Powerwall 2 update

[MrBadger]

3.6 (per phase I think) kW is the max export you can do and the only requirement is to notifying the DNO after the fact.

The conversation that I had with my DNO last year was that the limit of 16A (nominal approx 3.6kW) per phase for retrospective approval includes all micro generation sources, including solar and battery. So if you have solar and want to install another form of micro generation such as battery storage even if no plans to export from storage you still need to get approval prior to installation. If your one and only install is 16A or less and your new install is 16A or less, then you can go a fast track route, but you still need prior approval from the DNO to show that its compliant and notify them when commissioned. I got the impression that even if there was no intention to export from battery, ie battery storage prevented export, then the DNO would still grant an export limit for the storage - which may have a use if it was then decided to financially benefit from further grid export.

 

[Country Boy]

When I had solar and and a powerwall2 installed, the DNO got their knickers in a right twist.

I had 5kW of Solar, and a 5kW inverter. This was set with a maximum export of 3.68kW.

The DNO made the installer remove the inverter and replace it with one that had a maximum output of 3.68kW. They also insisted the power wall be capped at 3kw, not 5kW in or out.

About 6 months after this was all installed, I did have a fault on the system and the power wall started exporting to the grid, so this did make some sense.

On sunny days like today, my solar output is limited from 11am to 3pm which means less miles in the M3.

 

[Simavon]

Yes. In essence, DNO aren’t concerned by Powerwalls because they don’t export (unless by separate agreement). My limit is 7Kw for my primary panels which were installed in 2015. My secondary panels can’t export. I have a 100amp supply. Internally, I can draw 20Kwh without using the grid, being the total available from panels and batteries.

This is the wording from the DNO after we looked into additional solar, and storage:

"after a network analysis the existing connection cannot take any more solar, and can only take a battery with a capacity of 3.68kW with a G100 limitation to 0kW export."

 

[Dilly]

This is the wording from the DNO after we looked into additional solar, and storage:

"after a network analysis the existing connection cannot take any more solar, and can only take a battery with a capacity of 3.68kW with a G100 limitation to 0kW export."

Ouch! The Government drive for sustainable power is going nowhere with situations like that.
In terms of solar, we were in a similar situation. Our 7Kw array is the Max we could export but we added 3.9Kw which is prevented from exporting. If our use falls below what the 7Kw array is exporting, the 3.9Kw array shuts down and lights up again as the situation changes.

 

[KennethS]

When I had solar and and a powerwall2 installed, the DNO got their knickers in a right twist.

I had 5kW of Solar, and a 5kW inverter. This was set with a maximum export of 3.68kW.

The DNO made the installer remove the inverter and replace it with one that had a maximum output of 3.68kW. They also insisted the power wall be capped at 3kw, not 5kW in or out.

About 6 months after this was all installed, I did have a fault on the system and the power wall started exporting to the grid, so this did make some sense.

On sunny days like today, my solar output is limited from 11am to 3pm which means less miles in the M3.

Seeing that production graph both annoys me (because it demonstrates that the DNOs are curtailing the full potential of Solar PV in this country) and makes me jealous in comparison to my meagre 3.5kW system!

 

[Simavon]

Seeing that production graph both annoys me (because it demonstrates that the DNOs are curtailing the full potential of Solar PV in this country) and makes me jealous in comparison to my meagre 3.5kW system!

We have 9.9kWp split over two 4.0kW inverters, which leads to this:

 

[Fred2]

East/west setup? Did you have to jump through hoops along the lines of “yes that’s 2 x4kW inverters but it will never hit 8kW unless there’s 2 suns” ?

 

[ACarneiro]

This is the wording from the DNO after we looked into additional solar, and storage:

"after a network analysis the existing connection cannot take any more solar, and can only take a battery with a capacity of 3.68kW with a G100 limitation to 0kW export."

This makes no sense. What do they care how much you store in your home if you're not allowed to export anyway? If none of that power ever touches the grid, why do they even have a say in it?

 

[Simavon]

East/west setup? Did you have to jump through hoops along the lines of “yes that’s 2 x4kW inverters but it will never hit 8kW unless there’s 2 suns” ?

