Solar Panels UK - is it worth it?

[yessuz]

this thread is a gold mine. I see I need to read whole 60 pages and then to order my solar pannels with battery (PW or not that's a question).

guys, can you, for the stupid one, in very brief explanation, give the difference of PW vs other battries? is just a capacity/discharge rate, or anything else?

 

[WannabeOwner]

having the capability to run without grid draw would be something to consider

I've got a fat a commando socket on the outside of the house that I can hook a nice shiny ICE generator up to ...

... V2H EV would be better though.

 

[spon88]

this thread is a gold mine. I see I need to read whole 60 pages and then to order my solar pannels with battery (PW or not that's a question).

guys, can you, for the stupid one, in very brief explanation, give the difference of PW vs other battries? is just a capacity/discharge rate, or anything else?

I'm in the fortunate position where I can afford a couple of PW if I wanted to. However, I went with a GivEnergy system on the basis that it gives me what I need for considerably less. The battery tech is arguably safer I'm advised (I'm installing 2 units indoors) and the facility to interact with the control system is a lot more "open". The availabilty of PW is also dismal - and that's the gen 2, not the rumoured gen 3.

The downside is indeed the discharge capacity but having plotted our usage, we only draw over 3.6kw for very short periods - e.g. the kids electric shower. Scheduling the other appliances is simple enough to stick with the 3.6kw draw.

Another disadvantage of the system I've chosen is the ramp up time - this is a bit worse than PW but not enough for me to worry about. I also can't do full "failover" in the event of a powercut but I am installing an emergency circuit which I can manually switch to in the event of a power outage. Around us that's very rare but it's nice to have the EPS should we need it to keep the freezers, routers etc running. We have UPS on critical IT gear/CCTV so don't really need immediate fail-over facilities.

So it depends how far you want to go really. My chosen gear should give me 18kwh of usable power for less than the price of one PW and with the vast majority of the functionality. I love my car but it didn't make any sense to me to go with PW given our requirements. If PW 3 is a revelation, I'll look again in a few years time, but I doubt I'll need it unless we start installing air source heat pumps etc.

All of that said, good luck with getting anything installed quickly. I ordered a 10 kwp PV array, inverter, 2 batteries etc around 3 weeks ago and I'm looking at September (earliest) for installation. Just in time for winter!

 

[WannabeOwner]

difference of PW vs other battries

My 2p-worth (no experience of anything other than PW)

We have UPS on critical IT gear/CCTV

My individual-PC type UPSs seem to fail more frequently than we have actual powercuts That doesn't apply to more decent kit - we don't have any problem with the UPS which protects the server room at work (knock-on-wood). So I'm happy to have PowerWall Gateway ... it isn't guaranteed to switch over in time in all instances (forgotten what its weakpoint is - brownout that then leads to a powercut (albeit only for a second or so) - something along those lines).

But even my nearly-knackered UPSs will provide me with a second or two of power, and the capacitors in PCs etc. may well survive a very short powercut ... but even going round fixing all the electric clocks in the house is an inconvenience. Oven won't come on at all until "a time" is set, so its time is never right 'coz no one could be bothered to reset it probably after a powercut when all they wanted was "Turn on darn infernal machine", and after that no one can remember the secret combination of buttons presses to enable resetting it. Poxy UI design.

I work from home and Accountant has put some portion of PowerWall and PV through as business expense (no recollection, might have been anything from 0%-100% for all I can remember)

I am installing an emergency circuit which I can manually switch to in the event of a power outage

Had the whole house rewired a few years ago. Wish they had suggested to me that I might organise "critical circuits" ...

... even with a PowerWall when we get a powercut its either a couple of seconds, or a JCB has gone through a cable and its going to be "some hours". Or its a scheduled powercut probably 9AM - 4PM or maybe lights have gone out during a big storm and probably going to be off for "plenty of hours"

In all bar the "couple of seconds" powercut I would be happy to turn off the non-essential circuits, to maximise PowerWall run time. On the couple of occasions when that has happened I've had to do that manually guessing which circuits we can do without, and that I won't be accidentally turning off a PC with untold hours of unsaved work on it! or the sewage digester thingie

But having the PowerWall run the whole house means that I have "options" in that regard.

