Powerwalls in the UK

[Slumberjack]

I wonder if this charge is a new thing because, as I said earlier, it wan't mentioned when we signed up for our solar upgrade and Powerwall in August 2020?

Does anybody have any pre 2021 experience with this?

As we're an all electric house with 8kW of solar, our issue is that when we're heating water it can draw from the grid even when we have sufficient battery. I'm not sure how this will pan out in the long run as we've only had the Powerwall since November, and I would expect in the summer that we'll have ample power and it won't be an issue, but as others have said, it a lot of cost to recover in potential savings. Almost 4000kWh at our current rate.

 

[JohnRatsey]

I agree that it's rational that the PW should be able to supply 5kW for the household without being subject to the 16A limit on export to the grid. It appears that Tesla, for all its infinite skills and wisdom, haven't considered what is the normal operating condition. As we get pushed towards heat pumps then more PWs and maybe more solar may become financially attractive.

 

[xWren]

I wonder if this charge is a new thing because, as I said earlier, it wan't mentioned when we signed up for our solar upgrade and Powerwall in August 2020?

Does anybody have any pre 2021 experience with this?

My discussion with installers took place in May 2020, that is when one of them offered to enable 5kWh without DNO approval because getting that was slow and "expensive" but I didn't get an actual cost. The other installers I got quotes from didn't seem to know much about it, so not surprized it wasn't mentioned to you. I pursued it with one other installer and as a result got letter from the DNO telling us we could have 3.8kW but would need to apply for anything else. It then took until April 2021 nearly a year later before the Powerwall was in stock to buy. I don't think the charge is new, but could vary between DNO, and lack of installer experience/knowledge/interest plays a part.

 

[xWren]

It appears that Tesla, for all its infinite skills and wisdom, haven't considered what is the normal operating condition.

LOL. It is obvious from the poor time-based control algorithm that normal Powerwall use in UK was not considered in the design.

 

[JohnRatsey]

I noticed this morning that I can now set rates in the Tesla app and wait to see if £0.05 for off-peak and £0.25 for peak plus £0.05 for export encourages the battery to be generous in the off-peak charging and not be seduced by the occasional sunny day into thinking that summer has arrived.

 

[JCUK]

We had the update allowing us to set the rates in early December. Putting the correct rates in did not appear to have any effect in forcing it to charge in off-peak; and putting the peak rates at 10 times off-peak still did not have any effect. There does not appear to be any risk factor in its calculations. However when we entered a sell price for peak considerably more than off-peak cost the powerwall charged to 100%. Unfortunately it would then send solar generation to the grid. We now enter a high peak selling price in the evening and change it to zero in the morning. This results in us being able to fully charge the powerwall when we expect the weather to be cloudy.

 

[JohnRatsey]

After I cut back the peak rate to 15p and export rate to 4p the enthusiasm for full charging has disappeared and behaviour is similar to that observed previously. Nonetheless, the facility to change the rates is a big step towards manual control over the charging behaviour when a significant change in the weather is forcast (the worst case being several sunny days followed by thick cloud or snow).

 

[JohnRatsey]

The forecast for today was rain which followed two sunny days. I therefore increased the peak rate to 25p from 15p and the battery fully charged itself during the off-peak period. Historic Powerwall behaviour suggests that if I hadn't made this change then it would have expected today to be also sunny and start the day significantly below 100%. With some sun expected tomorrow I've changed the peak rate back to 15p. The facility to manipulate the rates is a substantial improvement on having no easy user control over the battery. It's a bit like having a stick to steer a donkey in roughly the right direction compared to having no control at all.

 

[xWren]

It's a bit like having a stick to steer a donkey in roughly the right direction compared to having no control at all.

LOL. The uncertainty about what charging behaviour the time based control mode might produce for any entered price is still too much for me. Our solar managed to generate 6kWh one day and 300W the next, Tesla's algorithm just can't cope with that kind of variation. So I continue to drive my donkey using a RPi and setting the power reserve percentage and mode appropriate for off-peak charging, and run in self-powered mode the rest.

