Hybrid inverter or AC coupled on Solar/Home Battery system

Turnipfarmer

Hey everybody

I'm just about to get a solar array system and home battery system installed at my property.

I've had lots of quotes but some have hybrid inverter (givenergy, growatt) and others have ac coupled inverters including Solaredge.

I'm trying to decide if I should go AC coupled or hybrid for solar generation and battery storage.

Would anyone be able to share their advice and experience? That would be very much appreciated.

QrizB

It's horses for courses, really.

Hybrid inverters are:

• cheaper, because you've only got one box of electronics not two;
• more efficient, because you're converting DC-to-AC-and-back fewer times;
• compatible with generation-limited inverters where you have a big array but no DNO permission.

AC-coupled batteries are more versatile but lack all those advantages. AC-coupled batteries are popular with people who already have solar PV systems that they don't want to mees around with, eg. where they are receiving FITs, which is why you'll see may people on this forum discussing them. For a new installation where FITs aren't available it's likely that a hybrid inverter will be a better option.

Reed_Richards has a hybrid inverter and is a frequent poster; he may have some thoughts to share.

Turnipfarmer

QrizB said:

It's horses for courses, really.

Hybrid inverters are:

• cheaper, because you've only got one box of electronics not two;
• more efficient, because you're converting DC-to-AC-and-back fewer times;
• compatible with generation-limited inverters where you have a big array but no DNO permission.

AC-coupled batteries are more versatile but lack all those advantages. AC-coupled batteries are popular with people who already have solar PV systems that they don't want to mees around with, eg. where they are receiving FITs, which is why you'll see may people on this forum discussing them. For a new installation where FITs aren't available it's likely that a hybrid inverter will be a better option.

Reed_Richards has a hybrid inverter and is a frequent poster; he may have some thoughts to share.

Many thanks for the tips. I'm just trying to work out which is the right way to go on a fresh new installation, I have been leaning towards a hybrid, to be honest they've come in bit cheaper too.

The givenergy system looks pretty good as does the growatt. Anyone here got either givenergy or growatt?

@Reed_Richards thoughts on his hybrid inverter.

We use approx 3500kwh per year but plan to get ev car in future hence researching this. Other decision I've got to make is to go Solaredge or not. We have south facing roof with no shading so doesn't make sense to get it but their monitoring system looks awesome and detailed which is something I quote like look of.

I've had quite a few quotes and it's interesting to see the wide range of size of solar array companies give, ranging from 3.84kw to 5.74. I feel inclined to go with largest array I can fit in there with largest battery I can afford.

Reed_Richards

I am blessed with a loft that has plenty of headroom in the centre and a ladder built-in to the trapdoor for easy access.  So siting the battery in the loft next to the inverter was an obvious solution and meant that I could use a hybrid inverter.  I have not found any issues with this arrangement in the 2+ years it has been in place.  On the plus side my panels are capable of 4.8 kW max so I can sometimes make use of all of that with power over the DNO limit being used to charge the battery.  Typically it might be 3 kW to the immersion heater, 400 W to the rest of the house and the excess charging the battery.  The only potential problem I can think of is that you cannot monitor the output from your solar panels by fitting a clamp-on monitor to the AC output from the inverter because that output could be from the panels or the battery or both.     

Turnipfarmer

Reed_Richards said:

I am blessed with a loft that has plenty of headroom in the centre and a ladder built-in to the trapdoor for easy access.  So siting the battery in the loft next to the inverter was an obvious solution and meant that I could use a hybrid inverter.  I have not found any issues with this arrangement in the 2+ years it has been in place.  On the plus side my panels are capable of 4.8 kW max so I can sometimes make use of all of that with power over the DNO limit being used to charge the battery.  Typically it might be 3 kW to the immersion heater, 400 W to the rest of the house and the excess charging the battery.  The only potential problem I can think of is that you cannot monitor the output from your solar panels by fitting a clamp-on monitor to the AC output from the inverter because that output could be from the panels or the battery or both.     

Cheers, what brand hybrid inverter do you use? Do you find the limitation of monitoring output like you mentioned a problem/deal breaker? I suppose only way around this is ac coupled? Presumably though would the givenergy cloud app be able to see it separately?

Also did you go Solaredge?

Reed_Richards

My inverter is one made by Goodwe, it came as part of the package.  It comes with good monitoring and logging software which I can view both at home or remotely.  I can also view and download data for any day since I got the software running.  For example I can see that 31st July 2020 was a really nice sunny day, unlike today.