(checking APP : 7 powercuts this year, 18 last year ... all "a few seconds" except for one 5 hours and one 8 hours (scheduled for trimming-trees, and one of the big winter storms)

 

[PITA]

I'm in the fortunate position where I can afford a couple of PW if I wanted to. However, I went with a GivEnergy system on the basis that it gives me what I need for considerably less. The battery tech is arguably safer I'm advised (I'm installing 2 units indoors) and the facility to interact with the control system is a lot more "open". The availabilty of PW is also dismal - and that's the gen 2, not the rumoured gen 3.

The downside is indeed the discharge capacity but having plotted our usage, we only draw over 3.6kw for very short periods - e.g. the kids electric shower. Scheduling the other appliances is simple enough to stick with the 3.6kw draw.

Another disadvantage of the system I've chosen is the ramp up time - this is a bit worse than PW but not enough for me to worry about. I also can't do full "failover" in the event of a powercut but I am installing an emergency circuit which I can manually switch to in the event of a power outage. Around us that's very rare but it's nice to have the EPS should we need it to keep the freezers, routers etc running. We have UPS on critical IT gear/CCTV so don't really need immediate fail-over facilities.

So it depends how far you want to go really. My chosen gear should give me 18kwh of usable power for less than the price of one PW and with the vast majority of the functionality. I love my car but it didn't make any sense to me to go with PW given our requirements. If PW 3 is a revelation, I'll look again in a few years time, but I doubt I'll need it unless we start installing air source heat pumps etc.

All of that said, good luck with getting anything installed quickly. I ordered a 10 kwp PV array, inverter, 2 batteries etc around 3 weeks ago and I'm looking at September (earliest) for installation. Just in time for winter!

Has anybody done a hybrid system?

Like Two Powerwalls and a Gateway 2 unit... but then also 18kWh of GivEnergy battery storage?

Mix them together, to extend battery storage capacity?

Like the GivEnergy storage feeds off the Grid during Winter... and then feeds the Powerwalls as they run down... wouldn't matter then about the GivEnergy lower discharge capability would it.

So their only job is to keep the Powerwalls topped up. Let the Powerwalls run the house & Solar distribution at full 10kW - 15kW

 

[Avendit]

this thread is a gold mine. I see I need to read whole 60 pages and then to order my solar pannels with battery (PW or not that's a question).

guys, can you, for the stupid one, in very brief explanation, give the difference of PW vs other battries? is just a capacity/discharge rate, or anything else?

I think, capacity, charge & discharge rate, warranted life and charge cycles and price. Specific chemistry or physical formats depending on your needs? Usability and apps in there, but probably once basic needs are met you wouldn't choose to pay massively extra for a slicker app? Not sure.

£/kWh should be king really, but availability and what the installer with PV availability is offering may trump this.

We have a 10kw puredrive unit coming as that's what our installers are offering and it doesn't go below what I think minimum reqs are on any of the above. Wouldn't be my first choice in a completely free choice (not sure what would be tbh), but it's not a big problem either. Entirely adequate, which is fine.

 

[WannabeOwner]

If you have multiple powerwalls do they charge in parallel?

Otherwise it would seem that x3 won't get done within E7 window, let alone 4-hour Octopus.

I suspect that must be the case, but I'm currently using "Self powered" in order to only charge overnight if I increase the Reserve ... and that is not getting from 10% to 100% in the 7 hours of E7. I think I am remembering that wasn't the case, in Winter, when I was using "Time Based Control" (and Off Peak set to 00:00 - 07:00) so my guess is that they will charge in parallel in that mode

 

[PITA]

If you have multiple powerwalls do they charge in parallel?

Otherwise it would seem that x3 won't get done within E7 window, let alone 4-hour Octopus.

