Jump to content

Inverter single or 3 phase?


ashthekid
 Share

Recommended Posts

10 minutes ago, SteamyTea said:

Makes it worth getting a 3P meter as it offsets then imports at 35p/kWh.

Interesting point, but I think on single phase you wouldn't need the offset as you would simply be able to use all the electricity you generate before you start to import any. The offset I assume is only for instantaneous use.

 

My feeling is that three phase is better if the extra cost is similar as it gives more options in the future for export and more capacity should you ever need it.

Link to comment
Share on other sites

1 hour ago, joth said:

So you could put generation on one phase, all your house hold usage on a different phase, and it would still only charge you for the difference between import and export at any given moment.

Currently in heated debate over this. What is your information source to clarify this functionality, please? Genuine question, not provocation btw! 

Link to comment
Share on other sites

On 14/12/2021 at 23:11, ashthekid said:

I must admit I don't totally understand. I suppose i just assumed it was always best to match the 3 phase with a 3 phase inverter.

 

I am planning on future-proofing the property and having an EV charging point but don't have an electric car to use it yet.

 

The 11 panels and optimisers are already installed. The installer is planning to come back when the rest of the project is finished or at least the 1st fix electrics are in.

I'm in a strict conservation area so 11 was all I could fit on a particular roof within the planning criteria.

 

At some point when battery costs come down i am planning on adding some sort of battery storage onto the setup.

And have plans on installing an air source heat pump for UFH and hot water. Am hoping this PV array go some way to helping with that.

 

Just need to make sure i have the correct inverter though before it's too late.

This is important for me too. 3 phase is what the extricate car needs . My solar panels in a conservation area will need to be integrated  not fixed on tiles .  The idea is to supply all our electricity needs and run mvhr pump and hot water and air source heat pump. 
my fear is the installers just do their fix and are not thinking of the integrated systems . Any ideas on this , without messing the builder ??

Link to comment
Share on other sites

2 hours ago, Dillsue said:

If you want to go down the route of an oversize system with export limitation then youll need to get permission from your DNO with a G99 application. If you propose an export limitation device or the DNO asks for one, then youll also need a G100 application. Both G99 and G100 aplications each have their own costs. On top of design verification fees our DNO wants £375+vat to witness an export limitation system.

 

If you want more than the 3.68kw G98 limit then speak to your DNO as they may well be able to accomodate you generating more. Ours was very approachable and we seem to have informal agreement to have 2 x 3.68kw export. Hopefully get that formalised when they process our G99 application.

 

I can't believe how much hassle this is. I don't have the budget for a specialist to make these applications for me and I doubt I would have a clue how to fill in the forms myself. To summarise, if I want to put a standard system on my roof of up to 3.68 then I still need this G98 permission? I thought there was no admin involved with that at all!? anything above that if I want to export back unpaid (because it wont be MCS installed) I need to make this G99 application? If I want to export limit, then I need a G99 and G100? This is ludicrous for a residential punter. 

 

I simply want to have a >3.68 system to use my whole roof capacity and not waste the generation potential and the DNOs should be forced to accommodate this it really makes me fume. Btw I have already contacted the Scottish Gov and our DNO to complain about the process/fees involved in a supposed age of climate change but to no avail.

Link to comment
Share on other sites

38 minutes ago, markharro said:

 

I simply want to have a >3.68 system to use my whole roof capacity and not waste the generation potential and the DNOs should be forced to accommodate this it really makes me fume. Btw I have already contacted the Scottish Gov and our DNO to complain about the process/fees involved in a supposed age of climate change but to no avail.

There has to be a difference between low power domestic systems and large scale generation. The cut off has been put at 16 amps per phase. Now that could have been 12 amps, or 25 amps, but it is 16, live with it. Or fill in the right form and pay the fees.

It is a bit like taking a car test, you have to meet minimum criteria, but it does not qualify you to drive an articulated 44 tonner. 

