Inverter single or 3 phase?

[Nickfromwales]

28 minutes ago, joth said:

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.

 

AS we have extended periods of shitty winter weather, it is very much a good strategy to install ( over install ) for some decent revenue when the heating is running, based on an estimated max solar revenue of 25% of the installed kWp of solar panels.

This 12kWp array would be a sub 3kWp array in the winter, a 4kWp less than 1000w.

There is a lot of sense to this approach imho, and even more so if you have an EV which can trickle charge from an EV charger during the day as 'the battery'.

Needs more thought and sense-checking, especially with the forecast of rapidly rising energy costs.

PV and additional batteries for me, but I've decided to sell the battery system I had earmarked, due to an offer I couldn't refuse, and now I will go with an AGM setup instead, due to the much higher bang for the buck, and am awaiting conformation of delivery times for a 24kWh bank. AGM also reasonably unaffected by the Lithium issues of late, other than prices now creeping up in the background.

 

Tesla Powerwalls will not reach new owners doorsteps for well over a year, and they will likely only fill 6 out of 10 orders.

[AliG]

The extra production outside of peak months is a good point. However, the returns on investment are poor for this use. Better to calculate the return over a year.

 

If a 10kW array generated 7000kWh a year and you used it all you would  be getting £2100 a year of electricity (a good chance this falls once the war is over, or we wean ourselves off Russian gas in the longer run). If a 12kW array generated 8400kWh, but all the summer generation was excess, then it might only actually generate 400kWh that is used, so another 5% more return for an almost 20% larger investment. Basically you are cheaper buying electricity in the winter.

 

My 5kW array is more like 100W on many days in winter.

 

Batteries would make a difference but they haven't been considered so far.

 

Nevertheless I think it is difficult without batteries to manage demand to all happen during peak generation during the day.

 

It is especially difficult to make sure the car charges then, after all it is unlikely you drive in the dark and charge during the day.

 

I have not optimised for this amount of PV, but if I look at our use we hardly ever use more.

 

You could have 1kW of background use and 7kW of charging and 2-3kW going into an ASHP. But the reality is that 7kW of charging would charge up a Tesla at a rate of around 20miles an hour. It is unlikely that you run at this rate for more than 2 hours a day.

 

Better to charge at 2-3kW for 6 hours and buy a smaller array. Unless your are regularly driving over 40 miles a day, which is well above average for a privately owned car.

 

You would need to be charging the car, running the ASHP and have the oven on to use 12kW. How often do these all happen at the same time and for a long period of time.

 

[markharro]

On 25/04/2022 at 23:22, Nickfromwales said:

it is very much a good strategy to install ( over install ) for some decent revenue when the heating is running, based on an estimated max solar revenue of 25% of the installed kWp of solar panels.

This 12kWp array would be a sub 3kWp array in the winter, a 4kWp less than 1000w.

Can I check I understand this logic? You are suggesting that over winter a 12kWp array would produce about 25% of peak generation during summer? So that makes 3kWp? What I don't understand is what you mean by 4 less 1000w?

 

To recap, I really need to make a one time decision on the size of the array as it will be integrated with the roof. This is why I am tending towards 11-12kw as its the one chance I have to do this. I will have an EV to soak some of the power up and possibly an ASHP and I work from home so can achieve the max self-use but it seems from what @AliGis saying that this will still force a big export over summer and little payback for this. One of the unknowns it seems to me is what the export price might rise to down the line. Policy changes may force the big power companies to start paying proper £ for to exporters. If that transpires (and we would plan to see out then next 20 years + in the house) then this may make a material impact on the economics. That plus a home battery at some point down the line...

[Thorfun]

8 minutes ago, markharro said:

Can I check I understand this logic? You are suggesting that over winter a 12kWp array would produce about 25% of peak generation during summer? So that makes 3kWp? What I don't understand is what you mean by 4 less 1000w?

 

To recap, I really need to make a one time decision on the size of the array as it will be integrated with the roof. This is why I am tending towards 11-12kw as its the one chance I have to do this. I will have an EV to soak some of the power up and possibly an ASHP and I work from home so can achieve the max self-use but it seems from what @AliGis saying that this will still force a big export over summer and little payback for this. One of the unknowns it seems to me is what the export price might rise to down the line. Policy changes may force the big power companies to start paying proper £ for to exporters. If that transpires (and we would plan to see out then next 20 years + in the house) then this may make a material impact on the economics. That plus a home battery at some point down the line...

