Solar Advice please

Chris531

Hi All

Would welcome some advice from those that have a little more experience.

We have decided to make the jump into fitting solar panels at home, we have an east west facing house with no shading issues and enough room to fit a 4kw system. We have received a number of quotes but are awaiting one more.

The two most favourable from local suppliers are coming in broadly speaking around the same price give or take a bit. Both with 16 250W panels.

However the advice I am getting from each is slightly different!, so your views please.

1) One supplier is saying I will generate more with a split system 8 and 8. The other supplier is saying that technically there should be no difference, but what we will see is a more even split of generation during the course of the day. When I plug the numbers into the generation website it comes out with east facing 3010 and west facing 3000, so indicating no real difference.

So as west is at the back of the house the solar panels would be hidden, but I would be prepared to split 8 and 8 and have some on front if it is likely to make a real difference, but if not would have all at the back. We have two kids so most eleccy use is in the afternoon/evening. Any views on the real difference between split or not in the real world?

2) Can I check, is I do split I definitely need a dual MTTP inverter. If the two strings are balanced with same number/type of panels could I have a split system (E/W) with a single MTTP that took the two strings?

3) Finally the two quotes are for different panels/ inverters - one is recommending 8.33 gallium panels into an ENA solar 3.8kw Inverter, the other Axitec black monocrystalline into Fronius Inverter (Single MTTP assuming all panels are on one side, or power one if dual MTTP but this adds £100 - they indicated that by splitting I would not really get my £100 back over 10 years so stick to west facing).

Any views on this set up - panels/inverters (both options would include monitoring etc)? I am being told that the Axitec will likely perform slightly better than the gallium in the first 5 years, but after that the gallium will outperform the Axitec. I can't however see this from the graphs, although the Axitec do have a marginally higher efficiency rating. In reality we are likely to move house at some point between 5 and 10 years, so not really worried on performance after 10 year mark (and recognise with 7 year payback I may not get all my investment back).

One also offered an SAJ inverter but can't find much on those so likely to steer clear.

Apologies for long email but head is spinning and would welcome indication whether there is really any noticeable difference between the options, and if not I will go for the one I feel most comfortable with and his given the better price.

Thanks in advance :-)

tunnel

I'd probably opt for an E/W split personally for a longer generation curve but it really depends on your own habits as to what's best for you. Are you in during the morning/afternoon when generation would be at a peak to utilise the energy at its peak.


As for the panels, can't say I'm familiar with them...Fronius aren't too bad an inverter but don't know of the other and that one would need to be capped at 3.68kw not 3.8(naughty)


What's your location and what prices do you have so far?

Chris531

Thanks

Based in gloucestershire, atleast one of us is at home during the day, then kids after school, washing machine would be mornings, dishwasher during day, real spike will be all day at weekend and after school when computers, tv, x box etc. goes on. Prices a little under £5.5k on that set up. I assume I could go for a 6 and 10 split as well?

Axitec are apparently well known German make, gallium are Spanish company but I think produced in China. Is £100 more for a power one worth it over the frontius do you think then?

Thanks

rustyg

Have you looked into fitting more than 4kW? It sounds like you have enough space for more than 16 panels?

tunnel

rustyg wrote: »

Have you looked into fitting more than 4kW? It sounds like you have enough space for more than 16 panels?

Well spotted!!!
Assuming the west can handle 4kWp(16 panels) then is it safe to assume the east can handle the same...ie 8kWp?
You'd need prior permission from the DNO but well worth looking at as the FiT isn't that much less for 4-10kWp than for upto 4kWp

Chris531

Yes, I did have a think about this, and would make sense if I new I was going to be around for more than 7 years, but the quick calcs I did (back of a fag packet mind you) didn't seem to justify to me the extra capital outlay or hassle of dno etc.? If you think different I'll spend a little more time looking into it though?

Martyn1981

Chris531 wrote: »

Yes, I did have a think about this, and would make sense if I new I was going to be around for more than 7 years, but the quick calcs I did (back of a fag packet mind you) didn't seem to justify to me the extra capital outlay or hassle of dno etc.? If you think different I'll spend a little more time looking into it though?

Hiya Chris and welcome.

Going much bigger, depends what the DNO say, but you'd have no problems going to 5kWp split across the two roofs, and capped with a 3.68kW inverter, so no DNO probs.