Yes - slightly misaligned so the W facing panels do better. We didn't have any issues, apart from needing a reasonably prompt response as we applied in early February 2019 with the FiT going away the following month. The system was commissioned with about 3 weeks to spare. We would have gone ahead with a 3.6kW setup if we had to. The split seems to work well, we'd previously not realised it was a feasible option. On a clear day we get a good spread of output - it climbs rapidly from sunrise compared to a south facing array.

 

[Simavon]

This makes no sense. What do they care how much you store in your home if you're not allowed to export anyway? If none of that power ever touches the grid, why do they even have a say in it?

It's about output rating, not storage capacity. Let's say there is a grid fault and your RCD immediately trips, your panels and power wall are all working maxed out, then in our case we'd be putting in theory up to 15kW onto the local grid (7kW from Powerwall and 8kW solar) until the power wall and/or inverters shut off.

 

[ACarneiro]

It's about output rating, not storage capacity. Let's say there is a grid fault and your RCD immediately trips, your panels and power wall are all working maxed out, then in our case we'd be putting in theory up to 15kW onto the local grid (7kW from Powerwall and 8kW solar) until the power wall and/or inverters shut off.

Isn’t that a certification problem with the Gateway, then? It either is certified to shut off within a specified timeframe or it’s not?
I’m not being deliberately obtuse, I’m just truly mystified by the whole situation…

 

[Dilly]

Isn’t that a certification problem with the Gateway, then? It either is certified to shut off within a specified timeframe or it’s not?
I’m not being deliberately obtuse, I’m just truly mystified by the whole situation…

I believe that PW gateway 2 has a fail safe for such events and breaks with the grid in microseconds. I presume it‘s belt and braces by DNO’s.
or are there phantom power cuts...

 

[Country Boy]

Lots of the issues with DNOs is not to do with the normal situation, but what happens in fault situations. Being able to predict what can happen in fault conditions is notoriously difficult.

One of the issues is Islanding.. In the event of a power cut, my system (gateway 1) is supposed to shut down.. If this is delayed by a second or 2, power can be sent back to the grid... Now if my neighbour on the same phase (all single phase here in the sticks) has solar, that can see my output, and thinks the grid is still up so carries on working and exporting...

Now my system sees the output of my neighbour, thinks the grid is back, and starts exporting again..

Now we have an island which is self powering.

A lines man comes out to fix the fault, and gets zapped by the output of the island.


Yes I know this is far fetched, and there are safety systems present to stop this happening.. but it is possible, and therefore the DNO makes the rules it does.

 

[Mattallica]

Any idea when these will be purchasable in the UK alongside the solar roof tile replacements?

 

[ACarneiro]

Any idea when these will be purchasable in the UK alongside the solar roof tile replacements?

Solar roof is not being mass produced yet. They can barely make enough for the US and, as far as I’m aware, hasn’t been launched internationally.
Powerwall supplies are also severely constrained (the chap who fitted mine says he has 80 on order and they’re just about trickling in every few months).
I ordered 2 more and the order was placed in September. Delivery has been pushed back for the third time now (they now say end of June, but I’m not sure I believe it)

 

[KennethS]

Solar roof is not being mass produced yet. They can barely make enough for the US and, as far as I’m aware, hasn’t been launched internationally.
Powerwall supplies are also severely constrained (the chap who fitted mine says he has 80 on order and they’re just about trickling in every few months).
I ordered 2 more and the order was placed in September. Delivery has been pushed back for the third time now (they now say end of June, but I’m not sure I believe it)

On the recent earnings call Elon said that Powerwalls made since November last year have a higher output capacity, so the wait may actually benefit you if having extra output potential is of any use to you. I always try to look on the bright side, but I know that waiting is never ideal. I've been contemplating adding a second Powerwall to our home but I can't make the numbers work (yet).

 

[Dilly]

On the recent earnings call Elon said that Powerwalls made since November last year have a higher output capacity, so the wait may actually benefit you if having extra output potential is of any use to you. I always try to look on the bright side, but I know that waiting is never ideal. I've been contemplating adding a second Powerwall to our home but I can't make the numbers work (yet).

We added a second one. The numbers never will stack up realistically but the extra charge/discharge rate is really useful as is the extra capacity.