I think @Nickfromwales was saying that a 4kWp array would produce less than 1000W (25%).

 

my opinion is you should put as much solar pv as you can afford to now (but also consider what the DNO will allow and what that would mean) and not worry about ROI. no one knows what the future holds and if you've the funds to put in to PV now then just do it. if it's a choice between a 12kWp array or a 4kWp array and much better insulation or, worse case, not being able to afford to finish the project then I think we all know what's the best way to go.

[Nickfromwales]

3 minutes ago, Thorfun said:

I think @Nickfromwales was saying that a 4kWp array would produce less than 1000W (25%).

 

my opinion is you should put as much solar pv as you can afford to now (but also consider what the DNO will allow and what that would mean) and not worry about ROI. no one knows what the future holds and if you've the funds to put in to PV now then just do it. if it's a choice between a 12kWp array or a 4kWp array and much better insulation or, worse case, not being able to afford to finish the project then I think we all know what's the best way to go.

I wanted to both ‘thank’ and ‘like’ your post, but could only choose one lol. Cheers. 
 

 

16 minutes ago, markharro said:

Can I check I understand this logic? You are suggesting that over winter a 12kWp array would produce about 25% of peak generation during summer? So that makes 3kWp? What I don't understand is what you mean by 4 less 1000w?

My apologies. I am

often trying to post in the few sporadic pockets between the chaos of running a business and bring a dad to 4 sprogs. Often I lack total clarity. 
So; 4kWp in the winter will produce 25% of that ( so 1kWp ) OR LESS, during winter, all the way down to zilch. 
I have prospective clients who ask about running central heating during winter by pushing PV output into an ASHP. I ask them what they see when they go outside snd look upwards in December and January. They say “oh, yes, grey clouds” eg zero sun, zero ( excess grade ) solar revenue from the ( fictitious ) man upstairs.

I am stating that you WON’T get as much as 25%  

[Nickfromwales]

My opinion of late, is fcuk the DNO and the indignity of going on bender knee to them to “ask permission” to put a wedge of PV on my ( or your own ) home. They can bite my shiny metal ass afaic.

I am going with hybrid inverters, ( plural ), zero export, non MCS ( as the payments are an insult ), and going nuts with battery storage. 

G100 compliant equipment has been chosen of course, so at the most I need the DNO to come visit to do a “witness visit” to confirm that my equipment does NOT export anything whatsoever. Their choice, not mine.

 

I’m fitting panels everywhere so I can get as close to zero import as is possible. I don’t have to worry about how many kWp I’m fitting, as I do not ( will not ) need permission with everything loaded on the D/C side plus zero export limitation. 
 

Anyone worrying over what the current or future export payment value is / will be has seriously lost track of what they set out to do. Who cares about what the export value is, as you should be reducing that to a minuscule amount or less. 

[Wil]

17 hours ago, Nickfromwales said:

 

I’m fitting panels everywhere so I can get as close to zero import as is possible. I don’t have to worry about how many kWp I’m fitting, as I do not ( will not ) need permission with everything loaded on the D/C side plus zero export limitation. 

The problem with this is, you still need permission. It’s a G99 or G100 application minimum. As long as no one dobs you in, there’s potentially no harm done (if the install is up to scratch). But at that point, why not just apply for the G99 anyway?

 

In the event of a fault or poor configuration, you ‘could’ end up exporting the full amount of your solar and batteries simultaneously. If like me you’re on a piddly little local T/X you could damage it and then be liable to your neighbours as well for the lack of power. The (particularly irritating) DNO rules are trying to prevent issues such as this.

 

Don’t get me wrong, I think your approach is fine if it’s properly and safely configured and I’ll be following a similar approach if I can work out how to self-install more solar on my fairly steep roof!

[ProDave]

33 minutes ago, Wil said:

In the event of a fault or poor configuration, you ‘could’ end up exporting the full amount of your solar and batteries simultaneously. If like me you’re on a piddly little local T/X you could damage it and then be liable to your neighbours as well for the lack of power. The (particularly irritating) DNO rules are trying to prevent issues such as this.