Such a shame that Tesla are unwilling to give users the level of control offered by GivEnergy, makes that an attractive alternative for house battery in UK .

 

[Yachtsman]

Hi John, you can still get full utilisation of your PW even if your export is limited to 16A.
I’ve a setup similar to yours 4K plus 1 x PW and my DNO application was refused, but my installer has setup the system so exporting is limited.
When the PW is still accepting charge, all solar can be utilised to charge it and for house use all solar is available for the house use if needed plus 5kW from the PW, but when the PW is full, all solar and 5kW PW is still available for the house but if I start exporting solar this is limited to 3.68kW and if the unused solar being exported exceeds 3.68kW the solar gets clipped. Therefore I get to use the full output of my PV system for internal use and I still get to use the full 5kW of the PW day or night. Only exporting is affected.
So if your setup is really annoying you there are ways around it.

LOL. The uncertainty about what charging behaviour the time based control mode might produce for any entered price is still too much for me. Our solar managed to generate 6kWh one day and 300W the next, Tesla's algorithm just can't cope with that kind of variation. So I continue to drive my donkey using a RPi and setting the power reserve percentage and mode appropriate for off-peak charging, and run in self-powered mode the rest.

Such a shame that Tesla are unwilling to give users the level of control offered by GivEnergy, makes that an attractive alternative for house battery in UK .

Unfortunately the givenergy inverter only accepts two solar strings else it would have been on my shortlist.

 

[JohnRatsey]

LOL. The uncertainty about what charging behaviour the time based control mode might produce for any entered price is still too much for me. Our solar managed to generate 6kWh one day and 300W the next, Tesla's algorithm just can't cope with that kind of variation. So I continue to drive my donkey using a RPi and setting the power reserve percentage and mode appropriate for off-peak charging, and run in self-powered mode the rest.

I don't have the option of using the reserve level to control the off-peak charging as I bought my PW nearly 4 years ago when the backup gateway wasn't available. I haven't written off the possibility of having one fitted in the future should I get a second PW to support heap pumps.

The other frustration is the 16A limit when supplying the domestic demand. I can understand the 16A limit for export but we should be able to have our PWs configured to supply the full 5kW to the house without getting a permit from the DNO. I suspect this is a consequence of regulations not keeping up with technology.

 

[xWren]

The other frustration is the 16A limit when supplying the domestic demand. I can understand the 16A limit for export but we should be able to have our PWs configured to supply the full 5kW to the house without getting a permit from the DNO. I suspect this is a consequence of regulations not keeping up with technology.

I share your frustration. Without the 16A limit I would be able to shift all my grid supply to the off-peak period, instead we try to juggle the use of kitchen appliances! It could be regulation lag, it took long enough for island mode to be permitted in UK at all, or just badly drafted rules from Ofgem. On the other hand can Tesla guarantee that the amount the Powerwall can deliver only goes into the house and never onto the grid even briefly? Perhaps a common limit is the only control they have. Meanwhile the DNO are rewarded for being risk adverse, and can charge £750 for a simple bit of network voltage analysis, but it is down to Ofgem really.

 

[JohnRatsey]

I share your frustration. Without the 16A limit I would be able to shift all my grid supply to the off-peak period, instead we try to juggle the use of kitchen appliances! It could be regulation lag, it took long enough for island mode to be permitted in UK at all, or just badly drafted rules from Ofgem. On the other hand can Tesla guarantee that the amount the Powerwall can deliver only goes into the house and never onto the grid even briefly? Perhaps a common limit is the only control they have.

Load juggling isn't easy. When the kettle needed replacing I got one that was nearer 2kW and not 3kW to reduce the kettle load spikes. The 16A limit, however, becomes less significant if the sun is shining and some/all load is supplied directly by solar generation. The 16A limit will become a bigger issue as we get herded towards heat pumps which will add to the domestic base load for half of the year.

