Which panels and inverter to choose?

[zcacogp]

Hi,

This is my first post, and I'll come clean at the outset; I'm not an electrician nor a solar installer. BUT I am in the process of getting an install, and would like some help in choosing the best option. I have found an installer whom I like, and whom I trust (I was recommended to him by a longstanding friend) and he has provided me with three quotes for three different systems. I will discuss the quotes with him directly as I am sure he will be helpful, but in the interests of not taking advice from someone trying to sell you something, am asking here as well.

The three quotes are as follows;

1. 14 x Suntech STP190Ad panels. 1 x SMA SB2500HF Inverter. Size = 2.66kWp. Cost = £8830. ROI 11.6%
2. 14 x Sanyo HIT SE10 235Wp panels. 1 x SMA SB3000HF Inverter. Size = 3.29kWp. Cost = £12450. ROI 10.2%
3. 13 x Azur P235 panels. 1 x SMA SB3000HF Inverter. Size = 3.055kWp. Cost = £11183. ROI 10.6%

As I understand it, the Sanyo panels may be more efficient than the others, and their output estimate will therefore possibly to be more conservative than the others, hence things may look better with them than quoted. The Azur ones have a fancy coating which means they will degrade less over time than the others (guarantee of 98% efficiently after 20 years, as opposed to 85% with the others.)

I guess that looking at the figures in more detail will tell me why the smallest system gives the best ROI, and I haven't done that yet. BUT, putting the question simply, which of those panels is the best bet? I know nothing about solar panels, and am struggling to find any reasons to choose one over the others on t'interweb. Everyone seems to be talking about the Sanyo panels, and the friend who recommended the installer to me has them as well, but why are they so popular? They offer the lowest ROI of the lot!

Which quote would you go with, and why?

Thanks for any advice you can offer.


Oli.

 

[SolarCity]

Hi Oli,

If the installer has, as I assume, given you figures based on SAP calculations then the benefit of the Sanyo panels will not be immediately clear. Judging by the sizes of the systems, space is limited on your roof - hence the larger Sanyo system (higher efficiency means more watts per square metre). It is likely that the Sanyo system, when run through analysis software, will give a much better return than what has been suggested.

The Suntech panels are also an excellent choice - fantastic value for money. If the installer is offering you three different choices then the chances are that he will be very likely to give impartial advice. Ask him his opinion because it seems like you should be able to trust him. The prices are also excellent.

 

[BruceB]

A couple of other metrics you might want to calculate to help you decide:

- Cost per kWp of panels installed
- Profit after 25 years

You then have to take a view on:
- whether you have the money to invest now without borrowing
- whether you believe that the regime will continue to pay out for 25 years
- whether you can delay your gratification until then
- whether you want to maximise the size of the array in kWp terms (might depend on money available to invest and your own usage patterns)

In the end though you have to work out what is important to you

Regards
Bruce

 

[Worcester]

@BruceB,

Rather than using cost per kWp, I would suggest cost / kWh is a better metric.

Seeing as he's suggesting SMA, why not run it through both Sunny Design and PV*Sol to compare the predicted kWh outputs.

 

[zcacogp]

Guys,

Thanks for your replies.

BiggsSolar, the usable roof area is limited, yes. Shading and bits of roof pointing in the wrong direction are the problems. Thanks for your helpful comments about the installer; he comes on high recommendation and I liked him when he came to visit and see the roof. I'm not quite sure why the Sanyo panels are better; from what you say, it sounds like they produce more power for a given area, and hence make better use of smaller areas. I don't know what a SAP estimate is, or why Sanyo panels would do better when looked at with analysis software. Although, from what you are saying, the Sanyo system would be a good one to choose.

BruceB, thanks, those are good metrics and I'll put the numbers into a spreadsheet and poke 'em around a bit. Is it likely that the scheme will cease to pay out within 25 years? 'Tis government-backed so should be as safe, but it does look almost too good to be true ... ! Another one; why would I want to (or why would I not want to) maximise the size of the array in kWp terms? I do need to work out what is important to me, but don't understand the difference implications of the different options.

Worcester, thanks for your comments. Cost/kWh is an interesting metric; how would I calculate that? (As in, how do I calculate a kWh figure?) I am guessing that Sunny Design and PV*Sol are analysis software packages such as mentioned by BiggsSolar - non?

Thanks for your input, everyone.


Oli.

 

[Worcester]

@zcacogp You can download Sunny Design for free from the SMA website Software. SMA Solar Technology AG

Put in the key parameters and it will take account of the different panels claimed efficiencies and hence give you an annual kWh estimated output for each of your combinations.

 

[SolarCity]

If Sunny Design is a bit complicated, I'll run all three set ups through PV Sol and see what results I get. This will give you an estimated annual kWh hour return on each system, taking into consideration location and panel characteristics.

The Sanyo panels are better, not just because of their high efficiency (which literally refers to watts/square metre) but because of their other characteristics. They perfrom well in hot conditions (panels efficiency drop as the temperature rises) and well in low light conditions. These characteristics often make them a more economic choice on some systems.

Generally, the larger the system, the more economic it is. The labour and materials on a 3kWp system, for example, are not twice as expensive as a 1.5kWp system - but the yield will be.

 

[Surboy]

Personally I would choose the Suntech panels (soon to offer a 10 year warranty), Sanyo panels are totally overpriced and overrated and only make sense in very small roof spaces. As for Azur, I have never heard of this brand although it does sound like an OEM product to me...Suntech modules are good overall performers.

 

[BruceB]

Agree that Worcester's suggestion of cost per kWh output is a better metric than cost per kWp installed. It does rely on your modelling software though.

