Solar PV questions

Davidb4

Hi all, currently getting quotes for solar pv. I have enough space for 16 panels so am looking at 4KW array. I have no shading apart from a chimney which will only be affected at the very end of the day. My roof faces SSE and is 35deg I think.

Is there any benefit in micro inverters? One of the sales guys said that they are 10-15% more efficient and start earlier and finish later? I am tempted by the longer warranties, will string inverters really fail after 10-12 years? Anyone know of a string inverter or micro invertor that has failed?

I have read a number of horror stories about solar edge and the parts failing due to water ingress. Is this fair?

I've seen the thread on iboost and am interested in this too. My quote says this will save me £250 a year which i now see is rubbish. Are they worth it?

Sorry lots of questions but i think i'm getting there!

tunnel

What sort of prices have you been quoted so far? How much to include the iboost? What sort of returns have you been quoted from a 4kWp system?
As for solaredge, I can't fault it, had one of my systems retro fitted with it nearly 2 years ago and it does exactly what it says on the tin.
If there's only minimal shading a dual MPPT string inverter should suffice anyway. So many questions


If your prices are over £5k then may be an idea to post your rough location on here, that way you might get some recommendations for installers that aren't in it to shaft you!!

Martyn1981

Hiya David. If you have a SSE roof, then it'll very slightly favour the morning, so end of day shading may not be worth worrying about. Keep an eye on it now during a sunny day, and see how much shading there is. Take some photos if it's bad, your installer may be able to shift panels slightly to avoid that patch, or use 14 285Wp (ish) panels to again avoid the area.

But if only minor then as T says, a dual MPPT inverter with all the shaded panels on one string, or even a single MPPT inverter (2 strings will have to match) with all the shaded panels in the same string.

Nothing wrong with SolarEdge power optimisers, or micro-inverters, but there will be more kit, on the roof, that could fail. Yes, they probably are more efficient, even without shading, but 10-15% may be an exaggeration. However, consider the return on investment, if they add £500 to a £5000 install, then you'd need 10% more generation just to make up for the increase in capital.

If you have serious shading, like my WNW roof, then they work brilliantly, but for minor shading, especially what you describe, then probably not worth the hassle.

String inverter life expectancies might be in the 10-12 year range, but it's really hard to know. Some of the manufacturers are suggesting longer, perhaps 20yrs, but not sure what that really means unless they increase their warranty lengths. Looking at a cheapish, but decent 4kW Samil inverter, that'll cost about £500 (to the installer) and come with a 10yr warranty.

I've heard of inverter failures, but those were under warranty. Have you heard of the bathtub curve for leccy items - large failure rate at the start (under warranty) as some substandard kit escapes the factory, then a long low failure rate (bottom of the bathtub), followed by a steeper rise later after life expectancies have been reached and the kit ages.

Mart.

Davidb4

Prices so far are:
1. £6500 for solar edge with 14 285W Sunedison panels and including iboost (£500).
2. £6700 for 14 Sunedison 280W panels with enphase micro innverters including iboost.
3. £6200 for 16 250W 833 panels and Growatt inverter including iboost.

I live in North Hampshire. I'm favouring the first 2 at the moment!

I really like the enphase monitoring. I think the solar edge is similar but haven't seen it working.

I also have a garage attached to the house (facing SW) where i could fit extra panels in the future when the budget allows. I would be classed as a high user as we have an electric car.

lisyloo

FWIW - I have solar edge and I'm happy with it.
I also have a iboost and I reckon it saves about £50 per annum and I have tried various suggestions around thermostats.

Personally I don't think they are worth it because the pay back time is long compared with the life expectancy and there's a risk it's longer (I think they are only guaranteed for 2 years).

rustyg

lisyloo wrote: »

Personally I don't think they are worth it because the pay back time is long compared with the life expectancy and there's a risk it's longer (I think they are only guaranteed for 2 years).

They are certainly worth it if you have an older boiler or use a more expensive way of heating your water.

Just because a device has a 2 year warranty doesn't mean it's going to fail after 2 years.

lisyloo

They are certainly worth it if you have an older boiler or use a more expensive way of heating your water.

Sure.
I was working on gas at about 5p per kwh.
My bad.

