Solar Panels

[sagalout1954]

Apologies if this isn't the correct forum (or website). Obviously having to deal with sales people, who contradict each other!

First quote for an almost entirely south facing roof (basics of quotes):
12 mono panels 400w
Hybrid 5kw inverter
Give Energy battery 5.2kw

A second company differs from above, panels will be 365w, inverter 3.6kw & 2 x 2.4kw batteries. They are insisting that with only 12 panels & a 5kw inverter "the panels won't work well in overcast days/months".

Without consideration for saving money, does anyone know if a 5kw would indeed NOT work properly with 12 panels? They've suggested I should have 14 if I want 5kw.

Thanks, if anyone can help.

 

[JohnD]

I'm sure you don't mean 5000kW.

What are you going to pay?

Panels will not work well unless it is sunny. Most of your electricity will be generated in summer, when you don't need it.

This is normal.

 

[crappy]

I'm embarking on this same project - for the second time.

You mean 5KW or 5000W - not 5000KW

Yours would work but you would never see the full potential of the inverter. It would still be ok thoug.

12*325 = 3900W
14*325 = 4550W

Adding more improves cloudy days ability to generate and recharge the batteries.

My previous system would on a gloomy day generate around 200W rather than 2.1KW on a sunny day. Technically, they do work but utterly pointless. Having 14 panels - I had 9 - would be better but overkill in summer. You need to be happy with the cost.


Judging but the specs you listed it may well be the same person we're speaking to. I am going for that system.
Batteries charge during the day and discharge at night.

You main consideration should be the ability to recharge the batteries during the day. My house seldom uses lots of power so will focus on battery recharge. Below is over a 24h period.

 

[DiyNutJob]

Replacement batteries will cost you an arm and leg. Then, there is the cost for panel cleaning.

 

[crappy]

Batteries, the li ion ones, are good for 10 years. The only cost £1000 / 2.4kw/h so not terrible when you consider the cost of electricity.
In 10 years time they'll undoubtedly be cheaper.

Cleaning the panels, for the last 12 years I got a hose, broom and once a summer, cleaned them.

 

[DiyNutJob]

Cleaning the panels, for the last 12 years I got a hose, broom and once a summer, cleaned them.

Works if the panels are on a shed. On the roof of a house, could be expensive.

 

[bsr]

Inverter seems overspecified on the first quote. Are you in the UK and what aspects is the roof - South or East/West? 3.68 or 4kW inverter probably fine.

It won't make the system less efficient though, just cost you more money for a bigger inverter.

 

[JohnW2]

Are you in the UK .....

....and what aspects is the roof

..........

... an almost entirely south facing roof ...

Kind Regards, John

 

[snb]

Inverter is 5kw due to combined battery plus panels. They then allow you take up to 5kw from a combination of batteries and panels eg when you boil
The kettle etc. your demand will
Then be satisfied without taking from the grid.

 

[sagalout1954]

Thanks for replies. I've edited my initial post so the kw makes more sense (oops, thanks crappy . Just shows how little I know, husband is better at understanding it, but not a lot!).
Costs have been hovering around £9500 (inc VAT @ 5%), 12x400w Jinko panels, 5kw inverter & 5.2kw battery, both GiveEnergy. This is with GlowGreen but in all of several conversations he 'forgot' to mention we'd need a G99 from DNO & it's not on his full breakdown. When I asked about it he told us they will get that done, BUT there "might" be a cost of £200. Made me wonder if they weren't going to bother as up until recently we didn't even know that had to be done, he had no answer as to why that "possible" cost wasn't on the quote!

In addition, I discover they don't do a pre fitting survey, it's a telephone conversation with "someone". I have asked how they can comply with Local Authority requirements:
Pre installation structural assessment
Post installation electrical cert
Building Regs compliance cert.

Apparently they know from the age of the house (new build 1996), that it will be structurally sound for the load of the panels. The work is contracted out to other companies, for all works done to firms "they use regularly", but I've a problem with not knowing in advance where internal cabling will travel to the fuse box, I've seen it in a neighbours house & frankly, there was a better option than that ugly stuff running along TWO whole walls! All small things making me uncomfortable all put together.

Second company is EEC Solar. Similar pricing for 12x365w JA Solar panels, Solis Hybrid 3.6kw inverter & 2xPylontech UK2000 2.4kw batteries. They do a site visit but are also the ones who stuck that ugly trunking option in a neighbours house!

We're going to wait for a third quote from Spirit Energy, as they service our area & have a really good website, extremely informative. We're both retired so most energy is used daytime, more about being 'greener' than cost saving on the energy bill.

Haven't forgotten to ensure the bird deterrent is fitted!

 

[crappy]

My understanding - while not exactly exhaustive - is that a G9 is if you are going to feed back into the grid.
My system will, by day, charge the batteries, run the house and has it has a sensor on the incomer, try and maintain that at zero - i.e. not feed back into the grid.
I understand then that I would not need that but...I will double check with the installer.

If you have batteries I assume yours would be similar to this and might too not need.

I can see one flaw in my thinking - as it's not a hard disconnect such as a contactor, it could still feed back so it might be that it would be needed.

It sounds like perhaps you need to get an installer who's got vested interest in it and not over-the-phone. Hidden costs and lack of engagement and support might com back to bite you.

As for the weight of the panels, I would not worry. My previous systems was 9 panels @ 20KGs. I suspect the roof was carrying more weight when the roofer and his crew were relaying the felt. 12ish years on, lots of wind and snow, the inside showed no signs of stress, cracks or funny noises.

 

[crappy]

Seems a G99 is

G99 Type-A would be required.

 

[JohnD]

...I've a problem with not knowing in advance where internal cabling will travel to the fuse box, I've seen it in a neighbours house & frankly, there was a better option than that ugly stuff running along TWO whole walls! ....

I plotted out the layout myself and asked the installer if it was suitable.

I have a duct on an internal corner wall running from the loft down into the garage, where I asked for the DC cables to be run; and I wanted the inverter and meter next to my CU and incoming supply (not in the loft where I might have to climb up to look at it). My house has several service ducts and I have the advantage of knowing where they are. I have also laid ply flooring which can be unscrewed and lifted non-destructively for access to services. I might otherwise have accepted trunking in a corner of the kitchen or stairwell which I could have decorated to blend in.

I have no external or visible cables, except in the garage, where the installer used flexible conduit. Trunking is IMO neater and is easy to paint.

The inverter has a cooling fan that runs sometimes. The garage is fairly cool but the loft gets very hot in summer.

When you first get one, you will feel impelled to look at the display and meters quite often. Will luck this desire will reduce over time.

 

[JohnW2]

When you first get one, you will feel impelled to look at the display and meters quite often. Will luck this desire will reduce over time.

Indeed, as with any 'new toy'! However, the desire to look very frequently might rapidly evaporate if/when one discovers that what one sees on the display is 'disappointing'

Kind Regards, John