I considered buying a diverter for my immersion heater but I was not convinced that it would work in my configuration and might cause the battery to be drained.  I did not have an immersion heater until this year and so far I have just used a programmable switch that I control via an app on my phone.      

Solarchaser

My advice would be to avoid a hybrid inverter, especially the growatt, as I created an array based on the growatt hybrid to run in a garage.
It supposedly had export limiting, excellent efficiency etc etc.
In reality, moving to individual inverters and ac coupling is far more efficient than the growatt was.

I can't speak about givenergy, I've had no experience,  but I'd 100% avoid growatt.

Regarding the array, go as big as the roof let's you, and perhaps don't go with a battery system at all, solar does well, but batteries really struggle to wash their face right now.
At 3500kwh you are a low user, so I think you would struggle to make batteries pay you back over 15-20 years to be honest.

Perhaps post your quote details and we can compare what's a decent deal and what's not??

Turnipfarmer

Solarchaser said:

My advice would be to avoid a hybrid inverter, especially the growatt, as I created an array based on the growatt hybrid to run in a garage.
It supposedly had export limiting, excellent efficiency etc etc.
In reality, moving to individual inverters and ac coupling is far more efficient than the growatt was.

I can't speak about givenergy, I've had no experience,  but I'd 100% avoid growatt.

Regarding the array, go as big as the roof let's you, and perhaps don't go with a battery system at all, solar does well, but batteries really struggle to wash their face right now.
At 3500kwh you are a low user, so I think you would struggle to make batteries pay you back over 15-20 years to be honest.

Perhaps post your quote details and we can compare what's a decent deal and what's not??

Did you have loads of issues with the Growatt Hybrid? Only one quote has got this inverter but I am unsure on the size of the inverter as it does not appear to be listed. The Givenergy hybrid does seem to get good reviews but just not sure if going individual inverters will be better in the long run.

Yes will list them now, give me 5 mins :-)

Turnipfarmer

Solarchaser said:

My advice would be to avoid a hybrid inverter, especially the growatt, as I created an array based on the growatt hybrid to run in a garage.
It supposedly had export limiting, excellent efficiency etc etc.
In reality, moving to individual inverters and ac coupling is far more efficient than the growatt was.

I can't speak about givenergy, I've had no experience,  but I'd 100% avoid growatt.

Regarding the array, go as big as the roof let's you, and perhaps don't go with a battery system at all, solar does well, but batteries really struggle to wash their face right now.
At 3500kwh you are a low user, so I think you would struggle to make batteries pay you back over 15-20 years to be honest.

Perhaps post your quote details and we can compare what's a decent deal and what's not??

This is my shortlist of quotes

1. 5.74kW Array - Growatt Hybrid + Growatt 6.5Kwh Battery = £9025 installed
2. 4.69kW Array - GivEnergy 3.6kw Hybrid + Givenergy 8.2Kwh Battery = £8100 installed
3. 4.69Kw Array - Solis Inverter + Givenergy 8.2Kwh Battery = £8750 installed
4. 4.69Kw Array - Solaredge + Givenergy AC Coupled + Givenergy 8.2Kwh Battery = £9100 installed
5. 4.56kw Array - 5Kw Solaredge Inverter (not sure if Hybrid or not) + Givenergy 8.2Kwh Battery = £8500 installed

Be interested to see your thoughts on these and thanks for your help btw.

Solarchaser

Yeah I had some bother with my growatt, connection issues,app issues, solar issues, but most of all battery issues.

None of your quotes are too out there, roughly 1kw per £1k and in terms of batteries 2kwh per £1k which all seems pretty reasonable. 

If your roof has shading, id say solaredge would be a great benefit, but if it doesn't have shading, I dont really see the point. 

Of all your quotes, the solis inverter has the best reputation, but that is possibly because GivEnergy is still quite a new guy on the scene.

Looking at you more personally if you use 3500kwh a year that's roughly 1200 between April and October and 2300 between October and April,  based on most usage patterns saying when the sun is out you use less electricity. Unfortunately solar works the other way and you get your best 6 months of generation when you need them least.

I'd imagine for ease of application to dno that all the inverters will be restricted to 3.6kw, and probably all provide you with around 4000kwh /year (all rough theorising)

Assuming you use the GivEnergy 8.2kwh battery at 100% dod (datasheet says its a 100% discharge battery) then you could theoretically use 8.2kwh a day with it.

Solar in your best 6 months, let's say is 2700 of the 4000 so over 182 days is 14.8kwh/day.

