4kw v 5.1wk system

jrfarrim

Guys,

After some advise. I've got a very competitave quote in from a local Installer for a 4kw system & also a 5.1kw system.

The differance in price is £700, the numbers seem to stack up to go for the 5.1kw system - return 16.8% v 15.6%.

Any other Issues I need to bear in mind before going for the bigger set up.

Thanks
JF

Martyn1981

Quick questions, advice to follow.

1. Are you aware that the FiT subsidy for a 5.1kWp system will be 10% lower than for a 4kWp system?

2. Will the system be capped at 3.68kW? Or does the installer think/hope to get permission from the DNO for larger export?

3. Need more info on £700. It sounds good, but what is the percentage increase?

[Edit: That sounded negative. Apologies. I'm pro going bigger when it makes sense. Extra £700 sounds very promising from a number crunching point of view. FiT drop probably works out breakeven as extra panels won't bump up total price proportionately. 3.68kW cap not as bad as it sounds, 5.1kWp system will rarely sustain more than 4.5kW when hot, and in less than great conditions generation will probably be below 3.68kW anyway. M.]

Mart.

jrfarrim

Yes the calculation is based on the lower FIT rate. The plan would be to get permission from DNO for the larger export.

Talking money, the Increase is from £4899 (4kw) to £5611 (5.1kw), the 5.1kw system would use a Samil 4.4 inverter so wouldn't be capped at 3.68kw.

Thanks
JF

jrfarrim

Also just to add the Installer has Increased the estimated generation between the 2 systems as an exact % Increase.

3250kwh (4kw) Increased to 4160kwh (5.1kw).

Martyn1981

Sounds good.

Mart.

Martyn1981

Just a thought, but if you're thinking of going big, and asking the DNO, then have you thought of going really big?

What is the orientation of the main roof, will all 5.1kWp be going on that? Is there an opposite roof, even if northish? For the relatively small cost increase, you may find 'panelling' that roof is worth doing too. Why?

Well, if you get a bigger inverter anyway (with DNO permission), and are happy to accept the lower FiT, then putting panels on an opposite roof may not require a larger inverter as generation won't peak at the same time.

My 5.58kWp of panels can hit spikes of 4.9kW but will only sustain 4.2kW for any length of time. So theoretically, you could slap 2kWp on a poor orientation roof, quite cheaply and probably get away with a 5kW inverter, if .... big if ...... the DNO will allow you to go over 3.68kW. A Samil 5.2kW inverter will only cost about £40 more than a 4.5kW.

Just a thought.

Mart.

pinnks

I agree. And if you are going big, also consider perhaps going for 330W panels to completely max out, subject of course to DNO approval. On the assumption that the installer is quoting on 250kWp panels, you could go about 30% bigger on the same roof area.


I also wondered why your installer is suggesting a 4.4kW inverter with 5.1kWp array. Seems a big difference even taking account of what Mart says.

jrfarrim

Thanks for some interesting Ideas.

These 2 qoutes are both based on 16 panels on a direct south facing roof (5 degrees off). One with 250kWp panels and the 2nd with 330kWp panels. I don't really think there's much scope to go bigger as the wife has vetoed are thoughts of them going on the front of the house.

I'm 99% sure I'm going to go for the larger option providing we can get approval.

JF

ed110220

jrfarrim wrote: »

Thanks for some interesting Ideas.

These 2 qoutes are both based on 16 panels on a direct south facing roof (5 degrees off). One with 250kWp panels and the 2nd with 330kWp panels. I don't really think there's much scope to go bigger as the wife has vetoed are thoughts of them going on the front of the house.

I'm 99% sure I'm going to go for the larger option providing we can get approval.

JF

Maybe ask her to pay you her share of the lost FIT/electricity savings associated with not using the front roof, and see if that has any effect on her valuation the aesthetics of a panel free front aspect ;-)

jrfarrim

Just about to sign on the dotted line for a 4.96kwp array. Decision has beed made easier by Northwest Electricity. They have advised they will pass anything upto 5kwp, anything over they require 60 days to make a decision & if approved there's likely to be financial cost on my side.

System will be as follows. Does the Inverter sound correct for a 4.96kwp system?

16 x Canadian solar 310w panels (CS6X-310P)
Samil 4.4 Inverter

Cost - £5449

JF

rogerblack

jrfarrim wrote: »

Just about to sign on the dotted line for a 4.96kwp array. Decision has beed made easier by Northwest Electricity. They have advised they will pass anything upto 5kwp, anything over they require 60 days to make a decision & if approved there's likely to be financial cost on my side.

System will be as follows. Does the Inverter sound correct for a 4.96kwp system?

16 x Canadian solar 310w panels (CS6X-310P)
Samil 4.4 Inverter

Cost - £5449

JF

I did some numbers for me a while back based on a local system.
I found that even oversizing the panels by twice! did not cause any great losses.
Then again, I am in Scotland, and a large fraction of my generation is in non-direct-sun.
Assuming 4.4 inverter means 4.4 out - then that'd want 4.6kW in at 95% efficiency, which is only about 7-10% undersized.
Yes, it will lop off the peaks on perfectly sunny summer days, but those are a few hours a year.