New Solar PV installation

SD_DRACULA · 29-03-2021 8:13pm #1

Looking to get a new solar pv system installed before the tariff thing comes in, probably 4kwh and battery and I am looking for suggestions from people on the forums i.e. what companies to look at and which to avoid (can PM me if that's not allowed here for some reason)

A few questions:

- Looking at 12 panels (4kwh total), a 3kw battery, hybrid inverter and got a quote from a company for about 6.5k after grants so not sure if that's a decent price or not.
- Only problem is that the front of the roof might not fit all 12 panels and it is south facing and I rather not put some panels on the back roof since that never sees sunshine.
- I do have a building out back with south facing roof but not sure can put a few panels there and mix with some on the front of the house? Was told it would need a separate inverter as you can have cables from those panels all the way to the attic where the house panels are?
- A 3kwh battery sounds very tiny and not sure is of much benefit (We go through 15-20 kwh every day) is there a point to battery if FIT comes in? Will they credit kwh like for like?
- I do have a hybrid EV which has a 12 kwh battery but seeing that drain about 4000w when charging so not sure the solar pv can keep up with it anyway
- Now everyone is at home/wfh so usage is high enough during day

garo · 30-03-2021 11:05pm

Price is a bit high. You could get the same setup for about 1000 less. A battery that is large enough to cover your usage will be very expensive. A 3kWh battery is enough to qualify you for the additional 1200 SEAI grant. Ask your installer for a with and without battery quote. Without a battery you don't need to get a hybrid inverter and can use a non-hybrid that saves costs. With the FiT the economics works against the battery.

Most inverters these days are dual string i.e. they can accept panel arrays with two orientations. You could possibly have the outhouse array feed the same inverter - but you'll need a way to get the PV cables from the outhouse to the inverter.

slave1 · 30-03-2021 11:38pm

Read the 2020 Quotes thread, there’s lot of useful info there and most your questions answered.

DrPhilG · 31-03-2021 1:22am

garo wrote: »

A 3kWh battery is enough to qualify you for the additional 1200 SEAI grant.

Doesn't have to be 3kw, I got the grant on a 2.4kWh battery.

SD_DRACULA · 31-03-2021 9:43am

garo wrote: »

Most inverters these days are dual string i.e. they can accept panell arrays with two orientations. You could possibly have the outhouse array feed the same inverter - but you'll need a way to get the PV cables from the outhouse to the inverter.

I was told for this I need a second inverter in the shed which would drive up costs considerably as you can't run cables from panels that long (not sure why) would be something like 15-20m from shed to house attic

DrPhilG · 31-03-2021 9:46am

SD_DRACULA wrote: »

I was told for this I need a second inverter in the shed which would drive up costs considerably as you can't run cables from panels that long (not sure why) would be something like 15-20m from shed to house attic

My second string is at the end of a 85m cable and connected to a dual MPPT Solis hybrid inverter.

SD_DRACULA · 31-03-2021 11:30am

DrPhilG wrote: »

My second string is at the end of a 85m cable and connected to a dual MPPT Solis hybrid inverter.

Ok so either that's BS they told me because of extra effort or could it be that you might lose efficiency/power over a long cable?
Also apparently if not all panels are getting same power from the sun (i.e. if one is shaded) it can bring down the power of the rest of them but there must be a way around that, optimizers or a better inverter that can deal with different values from multiple panels?

garo · 31-03-2021 11:55am

All panels on one string should be getting the same sun. If you have two strings the panels on each string can face different directions. I have an E/W install with a single inverter.
Optimizers are only needed if you have shading issues or want to combine panels facing different directions on the same string.

SD_DRACULA · 31-03-2021 12:08pm

Main front roof is south facing but due to weird shape might not be able to get 12 panels but only 10 which won't give me full 4kw.
Was thinking just adding 2 panels on the back of the roof (north side) and I do see sun there but ofc not as much as the front, would it be even worth it?
Shading maybe a little on the front in the morning from the chimney. Would only go over one panel or two max.

slave1 · 31-03-2021 6:08pm

SD_DRACULA wrote: »

Main front roof is south facing but due to weird shape might not be able to get 12 panels but only 10 which won't give me full 4kw.
Was thinking just adding 2 panels on the back of the roof (north side) and I do see sun there but ofc not as much as the front, would it be even worth it?
Shading maybe a little on the front in the morning from the chimney. Would only go over one panel or two max.

Just two panels N facing on a separate string is not worth it.
To give you an indication I have a SW/NE setup and this month about 10% of my generation is from the NE, N would be worse

unkel · 31-03-2021 7:12pm

N still gets 50% of S over the whole year, so with panels as cheap as they are these days, it could still very well be worth it. Agree with the 2 panels on a string though. 3 minimum, preferably 4

SD_DRACULA · 01-04-2021 9:52am

Another company said to do 2kws on south roof and 2kws on the north but I'm not sold on that idea.
It looks like max I can get on south face is 10 panels of 375w which would give me more power than 2kw south and 2kw north.
Anyone using those Puredrive II 5kwh batteries? Heard they're pretty good and if you top them up with a night tariff

mun1 · 01-04-2021 5:10pm

Your inverter might not get enough voltage from 2 panels. On my Solis inverter it needs to be 120V , which is 4 panels.

Never thought N gets 50% of south .
You have me looking at my north facing shed roof .

unkel · 02-04-2021 12:55am

Indeed. You might also try 3 panels on a string on your Solis inverter. You might be surprised at what it does. Hint: it works

SD_DRACULA · 05-04-2021 9:05am

Thinking of a different setup now, 8 panels on main roof and 8 on the shed, 2 strings, both south facing but in the cold months the house can cast a shade over the whole shed roof (been sunny there for over a month now). Is there a point putting optimizers on the 8 panels on the shed since the shade will be during the lowest generation months?

graememk · 05-04-2021 9:56am

SD_DRACULA wrote: »

Thinking of a different setup now, 8 panels on main roof and 8 on the shed, 2 strings, both south facing but in the cold months the house can cast a shade over the whole shed roof (been sunny there for over a month now). Is there a point putting optimizers on the 8 panels on the shed since the shade will be during the lowest generation months?

If they are on a different string you don't have to, but all of them will have to be out of shade before they will generate full power

garo · 05-04-2021 4:53pm

Don't think it is worth it if there is shadow in winter only. I have one string that has some panels shaded from Nov-Feb but I calculated and the optimizers would never pay for themselves. I miss out on maybe 90kWh a year.

slave1 · 05-04-2021 5:01pm

Agreed, my NE facing string frozen over weeks on end over Winter, sun never hits them directly

garo · 05-04-2021 5:27pm

The only reason why I would go for optimizers in your case is that the panels are south facing. That *may* mean you get more out of them than my due E and slave1's NE panels. You'll have to do the numbers though. If it's a shed roof, fitting optimizers down the line may not be such a pain so might want to spend one winter without and then compare and decide.

Also note optimizers are only useful if a few panels are shaded and the rest are not as the optimizers will stop the shaded panel from dragging all other panels down to its level. If all panels are going to get shade then optimizers won't do much.

SD_DRACULA · 05-04-2021 8:21pm

That's what I thought also maybe do without them on the shed since they won't be shaded during the good months and just put them on the roof panels where I have shading from a chimney & a most pointless apex.

New Solar PV installation

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