Your piddly little local tx is likely 20KVA or more.

 

I am still waiting for someone to explain to me how such a transformer might be fried by exporting say 8KVA of PV in the opposite direction.

 

I am convinced the DNO's in some cases are just trying to fabricate a situation to get the customer to pay for network upgrades that are needed anyway for other reasons.

[SteamyTea]

4 hours ago, ProDave said:

I am convinced the DNO's in some cases are just trying to fabricate a situation to get the customer to pay for network upgrades that are needed anyway for other reasons.

If the person who is benefitting directly does not pay, then we all pay.

 

I still do not understand why I am, in effect, being forced to have a loan, along with meter rental going up, to pay for people that cannot pay their bills.

[ProDave]

23 hours ago, Nickfromwales said:

My opinion of late, is fcuk the DNO and the indignity of going on bender knee to them to “ask permission” to put a wedge of PV on my ( or your own ) home. They can bite my shiny metal ass afaic.

You are not the only one.

 

I was at a house near us, on the same leg of this supposedly overloaded bit of the network and noted he had a lot of PV on his house and garage roof.  How much have you got?  6kW.  How did you get permission from the DNO and how much did they charge you for network upgrades?    "I keep hearing about this notification thing but nobody notified ours or even discussed it"

 

It was fitted a year ago by an MCS registered company.

 

Oh and his smart meter has never worked so he has not received a penny in smart export payments.

[Nickfromwales]

9 hours ago, SteamyTea said:

If the person who is benefitting directly does not pay, then we all pay.

Yes, that’s the greedy pricks who ‘own’ the energy companies.

They benefit in an utterly grotesque way, and we pay for it. 
 

Won’t be long before they get lifted by the ankles and actually have to re-fertilise the crop.

 

15 hours ago, Wil said:

The problem with this is, you still need permission. It’s a G99 or G100 application minimum. As long as no one dobs you in, there’s potentially no harm done (if the install is up to scratch). But at that point, why not just apply for the G99 anyway?

Yes, you’re absolutely right. So, my 8 panel single hybrid inverter will be installed, G100 zero export permission asked for and gained, I’d like to see them demonstrate how a zero export system couldn’t be grid tied, and then give my PV system a squirt of steroids. Subsequent inverters, I will likely need 3 or 4, will be matching equipment and all set to zero export, and all function in parallel. Those dual input hybrids then have a connection for the batteries, so 48kWh of batteries intended. 24kWh for the get-go, then do 12 months statistical data gathering, and then add prob another 24kWh next year.

Aim is for my meter to stop turning. 
After 2 years, and reliable service, I would seriously consider being disconnected and buy a small silent genny just to charge the batteries in winter. 
My standing charge just fecking DOUBLED, so another £500 a year to rent the SAME meter, the SAME cable, and that’s properly pissed me off.
 

I will now pursue this even if purely for spite. But with gas cooking and heating and DHW via solar / immersion / gas during winter, I am confident that my dependency on an electric grid connection is very, very viable and practical. 
 

If and when an EV becomes mandatory, I would assume a lot of improvements will have been done by then and the industry will have to rethink its policy on the cost of electricity. Maybe it’ll be a better grid to come back to, likelihood is something else I suppose. 

[Dillsue]

On 05/05/2022 at 17:24, ProDave said:

Your piddly little local tx is likely 20KVA or more.

 

I am still waiting for someone to explain to me how such a transformer might be fried by exporting say 8KVA of PV in the opposite direction.

 

First sunny summer day after some of Wil's neighbours have installed G98 systems or bigger systems without permission??

 

Our TX is 5Kva just for our house and is getting replaced at the DNOs expense. When our G99 went in they could easily have told us we needed to pay for the upgrade but they said it was under specced by modern standards so they would upgrade it and lower the supply voltage at no cost to us. Couldnt have been more accomodating.

 

The problem with circumventing the rules is if problems start to happen on a section of the grid where theres unauthorised systems,  the DNO will investigate and the unauthorised systems will get disconnection notices. It maybe that the problems have started because neighbours have legitimately added G98 systems but it will be the unauthorised systems that get the disconnection notices and may have to pay for network upgrades before they can reconnect!!