I suspect that must be the case, but I'm currently using "Self powered" in order to only charge overnight if I increase the Reserve ... and that is not getting from 10% to 100% in the 7 hours of E7. I think I am remembering that wasn't the case, in Winter, when I was using "Time Based Control" (and Off Peak set to 00:00 - 07:00) so my guess is that they will charge in parallel in that mode

Yes they do, but it depends on your DNO cable limitations.

If you had 3 x Powerwalls (40.5 kWh storage) but limited by DNO to charge at 3.5kW... then over 4 hours you'll only get 14kWh topup at cheap rate.

If DNO let's you charge at 5kW... then over 4 hours you'll get 20kWh topup at cheap rate.

We've got 2 Powerwalls (27kWh storage) and DNO Approval to charge at 10kW. But the Powerwall battery management system throttles the charging speed to 6.7kW. Because 6.7kW over 4 hours is 27kWh.

If I had 3 Powerwalls (40.5kWh storage), or 2 Powerwalls with a shorter window to charge like only 3 hours, then they would charge at 10kW... perfect. As per my maximum allowance by DNO Approval.

 

[PITA]

One of the reasons I fitted 3 Phase power, and another 3 Phase Ev Charger, was to speed up my capability to charge at high capacity over multiple battery devices... Powerwalls & Ev's.

As an example, I can charge one car at 11kW... another car at 7kW... and two (or three) Powerwalls at 10kW... and run the house in the background... all at the same time.

 

[RagingWhisky]

One of the reasons I fitted 3 Phase power, and another 3 Phase Ev Charger, was to speed up my capability to charge at high capacity over multiple battery devices... Powerwalls & Ev's.

As an example, I can charge one car at 11kW... another car at 7kW... and two (or three) Powerwalls at 10kW... and run the house in the background... all at the same time.

3 Phase will be for the 'next' house

Was quite interesting with regards to DNO single-phase export limits (6kWh on this end) - I hadn't appreciated that once you and your immediate neighbours on the same DNO links in the street get solar, it starts to cap to the export limits of everyone else around you (makes sense i suppose in terms of load coming onto the cabling).

Means that in dense areas+area with many solar panel users, caps will be tighter/stricter.

In all honesty though, export is only reason something to concern if you've favourable tariffs....unfortunate that those have fallen out of favour (Octopus has at least something though).

 

[Avendit]

3 Phase will be for the 'next' house

Was quite interesting with regards to DNO single-phase export limits (6kWh on this end) - I hadn't appreciated that once you and your immediate neighbours on the same DNO links in the street get solar, it starts to cap to the export limits of everyone else around you (makes sense i suppose in terms of load coming onto the cabling).

As long as they are sensible about capping export rather than generation, that isn't too bad I guess? But do they do that?

 

[RagingWhisky]

As long as they are sensible about capping export rather than generation, that isn't too bad I guess? But do they do that?

Generation limited only on the inverter setup you have - DNO side care about those inverters, in as much as they can verify (eyes-on depending on what you're doing) the ability to isolate and 'set' export limits.

Understandable, as I can imagine in the even of works going on in your local distribution area, no-one wants to get electrocuted by the house down the street generation a couple thousand watts going to export!

G99 and G100 certification was a doddle (wasn't expecting as much after reading horror stories), but panels and storage 'go nuts' - for inverters, do research and get advice from experts if not to make sure you maximise what you're going for (I definitely needed the advice, as its a minefield of information).

 

[WannabeOwner]

One of the reasons I fitted 3 Phase power

Is that then a complication with PowerWall / Circuits - having circuits split over phases and PowerWalls on only one phase?

I don't know if you can just put "the whole house, and PowerWall, on one phase" without upsetting supplier because of unbalanced load ... and then presumably stick Charger(s) on a different phase so they never come from PowerWall ... but then how to divert excess Solar to Charger ...

Perhaps could put all the circuits that are never-wanted during powercut on Phase-2/3 ... although personally I'm only going to turn those off during a prolonged powercut and leave them on for the "one second sub-station flip" that we get quite often.

in the event of works going on in your local distribution area, no-one wants to get electrocuted by the house down the street generation a couple thousand watts going to export!