But, you'll need to get quotes and do the maths to see if the returns are better or worse (proportionately). The extra 25% in kWp won't increase the cost by 25% but should increase generation by 25%, (good news), but will reduce the FiT by 10% (bad news).

You could consider going bigger than 5kWp on a 3.68kW cap, but will need to consider generation lost to capping. My system (5.58kWp uncapped) often hits and holds 4.2kW in peak summer around 11am to 2pm. But this is only during very good weather conditions, and a little capping isn't as bad as it sounds. Also my roof pitches are 30d (in fact my smallest system is on 20d). If your pitch is steeper then expect shared peak to be a little lower.

Gut feeling, somewhere between 5 and 6kWp you'll get capping, below 5kWp little to none (on E/W).

Chris531 wrote: »

Based in gloucestershire, atleast one of us is at home during the day, then kids after school, washing machine would be mornings, dishwasher during day, real spike will be all day at weekend and after school when computers, tv, x box etc. goes on. Prices a little under £5.5k on that set up. I assume I could go for a 6 and 10 split as well?

From what you describe, I'd definitely consider a split system.

There will be flexibility over the scale of the split. The smallest string will need to meet the minimum voltage required by the inverter, and the larger string will need to be within the max voltage. Your installer will be able to choose an inverter that meets the split, and can also choose panels based on their voltages to increase or decrease (as necessary) the voltages to meet the inverter parameters.

But, 6/10 shouldn't be a problem (I suspect). Might only need tinkering when you get to 5 or 4 panels.

Chris531 wrote: »

2) Can I check, is I do split I definitely need a dual MTTP inverter. If the two strings are balanced with same number/type of panels could I have a split system (E/W) with a single MTTP that took the two strings?

Nope, single MPPT won't work, it stands for maximum power point tracker. If you have two strings (matched or otherwise) going into a single MPPT, then it will look for the maximum SHARED power point to lock onto (track). So if one string is (for simplicity, made up numbers) generating 5 and the other 15, then the shared max point is 5, so the lowest string will drag down the higher string. This would happen all day*, with the west dragging down the east in the morning and vice versa in the afternoon. [*There may, for pedantic arguments sake be a small sweet spot somewhere in the middle.]

Mart.

tunnel

By your own figures(roughly(back of wine bottle(don't smoke)),
4kWp E/W
3000 x £0.1438 £430
1500 x £0.0477 £71
Total £501


8kWp E/W
6000 x £0.1303 £780
3000 x £0.0477 £142
Total £922


Going on those figures I'd say if you could get an 8kWp system for around £9k or less(doable) then its a better return than the 4kWp that will cost you over £5k


Don't worry about DNO, any installer worth their salt will get you the approval within a month, leaving enough time to get the install done before the FiT drops again in January

Chris531

Thanks, that certainly helps on the inverter, split and sizing.
I think the numbers on 4 vs 8 probably show what I assumed, that the payback period will broadly speaking be the same on both, and the real financial benefit only starts to make a difference after this, so c year 7ish onwards. So if I was definitely staying put after this I would do, but I will get some quotes on the larger system just to double check return.

Thanks all

Living_proof

I had a split system installed in March and have been very happy with the results. I have 2kw east, 2kw west and I did consider having 4 on both but now my family are away the benefits of the free electricity are less and the cost would have been about half as much again. My advice would be in your own circumstances to go for the maximum number of panels you can and reap the benefits of being able to access free power throughout the day. If you can divert excess capacity to hot water, so much the better - but I don't have an immersion and little hot water requirements.

JTPR

tunnel wrote: »

By your own figures(roughly(back of wine bottle(don't smoke)),
4kWp E/W
3000 x £0.1438 £430
1500 x £0.0477 £71
Total £501


8kWp E/W
6000 x £0.1303 £780
3000 x £0.0477 £142
Total £922


Going on those figures I'd say if you could get an 8kWp system for around £9k or less(doable) then its a better return than the 4kWp that will cost you over £5k


Don't worry about DNO, any installer worth their salt will get you the approval within a month, leaving enough time to get the install done before the FiT drops again in January

Within a MONTH?! Ha, any installer worth their salt will have it sorted in 2 weeks max.