  • Like 1
Link to comment
Share on other sites

45 minutes ago, markharro said:

To summarise, if I want to put a standard system on my roof of up to 3.68 then I still need this G98 permission?

Yes, but think of it less like permission and more like registration. You do it after install. The paperwork is a doddle. The DNO need to know where there is generation on the network for safety, maintenance and ops reasons.

Link to comment
Share on other sites

2 hours ago, Nickfromwales said:

Currently in heated debate over this. What is your information source to clarify this functionality, please? Genuine question, not provocation btw! 

 

The Smart Meter SMETSv2 polyphase spec mandates this "net metering"behaviour. I have 

I've linked it many times over the years, but here it is again:

 

https://www.gov.uk/government/consultations/smart-metering-equipment-technical-specifications-second-version

Page 87

"Consumption shall be the sum of the cumulative Active Energy Imported on 
the importing measuring element(s) of its Electricity Meter less the sum of the 
cumulative Active Energy Exported on the exporting measuring element(s) of 
its Electricity Meter;"

 

i.e. you just add up all the import in the given time period and subtract all the export in that time period to calculate total consumption.

 

 

@Dan F also got some supplier(s) to confirm this. (And has empirical evidence?)

 

  • Thanks 1
Link to comment
Share on other sites

1 hour ago, markharro said:

 

I can't believe how much hassle this is. I don't have the budget for a specialist to make these applications for me and I doubt I would have a clue how to fill in the forms myself. To summarise, if I want to put a standard system on my roof of up to 3.68 then I still need this G98 permission?

In my experience its straight forward dealing with the DNO, but you do need to know what it is youre asking them. In previous posts youve mentioned 20kw, 11kw and 3.68kw. Different rules apply depending on what you want to do. 

 

Have you actually looked at any of the forms? They are pretty straight forward.

 

I dont really agree with your frustrations about controlling the public exporting to the grid. If it were a free for all, we'd have melted copper, burnt insulation and smouldering transformers all over the country,  and no electric.

Edited by Dillsue
  • Like 1
Link to comment
Share on other sites

Thanks - I dont disagree that there needs to be control. My point is that the DNOs should be forced by legislation to make the process much easier for residential punters like me and also scrap all fees.

Link to comment
Share on other sites

11 minutes ago, markharro said:

Thanks - I dont disagree that there needs to be control. My point is that the DNOs should be forced by legislation to make the process much easier for residential punters like me and also scrap all fees.

I’m not an electrician and I managed to fill in the G99 application for UKPN. Took me about 30 minutes.

 

Initially I was worried because the doc I received to fill in seemed lengthy but it boiled down to some questions on one side of A4 IIRC.

Link to comment
Share on other sites

5 hours ago, markharro said:

Thanks - I dont disagree that there needs to be control. My point is that the DNOs should be forced by legislation to make the process much easier for residential punters like me and also scrap all fees.

A typical residential punter puts circa 4/5kw on their roof wired to a 3.68kw export limited inverter.  All they have to do is fill in a G98 notification form and send it to their DNO. No fees, no drama, easy peasy. As has been mentioned the G98 notification is straight forward to complete. As its a notification and not an application, so long as youve used a G98 compliant inverter they can't stop you having your PV.  They may ask for clarification if youve made a mistake but that's the worst that is gonna happen  

Link to comment
Share on other sites

9 hours ago, joth said:

 

The Smart Meter SMETSv2 polyphase spec mandates this "net metering"behaviour. I have 

I've linked it many times over the years, but here it is again:

 

https://www.gov.uk/government/consultations/smart-metering-equipment-technical-specifications-second-version

Page 87

"Consumption shall be the sum of the cumulative Active Energy Imported on 
the importing measuring element(s) of its Electricity Meter less the sum of the 
cumulative Active Energy Exported on the exporting measuring element(s) of 
its Electricity Meter;"

 

i.e. you just add up all the import in the given time period and subtract all the export in that time period to calculate total consumption.