Just because a device has a 2 year warranty doesn't mean it's going to fail after 2 years.

Agreed.
But I think it's an indication of expected life.
Replacement/repair cost has to be factored in and expectations for the iboost with a 2 year warranty would be different from panels with a 25 year warranty or an inverter with a 10 year warranty wouldn't they??

Martyn1981

Davidb4 wrote: »

Prices so far are:
1. £6500 for solar edge with 14 285W Sunedison panels and including iboost (£500).
2. £6700 for 14 Sunedison 280W panels with enphase micro innverters including iboost.
3. £6200 for 16 250W 833 panels and Growatt inverter including iboost.

I live in North Hampshire. I'm favouring the first 2 at the moment!

I really like the enphase monitoring. I think the solar edge is similar but haven't seen it working.

I also have a garage attached to the house (facing SW) where i could fit extra panels in the future when the budget allows. I would be classed as a high user as we have an electric car.

I think those prices are a little high, not horrendous, but hopefully you can do a little better.

The Iboost is £200+VAT retail, so the installer will pay less, and as part of the PV install VAT will be 5%, so it shouldn't really add more than ~£250 to the deal.

Have a think about that garage roof now. Is it a big/small roof, how many panels would fit? Small PV installs cost proportionately more, but adding to a job, costs proportionately less, so it might be worth pondering it all now. You also have to think about DNO restrictions if you hope to exceed 3.68kW in output. That's inverter output, not panel totals. So .....

if you go down the micro-inverter route, you may have to stop at 3.68kW unless you get permission to go bigger. But if you go with SolarEdge, you could fit a 3.68kW capped inverter, but run more panels through it. So you'd probably want to think about this before committing one way or the other.

If the orientation of rooves is very different then you can run quite a lot through a smaller inverter, as they won't peak at the same time. In your case SSE and SW aren't massively different, but this would help a bit, and there may also be a difference in roof pitch too (?) which would also allow you some wiggle room to run more panels through a 3.68kW capped inverter without having to ask for permission to go bigger ..... which you might not get, and has to be got before work starts. Whereas for 3.68kW systems, you simply install, then notify the DNO afterwards (within 28 days).

[Edit: Should have mentioned, the FiT rate for bigger systems (4-10kWp) is 10% less. M.]

Mart.

Caan

Some decent advice there David, dropped a message to your inbox. Would just add, with the current DNO restrictions you'd be better sticking to 4kW, if you're car charging at home anyway you'll see a far better return on your system than the average user. Nice and sunny in Hampshire too! :cool:

Stawmn

We had Scottish solar in for a quote and they recommended buying a timer for the immersion and setting it to come on for an hour at about mid day. Rep says that the water would be heated sufficiently and initial outlay would be about £12 as opposed to the iboost at £300. The saving would be the same, but the initial outlay is much smaller with a timer.

However, we have the water heated by gas as we're up and out early in the morning. There wouldn't be any solar at that time, so smart management of the gas plus the timer might be a better/cheaper option.

Martyn1981

Stawmn wrote: »

We had Scottish solar in for a quote and they recommended buying a timer for the immersion and setting it to come on for an hour at about mid day. Rep says that the water would be heated sufficiently and initial outlay would be about £12 as opposed to the iboost at £300. The saving would be the same, but the initial outlay is much smaller with a timer.

However, we have the water heated by gas as we're up and out early in the morning. There wouldn't be any solar at that time, so smart management of the gas plus the timer might be a better/cheaper option.

Hi.

The difference is that the iBoost (or similar) only diverts excess generation. The simple and cheap idea of a timer switch is that if you aren't generating much, or less than the immersion draws, then you'll be buying leccy.

A compromise might be to install a lower power immersion, say 1kW and run it (again on the timer) for 3 hours, say 11am to 2pm. That way there might be a better chance of generation exceeding immersion draw. But it will still be luck of the draw.

Regarding your early morning showers, that doesn't really make any difference. The water will be cooler (after the showers) it then gets heated by PV generation (hopefully) during the daytime. If there is any shortfall in tank temperature then the boiler can kick in, in the early hours or whenever it usually does to top up. the only time you'd want to avoid the boiler re-heating the water would be after the showers, but before the PV day.

Mart.