Solar newbie needing help choosing best option

[Falz87]

Hi all,

I'm new here and would appreciate if you could guide me into choosing the best investment for a solar panel system. I have limited knowledge and technical experience, and therefore what could be obvious for anyone might not be for me

I have had a couple of home visits from different companies to install a 10 panel system on the rooftop, which give various daily/yearly output units with different brands and inverter types and would appreciate your feedback on the best choice.

LG Panel 320W - 10 panels - String Inverter (ABB) output of 13 units per day ****
LG Panel 300W - 10 panels - Micro Inverter (Enphase) output of 13.5 units per day ****
Canadian Solar Or SolarWorld 290W - 10 panels - String Inverter (SMA) output of 12.5 units per day [same panel with SolarEdge inverter outputs 14 units per day]

**** These panels are bi-facial. They are able to provide around 25% more output daily due to their back panel.

What do you think is the best combination of Panel and Inverter? I have heard positive things about Enphase as well as negative ones. SolarEdge looks good as well but a little on the expensive side.. therefore your thoughts would be appreciated.

A couple of few more questions/concerns..

1. Is it safe to assume that the main daily/yearly output is dependent on the inverter? Since panels with same specs but different inverter brands seem to vary on these units

2. Would you recommend LG for PV systems? They have new panels which are bi-facial, that are able to generate power even from their back panel, however some companies seemed against it as the transparent back panel on the 300W panel gives problems. Any one knows if this is true?

3. Micro-inverters seem to have better benefits over a string inverter, however the cost tends to also be higher. Which would you recommend?

Thanks in advance

[solar pete]

Hello Falz87 and welcome to Solar Panel Talk. Panels are panels (in my opinion) and I wouldnt bother with bi-facial. I only recommend micro inverters if you have shade issues.

1. Not really different companies will suggest different yield based on what is known it will easily produce, generally knowing they will produce a bit more, this allows for some panel degradation.
2. If it were me I would be going with Canadian and SMA combo, we have installed thousands of systems and have settled on this as our favorite combo.
3. Micro are as yet un proven over the long haul, lots of failure points out in the elements.

Opinions vary, keep reading and good luck with it, cheers.

[solarix]

Well, you have left out the prime criteria of cost. A kWHr of electricity is the same no matter how it is generated, and the standard way to compare systems is to compare the $/watt for each proposal. In general, microinverters have the potential to be more productive, but really only help if you have shade problems to contend with - however, they also have a big reliability risk and are more expensive. The high-efficiency panels are also high-cost and high $/watt and are really only justifiable if you are constricted on roof space.
The "25% more output" for bifacial panels should be read as "up to 25%". Getting this much additional output depends on an installation where a lot of light is reflected to the back side. Like if you have a porch cover made from these panels with a white floor underneath.
The main difference between inverter types is how well they handle partial shade conditions. If you don't have shading, then all inverters will have remarkably similar results. If you read the SolarEdge literature - they are careful to always say "up to" 2% more production due to panel mismatch etc. In reality, you won't be able to measure the difference.
My advice is to go with the most reputable installer that offers you the most watts for your dollar. Probably going to be the Canadian Solar/SMA.

[littleharbor]

You mention Panels on the rooftop. If these panels will be mounted flush on a typical pitched roof There would be no reason to use bi-facial panels. If you place bi-facial panels on this type of surface you might as well derate them by 25 percent. I would say any contractor trying to sell you a setup like this is just concerned with making the most money he can off your job and is not to be trusted.

If you don't have any shading issues on your roof your best bet would be the central string inverter.

[J.P.M.]

You are indeed a babe in the solar woods.

Best guidance I can give to you at this time is a strong "Don't buy anything yet !!!", followed by "Question everything everyone tells you until you understand it."
You can become fairly knowledgeable, fairly quickly. Start with self education. A few hours of learning will pay big dividends. You will quickly be on a path to unlimit your knowledge and gain more than the technical expertize necessary to make intelligent, more informed choices.

For starters, if you're thinking about off grid, batteries, etc., and have access to grid power, give it more thought and more information gathering - off grid or just grid tied with battery backup usually involves a change in lifestyle most folks are ignorant about and probably not willing to make, not to mention a great increase in monetary cost for power. It's not for most folks. If you think it will save you money - it most likely will have the opposite effect.

Then, if you are grid tied:

1.) Learn how you are charged for electricity by your POwer COmpany (POCO). Cost is usually the final and often the only determinant in a choice to get residential PV. If the long term cost of a PV system is greater than the cost of the POCO supplied power the PV system replaces, the PV system is, by some definition, not cost effective (See prior sentence, QED) .

