep the house at a constant temp, but it's not linked to the agile pricing.

I think someone said a few posts up that agile is more closely linked to wind than temp, although when it's really cold it tends to be less windy in the UK.

Basically, if there is a storm coming through then it's very likely that Agile prices will go negative that night. All the more so at weekends / bank holidays when overall demand is lower.

On sunny days prices also dip around noon (although rarely to negative). So if its cold and sunny then thats the time to top up the PWs to cover the early evening peak rate.

When its dull and cold and not windy then it gets a bit pricier....

In the spring when the sun is stronger and PV is making more of a contribution the mid day top up can come from the PV.

 

[notmeguv]

My export tariff is now live so I entered the export pricing (15p) in the Tesla app. When it first started exporting it showed the solar all being exported and the house load being supplied by the battery, as expected.

After a while though the Solar has been powering the house as well as exporting. Occasionally the solar would also add to the battery as well.

I have tried both the “Solar” and “Everything” settings but get the same result. Is this just because it’s early days and it’s still learning?

 

[Js1977]

You need to set it higher than your import...just put it down at £3 or even 50p assuming you set your import to 30p

 

[notmeguv]

You need to set it higher than your import...just put it down at £3 or even 50p assuming you set your import to 30p

Just tried that, with the export setting on “Everything” and it started dumping the battery to the grid at full pelt. I’ve changed it back as I was worried it would not leave enough battery to get us to 23:30 this evening.

This was with the import price set to 31p and export price 50p.

Should I only be using the “Everything” setting just before 23:30 to get rid of excess battery?

 

[Js1977]

yes just keep it to solar only until the next savings session

 

[notmeguv]

yes just keep it to solar only until the next savings session

Great, thank you