I do not want to raise too many worries about the 25 years. But Governments can always change their mind and are not bound by their predecessors. I have a pension from my time in Government service that is due to give me a lump sum when I hit 65 in 2020. The change from rpi to cpi means that it will be worth significantly less than I could have expected 2 years ago. The change was retrospective. Just pointing out in hard times Governments can do anything.

You might want to maximise the size of the array up to the 4kW tariff boundary on the basis that investing more gets more absolute return.

Regards
Bruce

 

[Surboy]

Couldn't agree with BruceB more. Also bear in mind that it is forecated that the UK will reach grid parity in 2016 or so and there will be greater emphasis on storing than feeding into the grid...maximise the array with a reasonably priced good performer module...

 

[langstroth2]

Some very useful words of advice here (thanks). I've a similar problem; I won't go for the cheapest quote, but rather the one I consider represents best value (over time) - i.e. a trade-off between budget, good quality equipment and installation. Installation quality I can only go on recommendation / evidence of happy customers. Quality of equipment is the problem. Of the several quotes I've received so far most recommend one of the well known Inverters, but interestingly none have quoted for Sanyo - it's a mixture of Mitsubishi; UpSolar or Sharp.

Space is not particularly an issue. How to compare - any comments on these panels.

Should I get hold of the relevant panel stats, download the SMA software and look at generation totals over 25 yrs. Or is this frankly like worrying over the type of tyres on a new car when it's the engine efficiency (=good inverter?) and general build quality (=quality of install?) that'll have greater impact on total cost of ownership.

 

[SolarCity]

If you let me know that different specs of the installs, I will run them through PV Sol Expert and give you some figures. Let me know where you are in the country, orientation of your roof and I'll give you a rough idea.

UpSolar are good value. Sharp are very average, Mistubishi not much better. I'm going on potential yield according to design software, not just my opinion.

The reason you haven't been quoted for Sanyo, I suspect, is that they're much more expensive than other panels. Installers are required to give you calculations based on the SAP calculations - a calculation that makes no consideration of panel quality. Therefore the advantage of using Sanyo would be lost on the customer.

 

[BruceB]

My personal view is that as there are no moving parts on panels then provided they come with comparable warranties it is difficult to place one above the other on the basis of good evidence. Some will disagree though and say dig out independent performance reports.

I do think you want an inverter company that is likely to be around for a long time, is from a country with a sound economy and with a good support network. A well known German company looks good from that perspective! I do not to raise doubts about specific companies but there are a few countries in the eurozone with economies in ---- state at the moment.

If you want a Sanyo quote then ask for it. An installer will appear very expensive if he offers it. Sanyo panels are to me 40-50% more expensive than say Upsolar. I normally now include them as an option. On an average 3-4kW domestic that I have been quoting for then Sanyo adds many thousands, increases the payback time by up to a percent, reduces rate of return similarly, but over the course of 25 years FIT income makes more absolute profit by many thousands. So it depends on what the customer is trying to achieve, their motivations and whether they trust the regime to continue for 25 years.

Regards
Bruce

 

[langstroth2]

Thanks for the quick replies.
BiggsSolar, thanks for the kind offer - specs as follows (South facing roof, southern England, shading across roof due to tree to west of roof from ~6pm BST, edit: roof is at an angle - ~25-30 degrees I would guess).
1) 16 x Upsolar 240W, SMA SB 4000TL
2) 16 x Mitubisi 250W, SMA SB 4000TL
3) 16 x Sharp 245W, Kaco Powador 4202

I also had this one, but that was before I decided a larger array would probably represent a better longer term set-up....

4) 10 x Sharp 185W, Sunny Boy 1700W

 

[SolarCity]

Okay, these figures are based on Salisbury and I've not factored shading into the calculations.

Option 1) 16 x Upsolar 240W, SMA SB 4000TL - 3,426kWh annually
Option 2) 16 x Mitubisi 250W, SMA SB 4000TL - 3,352kWh annually
Option 3) 16 x Sharp 245W, Kaco Powador 4202 - 3,251kWh annually

As a comparison, I also ran 16 x Sanyo 250w panels on a Fronius IG TL 36 inverter. This produced - 3,686kWh annually. But as Bruce has mentioned, these are far more expensive than other panels.

UpSolar have a pretty good reputation and they're very good value.

 

[langstroth2]

That's very helpful, thanks. Noted re: not factored in shading.

So if my maths isn't t'pot over a 25yr lifespan of operation there's a 435kWh/yr = 10,875kWh difference between the best set up (Sanyo/Fronius) and less well performing set up (Sharp/Powador), which equates to an extra ~£4,458 of FiT payments (ignoring bill savings, increase in FiT etc) ...which is an eye opener...

The question is whether the difference between the Sanyo and Upsolar warrants the additional cost:
260kWh/yr difference = 6500kWh = £2665 (which is probably conservative given the aforementioned ignoring of FiT increase, exports etc)

Food for thought

 

[SRE]

I've found that most panels produce 200 ish kwh extra a year when matched with either the Power One inverter or the Fronius TL. Both have excellent warranty offers at the moment as well as getting more out of all panels. I've stopped offering SMA now, they just can't compete with the other 2.

 

[SolarCity]

Indeed. I use the Fronius IG TL inverters more than any other inverter - the lack of personal display makes them unsuitable for some customers, however.

 

[liquidity]

I've received a quote for a system with 16 Sharp NU-E245J5 and a Power-One PV1 3.6 for 12K. Predicted output is 3831 kWh/year. Enecsys micro inverters would add 10% to the cost. There is some shading on the eastern third of the roof in the morning. Any comments on the value for money and choice of components would be appreciated.

 

[SolarCity]

I'd seriously question those output figures. Whereabouts in the country are you?