The voltage rise on the local mains created by one battery briefly exporting power is going to be insignificant compared with solar panels on several nearby buildings all exporting at the same time and likely to exceed the demand from other houses in the vicinity. Perhaps we somehow need to lobby Ofgem to allow 5kW or more? Batteries in different houses won't all export at the same time unless planned to do so (eg this Tesla Energy Plan from Octopus Energy ).

 

[NikoV6]

Should just update this! The £750 was what Scottish Power (the DNO) were charging me for submission of the G99 and G100 certificates. I moaned to them that this was unacceptable and after an internal review, have lowered the cost to £250 + VAT. This covers the desktop exercise to check suitability of network wiring to my property. The other £350 + VAT I am being excused is for the witness attendance by them to ensure I am not exporting more than 5kw. They don't need to do this as it's a known Tesla battery install

 

[xWren]

Load juggling isn't easy. When the kettle needed replacing I got one that was nearer 2kW and not 3kW to reduce the kettle load spikes. The 16A limit, however, becomes less significant if the sun is shining and some/all load is supplied directly by solar generation. The 16A limit will become a bigger issue as we get herded towards heat pumps which will add to the domestic base load for half of the year.

The voltage rise on the local mains created by one battery briefly exporting power is going to be insignificant compared with solar panels on several nearby buildings all exporting at the same time and likely to exceed the demand from other houses in the vicinity. Perhaps we somehow need to lobby Ofgem to allow 5kW or more? Batteries in different houses won't all export at the same time unless planned to do so (eg this Tesla Energy Plan from Octopus Energy ).

LOL, I did exactly the same with the kettle to reduce spikes (every little helps). Yes once the sun is out I have way more flexibility. Already have an air source heat pump (no mains gas to the site) that heats our thermal store for supply of DHW and heating. I run it in the off-peak period in winter, and to sometimes reduce our export of solar in autumn/summer (might as well have some more heat in the house than feed the grid) but our solar thermal often circumvents that by already heating the store. It is evening cooking e.g. oven + hob + microwave + lighting etc. that hits 16A limit for me.

Yes I have a new house with recent tech, but it takes smart householders to manage it optimally. Heat pumps do not make direct replacements for gas boilers, it also needs changes to other equipment and life style. I wonder when this reality will become more common knowledge to those caught in the rush away from carbon emissions?

I suspect that Ofgem are very slow to change anything ever, innovation is not their thing nor is listening to the public. Maybe someone calculated just how much the network would have to change to allow capacity for every home to have solar panels and batteries, panicked and slapped a low limit on for "safety". I think local generation has lots of good aspects but the National Grid and DNOs will certainly have to develop new models for planning and balancing the grid to accommodate it and the changes to consumer behaviour.

 

[David_ffg]

Very interesting thread which I’m reading along with several other threads which seem to suggest that running a PW in the U.K. Is quite far from the hands-off experience Tesla seem to be espousing!

I’m about to trigger a solar PV and PW installation, and take delivery of a M3 LR so it’s a new world to me.

2 different PW installers have now recommended the Octopus/Tesla tariff which seems to me to get round all these issues, the PW simply does its thing, any import or export to the grid is at the same rate (currently 12p) so ALL my solar is credited back to me, and I don’t have to juggle peak/off peak rates.

Thoughts?

 

[xWren]

Very interesting thread which I’m reading along with several other threads which seem to suggest that running a PW in the U.K. Is quite far from the hands-off experience Tesla seem to be espousing!

I’m about to trigger a solar PV and PW installation, and take delivery of a M3 LR so it’s a new world to me.

2 different PW installers have now recommended the Octopus/Tesla tariff which seems to me to get round all these issues, the PW simply does its thing, any import or export to the grid is at the same rate (currently 12p) so ALL my solar is credited back to me, and I don’t have to juggle peak/off peak rates.

Thoughts?