If we take your brighter 6 months then over 182 days using 1200kwh = 6.6kwh a day, so the battery won't cycle fully, but let's say that the sun gives more than 8.2kwh a day during the brighter months as per the average 14.8kwh and in theory your inverter covers everything in the evening (they usually don't, as tumble dryer and washing machine combined are usually above 3.6kw, not to mention putting on the kettle/oven etc) then in that 6 months assuming a kwh cost of electricity of 15p which appears around average In the UK atm then you would save £180, pretty good right?

Now if we take your duller 6 months you generate about 1300kwh and use 2300kwh, now it's not linear, some bright days you will buy no electric, in the duller days your solar will do almost nothing, but as an average you *could* use all of your solar with the battery so 1300 x 15p = £195

So in theory your combined saving is £375 a year.  Plus you have roughly 1500kwh of solar that you don't use, but can export and get paid for at 5p/kwh so that's another £75 bringing you to a grand total of £450 a year, great right?

However your lowest quote is £8100, so your return on investment is 18 years.

If you get an ev, that will improve roi for solar, but it will make no difference to your battery roi.

If you take the solar on its own, without battery at around £4000 for 4kw with an ev and say a zappi ev charger, your roi will be much better as you will still have a similar savings pattern, but lose much of the cost, though its harder to put that into figures as it very much depends on your indivual usage patterns 

Turnipfarmer

Solarchaser said:

Yeah I had some bother with my growatt, connection issues,app issues, solar issues, but most of all battery issues.

None of your quotes are too out there, roughly 1kw per £1k and in terms of batteries 2kwh per £1k which all seems pretty reasonable. 

If your roof has shading, id say solaredge would be a great benefit, but if it doesn't have shading, I dont really see the point. 

Of all your quotes, the solis inverter has the best reputation, but that is possibly because GivEnergy is still quite a new guy on the scene.

Looking at you more personally if you use 3500kwh a year that's roughly 1200 between April and October and 2300 between October and April,  based on most usage patterns saying when the sun is out you use less electricity. Unfortunately solar works the other way and you get your best 6 months of generation when you need them least.

I'd imagine for ease of application to dno that all the inverters will be restricted to 3.6kw, and probably all provide you with around 4000kwh /year (all rough theorising)

Assuming you use the GivEnergy 8.2kwh battery at 100% dod (datasheet says its a 100% discharge battery) then you could theoretically use 8.2kwh a day with it.

Solar in your best 6 months, let's say is 2700 of the 4000 so over 182 days is 14.8kwh/day.

If we take your brighter 6 months then over 182 days using 1200kwh = 6.6kwh a day, so the battery won't cycle fully, but let's say that the sun gives more than 8.2kwh a day during the brighter months as per the average 14.8kwh and in theory your inverter covers everything in the evening (they usually don't, as tumble dryer and washing machine combined are usually above 3.6kw, not to mention putting on the kettle/oven etc) then in that 6 months assuming a kwh cost of electricity of 15p which appears around average In the UK atm then you would save £180, pretty good right?

Now if we take your duller 6 months you generate about 1300kwh and use 2300kwh, now it's not linear, some bright days you will buy no electric, in the duller days your solar will do almost nothing, but as an average you *could* use all of your solar with the battery so 1300 x 15p = £195

So in theory your combined saving is £375 a year.  Plus you have roughly 1500kwh of solar that you don't use, but can export and get paid for at 5p/kwh so that's another £75 bringing you to a grand total of £450 a year, great right?

However your lowest quote is £8100, so your return on investment is 18 years.

If you get an ev, that will improve roi for solar, but it will make no difference to your battery roi.

If you take the solar on its own, without battery at around £4000 for 4kw with an ev and say a zappi ev charger, your roi will be much better as you will still have a similar savings pattern, but lose much of the cost, though its harder to put that into figures as it very much depends on your indivual usage patterns 

Awesome many thanks for the workings out, very much appreciated. Just been looking at my Agile use and my average unit cost is nearer 18p so will save a bit more on ROI. I do believe our energy usage will go up in few years when my children get older.

I understand the points raised, makes complete sense. Do you think going for smaller battery might be better if not getting full cycle charge at certain times of year on the larger battery or is that bit of false economy?

I'll steer clear of the growatt then by the issues you've described. Out of the rest would you go for the Solis AC coupled setup? It's a little bit more but think the AC coupled setup will be better. Would my monitoring be done through Solis or givenergy if I went this route?

I won't have any issues with shading thankfully and it's a South facing roof so not sure if Solaredge is worth it but I like their monitoring software but is £1k more and won't be anymore efficient in my case and adds onto my ROI.