Won't the House be isolated from the grid during that work? i.e. reason why PV won't generate unless is has mains supply - i.e. won't generate during a powercut (unless equivalent of a PowerWall Gateway is installed)

 

[Avendit]

Question for those of you with panels facing multiple directions - is your inverter sized for a simple #panels * power, or is it sized for the expected output accounting for the non-optimal placement of panels? Our quote has taken the first of these routes, so we are getting a 22*375w = 8kw inverter, but I think our max generation is around 4kw. Is this OK, or is it vastly oversizing our inverter and therefore being really inefficient and I should re-challenge on this?

 

[Yachtsman]

Question for those of you with panels facing multiple directions - is your inverter sized for a simple #panels * power, or is it sized for the expected output accounting for the non-optimal placement of panels? Our quote has taken the first of these routes, so we are getting a 22*375w = 8kw inverter, but I think our max generation is around 4kw. Is this OK, or is it vastly oversizing our inverter and therefore being really inefficient and I should re-challenge on this?

I can’t comment on your question except my system is over 3 roofs SW 2.4kW, NE 1.2kW, SE 1.2kW, total 4.8kWp with a 5kW inverter.
Not sure if that helps.

 

[Avendit]

I can’t comment on your question except my system is over 3 roofs SW 2.4kW, NE 1.2kW, SE 1.2kW, total 4.8kWp with a 5kW inverter.
Not sure if that helps.

Useful datapoint, thanks - that sounds like a vote for the second method (sizing to expected output, not installed capacity)

 

[Yachtsman]

Useful datapoint, thanks - that sounds like a vote for the second method (sizing to expected output, not installed capacity)

12 panels is my max due to velux windows.

 

[RagingWhisky]

Question for those of you with panels facing multiple directions - is your inverter sized for a simple #panels * power, or is it sized for the expected output accounting for the non-optimal placement of panels? Our quote has taken the first of these routes, so we are getting a 22*375w = 8kw inverter, but I think our max generation is around 4kw. Is this OK, or is it vastly oversizing our inverter and therefore being really inefficient and I should re-challenge on this?

24panel - east/west direct split with a 6kw inverter. Only clips on extremely sunny days, but even then works for my needs (51kWh lucky generation today).

Higher capacity inverters are great - just need to take into account that some may need more sun to 'kickstart' the generation vs some lower kWh rated models - only really a concern for lower sun times of year (not that we get loads if sun normally anyhow).

If it's potentially a concern on the split, could have 2x lower rated inverters that kick off earlier, but cap at 4-6kw etc.

All down to your individual circumstances for panels, direction and what you're needing to power/store I suppose.

 

[PITA]

Ours is split East & West.

18 x 400W panels.... 7.2 kWp but with a 5kW inverter.

So far, I've not seen it 'clip' much at over 5kW... so I think it's perfectly sized for our array and location.

The SolarEdge HDwave inverter that we have can allow up to 150% of the array size. So 7.2kWp with a 5kW inverter is perfect.

That's as good as we'll get now without being very creative on wall mounts or ground level Arrays.

 

[Avendit]

Ours is split East & West.

18 x 400W panels.... 7.2 kWp but with a 5kW inverter.

So far, I've not seen it 'clip' much at over 5kW... so I think it's perfectly sized for our array and location.

The SolarEdge HDwave inverter that we have can allow up to 150% of the array size. So 7.2kWp with a 5kW inverter is perfect.

That's as good as we'll get now without being very creative on wall mounts or ground level Arrays.

Looking through some spec sheets, the 5kw and 8kw have the same startup voltage, so it could be that the 5g inverters don't suffer from the startup problems the older generations had. Also, I notice that the 5kw is rated as a Max PV power installed as 7kw at standard op conditions, so my 8kw would indeed go beyond this.

So the 8Kw is probably right without messing around with 2 inverters etc.