You'll need information about POCO tariff structures and options before you can make an informed PV go/no go decision for the economic part of the decision process.

2.) Download (for free) a slightly dated version of "Solar Power Your Home for Dummies" from the net, or spend ~ $ 20 U.S. or so on a mostly current hard copy. I'd pay particular attention to the parts about energy conversation. Reason: The impetus behind most of the home PV craze is about saving money - not saving the planet. (Fortunately, saving money on electric bills - at least in a cost effective way - helps the planet in a verifiable way).

In that context (That is, energy reduction minded rather than PV for its own sake) the way to save the most money is generally to first do the stuff that saves the most for the least amount spent - that is, most bang for the buck first. In that contest, solar PV is way down the list of options to save money when compared to things, in some very loose order and examples only, from merely turning stuff off (cost == zero, payback immediate, BTW) to replacing stuff with more efficient stuff (generally start w/ small items like light bulbs before scrapping out an old but functioning HVAC unit), and upgrading insulation and building sealing before new A/C.

Mostly because of the herd mentality, advertising hype and other things that work to separate fools from their money, solar is usually the first (and often the last and only) thing most well heeled homeowners do to reduce electric bills. That's usually and precisely backwards from the logical order if cost effective reduction of electric bills is the goal.

BTW: A PV system will be smaller (read less expensive) if sized to an electric load made smaller via use reduction and conservation. Win-win. Doing use reduction and conservation AFTER a cost effectively sized PV system only serves to make that system less cost effective, and perhaps oversized.

If I have a boat with a leaky hull, I'd probably think about fixing the leaks before buying a bigger bilge pump. Just sayin'.

3.) Download and get familiar with something called PVWatts from NREL. It's a residential PV modeling program that helps homeowners estimate how big of a system they may require. Just read all the help/info screens a couple of times, get your possible solar array orientations mostly correct and after a few runs, reread the help/info screens again. It's a quick learning curve. You'll more than likely zero in on a array size. Small caveat: Don't put a lot of faith in the electricity saving estimated by PVWatts. GIGO. do your own rate and savings analysis. It's a bit of a PITA doing it that way, but the PVWatts savings numbers will send you down the wrong road.

Not much, if any of this is rocket science, but it does take some effort on the part of homeowners to get a safe, fit for purpose system, or determine that it's not cost effective by their hopefully informed criteria.

After you do your homework, come back here to fill in any knowledge gaps you still have. Doing it that way will make your questions better, you'll get better answers and a lot of time/effort will be saved.

Not my $$, house, life, but I'd not waste my time just yet being B.S.'d by solar peddlers who make money by putting product on your property - not saving you money. Besides, after your self education, you'll probably know more than most of the slugs who will try to peddle cost INeffective stuff to you, and thus having denied them the tool of homeowner solar ignorance they use on most other homeowners. (My apologies to posters and readers of this forum who sell/install solar who are not slugs)

Welcome to the neighborhood and the forum of few(er) illusions.

Take what you want of the above. Scrap the rest.

[Falz87]

Thanks guys for your detailed feedback. I will post an update/replies to the main questions you all asked as I might have omitted some important info.

From the impression I had, this forum seems to be more inclined towards USA? (Just the impression I got while reading certain forum posts).. I am from Europe/Malta .. we pretty much get around 300ish days of sun a year, and the solar panel installations are normally done this way (picture in the link below):

http://www.pveurope.eu/var/pepper/storage/images/news/solar-generator/solar-panel-producer-luxor-solar-flew-below-the-radar-and-continues-to-grow/9475-1-eng-GB/Solar-panel-producer-Luxor-Solar-flew-below-the-radar-and-continues-to-grow_full.jpg

Therefore, seeing the sun factor & inclination of the panel might make the 'bi-facial' feature slightly more attractive above the others?

As for the prices, I'll update the specs above with the prices to get a better indication of the packages. (Prices are in Euro and include installation/supply etc, however seeing the current exchange rate, they're pretty similar to the USD price).

