Price of Solar Panels - Page 1
Forum section: electronics / general

author: fastbike
author_rank: Regular Contributor
timestamp: August 19, 2024, 09:11:24 am
content: Soo, I'm learning reasonably quickly - I hope. Well, I know a lot more than I did at the end of last weekThe biggest lesson today has been for the price of panels, bear in mind I'm in New Zealand so far from a densely populated country where economies of scale should kick in.My initial pricing was for LONGi Hi-MO LR5-54HTB 440W solar panels. The price on the website of the supplier was for NZD$320 per panel. Ordering qty 24 gave me a better price of $269 per panel but with a $400 shipping charge (so effective price of $285 per panel).A bit of googling found a local supplier of Trina Vertex S+ - TSM-435NEG9RC.27 panels (435W). He can supply at $152 per panel, but I have to buy a full pallet of 36. I can do the collection myself (approx 750 kg), and am negotiating with a friend to buy the surplus 12 panels at cost.So that is $6856 vs $3648, a saving of $3208 (47%) on a 10 kW array. I'm assuming the panels are of similar quality - the specs for output at 25 years show approx 87% of original performance for both.Are there any fish hooks I should be aware of ?

author: tunk
author_rank: Super Contributor
timestamp: August 19, 2024, 02:17:18 pm
content: Wouldn't know about the panels, but it's half price andif something goes wrong, you have a door to knock on.Maybe do a web search and see if it's a reputable vendor.

author: tszaboo
author_rank: Super Contributor
timestamp: August 19, 2024, 02:28:00 pm
content: LONGi Hi-MO LR5-54HTB :These panels area sold for 70 EUR- 90EUR + TAX here. So that's max 180 AUD including 20% or whatever you have there.What's going on with the prices?I had to ask 6 or 7 quotations from different places, when making my system until I found someone that didn't try to screw me over.

author: Siwastaja
author_rank: Super Contributor
timestamp: August 19, 2024, 02:45:09 pm
content: Pick panels by cost per kWp. Don't fall into trap that thinking another really-Chinese brand is somehow magically of high quality just because it's more expensive and marketing people make outrageous stories. Also don't fall into trap by buying unnecessarily state-of-the art 0.1%-point higher efficiency panels for significantly more money. Usually you are notthatconstrained in space. You can use the same money to buy 1-2 panels more.Solar panels are ridiculously cheap now. Real cost for a retailer is around 40-50 EUR for a ~400W (or a tad over) panel (so less than 100 NZD). PV panels are so cheap they are often cheaper than e.g. roof materials or melamine board so people are actually using them to build tabletops, shelving or bikesheds or whatever.So it's all about supply chain and markup. You probably should ask quotations for whole installs because professional installers of course get all the benefits of scale. Even if they sell a 100NZD (to them) panel to you for 300NZD, maybe they sell the install work then much cheaper than some competitor who asks less for the panels..? Market mechanisms are often illogical and vary a lot by location; maybe it is most cost effective to buy panels yourself (maybe making a group buy with some neighbors) and then get a contractor to install them with hourly billing, instead of turn-key solution? ... or maybe not.Very likely after 15 years there is no one present to respond to your warranty claims, so by buying the cheapest you have wasted the least amount of money if something goes wrong. But of course, ignore iffy sources like random Alibaba specials or products no one in the industry knows.

author: fastbike
author_rank: Regular Contributor
timestamp: August 19, 2024, 06:15:08 pm
content: Quote from: Siwastaja on August 19, 2024, 02:45:09 pmYes I am ignoring the claimed efficiency of around 22%. We have a great local research agency (NIWA) that actually has loads of data on real world insolation for multiple locations here in New Zealand.It also has a worked example for panel efficiency in the real world. So theLongipanels referenced have an area of 1.95m2and a claimed output of 440W. This is 225W/m2.Given max insolation is 1370W/m2(when perpendicular, clear skies etc), efficiency is 225/1370 =16.4%.The Trina ones will be slightly lower as they are a little longer (same width) but both fit on the roof.You can plug in your lat/long (or address), the tilt of the panel and the bearing from true north (panels face north in the southern hemisphere) and click go and you get a visual depiction of the sun path for 5 selected months along with cumulative hourly insolation. Data for each month on the 21st day can also be downloaded. It's really useful to model what the likely daily output is for each of the 12 months (to help with battery sizing) and annually (to help with payback period calcs).And the roof in question. It faces 14 degrees off north and has a slope of 26 degrees at the front and around 12 degrees at the ridge (it is a curved mono pitch which presents some interesting mounting challenges !)QuoteAgreed. There a quite a few solar installation companies in the market, some with a good history but pricey (makes sense) and then what I would politely call cowboys who are either cutting corners (not good) or trying to undercut the established players so unlikely to be around for warranty service (also not good).I plan on using the model my sister followed a couple of years back when her house was remodelled - her builder and sparky did the work. In my case I will act as the contractor (I built the house 20 years ago) and get a competent sparky to do the electrical/compliance related stuff so it is all certified (required by law and also to get a feedin connection to the grid). Of course prices have fallen heaps in the last two years so time to get moving.

author: nctnico
author_rank: Super Contributor
timestamp: August 19, 2024, 06:36:29 pm
content: I have used quite a few tools to calculate the theoretical power from my solar panel install only to find they are all wrong.

author: Wolfram
author_rank: Frequent Contributor
timestamp: August 19, 2024, 09:50:13 pm
content: Quote from: fastbike on August 19, 2024, 06:15:08 pmThe specified output power is at an insolation of 1000 W/m^2 and 25 C according to the datasheet of the panels. They are not guaranteed to give more power at higher insolation, and temperature impacts efficiency. Do you have any more data on the conditions under which 440 W at 1370 W/m^2 was measured?

author: fastbike
author_rank: Regular Contributor
timestamp: August 20, 2024, 12:10:55 am
content: Quote from: Wolfram on August 19, 2024, 09:50:13 pmData shows that my location/installation rarely sees 1000W/m2at my latitude and tilt/heading.So no problems about higher insolation.The worst case is that my modelling using 16% vs 22% from the manufacturer is conservative.What would be useful is a graph of efficiency at lower insolation levels. The data sheet shows (STC) 440W at 1000W/m2of insolation and (NOCT) 337W at 800W/m2. Is the output vs input normally linear for panels ?Edit; just saw the graph on the Trina panel datasheet showing a output for 200/400/600/800/1000W of insolation. Eyeballing the power output (assuming efficient MPPT) shows a relatively linear correlation between insolation and panel output. I could rerun my figures but the system is economic already so payback just reduces if I'm lucky.

author: Siwastaja
author_rank: Super Contributor
timestamp: August 20, 2024, 05:29:11 am
content: Quote from: nctnico on August 19, 2024, 06:36:29 pmFor me, PVGIS when given correct input parameters seems to be very close to truth, within a few %.

author: ustaad
author_rank: Contributor
timestamp: September 01, 2024, 12:56:14 pm
content: PV prices have dropped to roughly PKR 44/Watt here. That would give you around 112 NZD for a 440W panel. That Longi guy definitely ripping you off