 

 

Edited May 6, 2022 by Dillsue

[MikeSharp01]

On 06/05/2022 at 08:12, Nickfromwales said:

Aim is for my meter to stop turning. 

You still have one that turns? 

[Nickfromwales]

10 hours ago, MikeSharp01 said:

You still have one that turns? 

I wish. Still satisfying to see the letter on the digital displays reading “ReD” ( reverse direction ) when we fire up customers installs.

Basic digital meter in mine, and I get nagged to death by SSE to upgrade to a smart meter, but not sure why they’re nagging. Makes me suspicious. 

[MikeSharp01]

1 hour ago, Nickfromwales said:

Makes me suspicious

Plenty are, but just because you are paranoid it does not mean they are not out to get you. We have had a smart meter at millstone manor for a year, doesn't work / won't commission, bulb sent a chap from Siemens, he looked at it, said it wasn't commissioned and drove off. We have to send photos of the screen to submit a reading and because we are on a dual tariff and the meter is only reading one tariff we spend inordinate amount of time arguing about how to split the bill. The smart meter on the build works a treat though - looking forward to seeing it going backwards when we get the PV🙄.

Edited May 7, 2022 by MikeSharp01
Typo

[Wil]

On 06/05/2022 at 19:47, Dillsue said:

First sunny summer day after some of Wil's neighbours have installed G98 systems or bigger systems without permission??

 

Our TX is 5Kva just for our house and is getting replaced at the DNOs expense. When our G99 went in they could easily have told us we needed to pay for the upgrade but they said it was under specced by modern standards so they would upgrade it and lower the supply voltage at no cost to us. Couldnt have been more accomodating.

 

The problem with circumventing the rules is if problems start to happen on a section of the grid where theres unauthorised systems,  the DNO will investigate and the unauthorised systems will get disconnection notices. It maybe that the problems have started because neighbours have legitimately added G98 systems but it will be the unauthorised systems that get the disconnection notices and may have to pay for network upgrades before they can reconnect!!

 

 

 

Yep, just this. We’re closest to the ancient 15kVA T/x that feeds us and 3 other properties. They’re all single phase but I’m 3phase. If we all stuck 3.68kWp systems on and I did all 3 phases (which I will) we’d be running very close to the limit. Particularly if I took the above approach and just smashed on with maximising the solar on my roof space, I could probably blow that T/X by myself if I went away for a day or two.

 

That said I could also technically pull almost all of the 15kVA available with 60A fuses on my incomer at 240V and Western Power are utterly disinterested in any more solar or upgrading our T/X unless I pay for it. So surely me zeroing myself out of the equation is a positive!!

[PFG]

Replying to the original @ashthekid post:

 

I had my power supply upgraded to 3-phase for future fast EV charging as part of a whole house renovation, which included installing electric cabling from my loft to basement consumer unit for a future solar installation.

 

I signed up for a 3.2kWh SolarEdge optimised PV system with Green Energy Together as part of a local council scheme, which was finally installed recently (GET is a topic for another thread…).

 

However, my contractor had only run a single-phase 3-core cable, hence GET could only install a single-phase SolarEdge 2.2kW inverter which is connected to the L1 phase of my power supply (running a new 3-phase 5-core cable internally from the loft to the basement consumer unit would have been very disruptive).

 

My house circuits are distributed randomly across all 3 phases, although L1 has some key circuits such as kitchen appliances and boiler. I currently have no 3-phase appliances, although intend to install either a single-phase 7kW or 3-phase 22kW Zappi charger as I have an EV on order.

 

I was previously told that having the PV system on only 1 phase wouldn't balance over the other phases, however as @joth has mentioned 3-phase meters should employ net metering (my meter is a "dumb" Landis Gyr E230 and I am on British Gas's waiting list for a smart meter). My average daily consumption is around 16kWh, so will unlikely I will be exporting much, if at all.

 

Having considered downgrading my 3-phase supply to single-phase (which apparently involves capping 2 of the phases and installing a new single-phase meter), I've decided that it would be simpler to keep the 3-phase supply for future proofing, and perhaps rewire my consumer unit so that more base load circuits (including the future EV charger) are connected to L1 phase.

 

Any thoughts on this would be welcome.