LG Panel 320W - 10 panels - String Inverter (ABB) output of 13 units per day **** EUR 7000
LG Panel 300W - 10 panels - Micro Inverter (Enphase) output of 13.5 units per day **** EUR 6500
Canadian Solar - 10 panels - String Inverter (SMA) output of 12.5 units per day **** EUR 6500 [SolarEdge adds an extra EUR1,000]
SolarWorld 290W - 10 panels - String Inverter (SMA) output of 12.5 units per day **** EU R7300 [SolarEdge adds an extra EUR1,000]

Therefore seeing the above rates, the LG seems to be the best option due to price, units (possibly gain a bit more due to bi-facial, even though it might be a marketing technique?), factor of shade to consider.. but then it was mentioned that Micro inverters have a tendency to give more problems?

As for what J.P.M pointed out, I have taken some necessary steps to building the house with fully insulated blocks and thermal insulation roofing together with energy saving lights to reduce the load of electricity, however there is a government rebate that offers a good refund of the total package, and pays for the extra units you generate which are not consumed. Therefore, having worked it out it does sort of pay out after a certain number of years. (Also due to the fact that we get a lot of sun on our island throughout the year)

The issue is that since its a hefty amount, I would like to make the proper choice if I decide to install the PV system since the roof space is limited, and obviously installing the system would be something of a long term investment.

Thanks again

[J.P.M.]

Before anything else, be very careful about what you believe about bifacial panels. In any practical application, including such as the one shown in your photo, it's more likely that any "extra" output from irradiance to the backside of a panel will be limited to much less than a 25 % increase - that amount of enhancement is - quite simply - B.S.

Reason/logic: Any increase in output will be no more than the ratio of frontside to backside insolation a panel receives. Period. The backside of most panels in most practical applications and common orientations will be from zero to MAYBE, and at best, 20-30 % of the reflected and diffuse radiation that the frontside of the panel receives, with that reflected and diffuse radiation itself being MAYBE 10-20 % of the total radiation the frontside of the panel receives.. So, the backside of a panel with a common orientation will see perhaps ( 0.25 X 0.15) ~ = 0.04 of the frontside radiation, with a lot if not all of that radiation being diffuse in nature and also hitting the backside of the panel at relatively high incidence angles, both of which factors work against any form of efficient absorption by the panel.

Folks who claim 25 % enhancement in either irradiance, day long insolation, or output usually use very optimized and theoretical situations and orientations that are rarely seen or even achievable in practice. Note the caveat "up to" that usually accompanies the claims. "Up to" my butt. It's B.S.

Believe what you want, but based on having been around solar devices for a long time and having spent a lot of time learning about and measuring the solar resource since the late '70's along with the various paths and penalties associated with reflected solar radiation with respect to how it can (or can't, or won't) be scattered, concentrated and/or absorbed, and for this thread, as well as the paths to the backside of a collector in most any orientation, much more than a 5 % enhancement in output is a real stretch for me, and only then at a high tilt angle with snow cover about half the year and reflecting mirrors behind the panels.

Unless the price is no more than +5 % for any bifacial panel vs. the identical panel that's monofaced, to me it's no more than another way to separate fools from their money.

For guesses (and anything dealing with future conditions is by definition a guess, even if educated) at optimum system size and cost vs. estimated electricity costs and possible savings using some idea of the time value of money with respect to solar improvements, again NREL has some interesting stuff. Root around on their website and search under "LCOE". That's one way of several to use life cycle costing and time value of money techniques to make a "SWAG" = Scientific, Wild-Assed Guess" at determining cost effectiveness.

FWIW, PVWatts shows a site for Cyprus at Larnaca. The rest of the island may be similar in terms of solar climate. Check it out. You'll probably get as good an estimate or better than from local peddlers. At least you'll have a method of comparison. Looks like you can get about 1,500 - 1,600 or so kWh/yr. per installed D.C. kW of solar panels. One more time: Read the PVWatts help/info screens first.

Good luck.
Read the book and study/learn PVWatts. You've got nothing to loose and a lot to gain, if only knowledge. Avoid B.S. of bifacial panels unless the price is right. The additional performance will be slight.

[jflorey2]

Therefore, seeing the sun factor & inclination of the panel might make the 'bi-facial' feature slightly more attractive above the others?

Not in that case. In cases where the panel shades the area behind it you see little benefit. About the only times you'll see a significant increase in power output with bifacial panels is when the panels are high above the surface AND the surfaces nearby are reflective. For example, there's a restaurant down by the water here that has bifacial panels in an awning ~10 feet above the floor, and there's a lot of reflection from the water. In that case it might make sense, but for a roofmount (or even most ground mounts) you won't see much change.

That being said, there's nothing wrong with them - and if they come at the same price as one sided panels, no reason to avoid them.