A significant point is why you have a battery. If it is just a means of getting a net tariff for PV, and your solar generation makes that worthwhile ROI, then go for it! I always thought that a net payment system, effectively bi-directional metering, was a better way to manage domestic power, so broadly supportive of what Octopus/Tesla tariff offers. I am with Octopus (just not that tariff), have been for several years now and happy with their service and prices.

Not knowing your situation here is some of my reasoning for mine:
One reason for having a Powerwall was continuity of supply. I am rurally located, power outages in bad weather happen and leave me without water too. Having a Powerwall capable of "island mode" also means that I can continue to use our solar generation in a power outage. I would not want Tesla deciding when to export from my Powerwall to balance the grid, or how much to charge it (badly anticipating tomorrow's generation and use), their algorithms are not that smart.

Also as an existing PV installation on reasonable FIT and with our use profile, I can do better on Go tariff and using the currently 5p off-peak rate "intelligently". Controlling our domestic systems manually is already a part of daily life and so the Powerwall is not a burden to manage (if only I can get full control of it). I guess it depends if you are enthusiastic to save every penny, or if you prefer not to have to think about the details.

Hope that helps a little, I'm still going to keep watching the market and tariff offers and see where it goes in the future.

 

[David_ffg]

A significant point is why you have a battery. If it is just a means of getting a net tariff for PV, and your solar generation makes that worthwhile ROI, then go for it! I always thought that a net payment system, effectively bi-directional metering, was a better way to manage domestic power, so broadly supportive of what Octopus/Tesla tariff offers. I am with Octopus (just not that tariff), have been for several years now and happy with their service and prices.

Not knowing your situation here is some of my reasoning for mine:
One reason for having a Powerwall was continuity of supply. I am rurally located, power outages in bad weather happen and leave me without water too. Having a Powerwall capable of "island mode" also means that I can continue to use our solar generation in a power outage. I would not want Tesla deciding when to export from my Powerwall to balance the grid, or how much to charge it (badly anticipating tomorrow's generation and use), their algorithms are not that smart.

Also as an existing PV installation on reasonable FIT and with our use profile, I can do better on Go tariff and using the currently 5p off-peak rate "intelligently". Controlling our domestic systems manually is already a part of daily life and so the Powerwall is not a burden to manage (if only I can get full control of it). I guess it depends if you are enthusiastic to save every penny, or if you prefer not to have to think about the details.

Hope that helps a little, I'm still going to keep watching the market and tariff offers and see where it goes in the future.

Thanks! Helpful ideas.
Of course Octopus Go rate for new customers is currently 31.7/7.5, making it less attractive still. I presume it will go further north of these figures in April.

It’s an attractive thought to be charging my new Tesla M3 completely free (at least in summer) but realistically I will still be exporting to the grid at times in summer for almost no return, and paying heavily in winter. I like the way Tesla Energy Plan pays for all of my solar at the same price I buy it back - no waste. Also less fiddling about!

 

[lincsat]

I've just found this thread from a google search and will add my 2p worth.

I had the PW2 with gateway installed in December. I'm not aware of paying the £750 (or anything) to the DNO, they did give approval and come out to fit a 100A company fuse, (previously 80A). It does discharge at 5KW.

I set the time based control from Day 3 when it first became available, I'm on Go faster (22:30 - 02:30) and the PW has fully charged every night until 2 Days ago, it's now charging to 80-82% with charging finishing at 01:15 - 01:45

With what others have said about the algorithm and costs, I wonder if the answer is to have 3 price zones with the highest rate being the last Hour before cheap rate, then the PW may decide to charge more overnight so as not to incur the highest costs. I've just set my app for these settings and will see what happens

 

[lincsat]

Well nice theory but it didn't work. Sun went behind a cloud and it started drawing from the grid despite charge level of 72%. Guess it was saving for the new peak slot.

I've reverted to the 2 tier rates and set the cost for peak higher to see if that helps.