 

 

@Dan F also got some supplier(s) to confirm this. (And has empirical evidence?)

 

I’m an Octopus customer in exactly this situation.  I have 3 phase PV, 3 phase smart meter, 1

x Tesla Powerwall and net metering is real, trust me 😬

  • Like 1
  • Thanks 1
Link to comment
Share on other sites

  • 3 weeks later...

Still struggling to get my head around PV plans not made any easier by absolute failure to engage with any installers at the moment - they all seem too busy. This and the clock ticking down to finalising our BW application. I remain keen to fit around 11/12 Kw to maximise our roof space real estate as I am only going to get one chance to do this if using inset GSE trays to fit. That is also a convenient number for a pallet purchase. The problem however is in knowing that I can safely plan to make use of these on single phase (I think I have been convinced out of 3 phase and in any event have no idea how much it would be to get a 3 phase connnection)? Is there an export limited inverter that would deal with this size of array that would satisfy the DNO? And if so, does that mean that I can be guaranteed that I can plan for this size of instal with a G98 going in afterwards to advise the DNO?

 

And on the separate issue of MCS instal or not, perhaps @AliG can comment on this, if not getting an MCS instal does that mean that you can't qualify for the Octopus Tesla package? What are the other implications? Is it only that you wont get paid for any export - if so I cant see this being a problem for me unless there was a serious rise in the price paid for export in the future.

 

Also @AliG could you recommend your installer and if so provide me with their details? thanks

 

Link to comment
Share on other sites

You'll never self use the full capacity of 12kW array, even with a battery, so personally I'd go MCS and G99 and attempt to get payment for anything unused. With a 8kW array we get about £250/yr in exports. A well oriented 12kW array could get double that, depending on self usage.

And that's before any future price rises.

 

There was a listing the other day for a self install system with the option of a  MCS cert for and extra £345.

 

If the G99 is rejected then 3ph or export limitation is plan B and C, but either of those cost more than the G99.

 

 

 

 

 

Edited by joth
Link to comment
Share on other sites

4 minutes ago, joth said:

You'll never self use the full capacity of 12kW array

Even in Edinburgh which is where we are? But my thinking is to future proof. The excess may go to "waste" atm with export limitation but the hope would be for future policy changes which might make it easier/cheaper to get permissions to stick the whole excess output into the grid coupled with enhanced export prices.

 

8 minutes ago, joth said:

There was a listing the other day for a self install system with the option of a  MCS cert for and extra £345.

What do you mean by a "listing"?

 

10 minutes ago, joth said:

If the G99 is rejected then 3ph or export limitation is plan B and C, but either of those cost more than the G99.

I am still struggling to understand this. Lets forget about 3phase for the moment. I understand that you use a G99 if you want to be able to export more than the 3.68 on single phase and that the DNO charge for this application. But the other thing it seems to me is that until you have made this application you dont know if it will allowed and I need to know now what I can instal.

 

So that takes me to the export limitation option. I had understood that with the same example of a 12Kw array but using an export limiting inverter the DNO only got advised after the instal via G98 and then had to accept it assuming the inverter you use is compliant. So why is export limitation more expensive? Does the G98 application carry a higher fee? 

Link to comment
Share on other sites

7 minutes ago, markharro said:

Even in Edinburgh which is where we are?

What does PVGIS say?

https://re.jrc.ec.europa.eu/pvg_tools/en/

 

8 minutes ago, markharro said:

What do you mean by a "listing"?

A link on here to an eBay listing.

 

 

9 minutes ago, markharro said:

the DNO charge for this application

No a lot though? ours was included in the supply& install price so I don't even know what it was, but nothing compared to the £3000 it would have cost us to go 3ph

 

13 minutes ago, markharro said:

ut the other thing it seems to me is that until you have made this application you dont know if it will allowed and I need to know now what I can instal

 

So decide the plan assuming export limitation, but put a G99 for it anyway as it will give you more "future proofing" if it is accepted.

 

14 minutes ago, markharro said:

So why is export limitation more expensive?

 

It may vary by inverter, but with solaredge you have to buy additional hardware to enable export limitation.

Also, it will limit your choices to just those inverters your DNO recognises as being allowed for export limitation.

 

And no I don't believe you can install and notify under a G98 route I think having>3.68kW inverter with export limitation still needs a G99 and permission in advance anyway, but others may know differently.

 

 

Link to comment
Share on other sites

Another scenario is you have 12kW array installed but the  only 10kW is approved in the G99 (let's say).

So you could put all the panels on a 10kW inverter and that would probably be fine, or you could hold a few panels back to make another string to put on a DC battery charger to run DC loads from (I had this as my plan B, as the home automation and most the lighting is 24V)

Link to comment
Share on other sites

Hi Mark,

 

My installer was RB Grant https://www.rbgrant.co.uk

 

They are an electrician which i felt more comfortable with than a fly by night PV installer who popped up to take advantage of short term demand.

 

If you ask SP Networks for a price for three phase they will come back to you within a few days. If you have a three phase cable passing by, which you may well have it will not be expensive.

 

Intelligent Octopus only requires taht you have a Tesla, MCS is required only if you want paid for export which is separate to this.

 

The Tesla Energy Plan which includes a Tesla Powerwall needs an MCS install.However, the savings aren't that great over Intelligent Octopus that they would pay for the Powerwall cost plus there is a massive waiting list for Powerwalls.

 

You would hardly every use 11-12kw of electricity at one time, so if you installed this on a non MCS system part of your capacity would provide absolutely no return.

Link to comment
Share on other sites

You could fit and wire the modules on all your roof. Then connect up what you are allowed to.

Try calling your DNO and explain, some people are helpful. The PV team at WP down here are very good. No nonsense engineers.

Link to comment
Share on other sites

On 24/04/2022 at 09:55, markharro said:

Even in Edinburgh which is where we are?

 

I am still struggling to understand this. Lets forget about 3phase for the moment. I understand that you use a G99 if you want to be able to export more than the 3.68 on single phase and that the DNO charge for this application. But the other thing it seems to me is that until you have made this application you dont know if it will allowed and I need to know now what I can instal.

 

So that takes me to the export limitation option. I had understood that with the same example of a 12Kw array but using an export limiting inverter the DNO only got advised after the instal via G98 and then had to accept it assuming the inverter you use is compliant. So why is export limitation more expensive? Does the G98 application carry a higher fee? 

Outside of peak sunshine months, youll likely to be able to use everything a 12kw array will produce. Year round production is where bigger arrays come into their own.

Youll always have an export limit. If you cap export at the 3.68kw G98 limit then you just notify the DNO. If you want to export more than 3.68kw then you need to apply for chargeable  permission and that permission would come with an export limit determined by what the local grid can handle or what grid upgrades you want to pay for. How you limit the export is up to you but youll need to convince the DNO that you have an effective limitation system in place.  Weve applied for 2 x G98 certified inverters in our G99 application so 2 x 3.68kw. You could have an inverter(s) without a certified limit and add an export limitation system. The export limitation system would need a G100 application in addition to the G99 application. 

Speak to your local DNO and they may be able to give you an informal indication of what you can connect, ours did and was very helpful.

Link to comment
Share on other sites

11 hours ago, Dillsue said:

Outside of peak sunshine months, youll likely to be able to use everything a 12kw array will produce

Depends what you call peak months. 

For the half year March - August, we exported over half generation on an 8kW array, and that's with a full home automation system working to maximize load shifting as far as I can.

I expect with 12kW  it would be an even higher % going unused.

 

Edited by joth
Link to comment
Share on other sites

On 24/04/2022 at 10:31, AliG said:

You would hardly every use 11-12kw of electricity at one time, so if you installed this on a non MCS system part of your capacity would provide absolutely no return.

Unless you had a decent size battery bank?

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

×
×
  • Create New...