I have two proposals from 2 companies. Cost difference is $500 between the two, so I consider it negligible. I'm hoping a few of the experts here can help me decide which is "better". My electric meter is mounted on my barn, so the solar panels will be near the barn, not the house. My location is Livonia NY 14487. We get a decent amount of snow too. Proposal A is for 6.3kw system, using (20) Vikram 315 watt panels, ground mounted facing perfectly south. The contractor claims this system will produce 8,009 kWh/Year. Proposal B is for a 7.6 kw system, using (22) 345 watt Solar World 345W Mono Solar Panels. The contractor claims 8880 kWh/Year. These panels will be mounted on the roof of my pole barn (4/12 pitch). HOWEVER - the ridge of my barn runs almost perfectly north south (I believe 5 degrees to the E) so, the angle toward the sun is not good. The panels would have to be mounted on the east, west, or both sides. SO - I am not sure which system would produce more energy. Can I trust the contractors estimates? Is one system better than the other from a protection standpoint? Does snow cover pose a problem? I could broom off ground mounts but not roof mounts.

Also, if anyone knows how to break up their posts, let me know. I always hit enter to start new paragraphs but it never stays after I "post". It makes for one long run-on paragraph!!

I don't know the addresses now, but there are web sites with solar calculators that you plug in both vertical angle and orientation for your location and it'll give you comparisons of energy collection. Unless you mount them on articulating mounts that will keep them pointed directly at the sun all day all year you'll have to compromise. I installed water heating panels and opted to orient them as close to E-W as I could and tilted to optimize for October & March sun tracking. Efficiency in the middle of winter isn't as high as it would be if they were more vertical, and summer efficiency is less than optimal. But summer insolence values are so high I felt I could afford to give up summer energy production in favor of winter energy production.

I installed two panels and considered having one point mostly east and the other mostly west, but the overall efficiency wasn't as good as both pointed south. Solar PV panels may be less sensitive to orientation and tilt than water heating panels, but I don't know.

I've done some google searching but I can't seem to find the calculators you mention.

How hard is it to install solar panels? I am building my own home and do home improvements for a living so I am plenty handy. I just have no knowledge of the wiring, and electrical is my "weak link". Are the "kits" that you can purchase online plug and play? Like are the wires simple plug-ins or is the wiring complicated??

This 7.4 kw kit would save me $2700 after tax credits OR I could save $1400 bucks and upgrade to a much larger 10kwh system if I can do it myself.

Google Build it Solar.com. Lots of good information and calculators there.

If you have the land, there's no question that ground mount is the better option. Placing panels on roofs always results in complications, problems and increased expense long term.

Posted By sailawayrb on 02 Apr 2017 03:28 PM
Google Build it Solar.com. Lots of good information and calculators there.

If you have the land, there's no question that ground mount is the better option. Placing panels on roofs always results in complications, problems and increased expense long term.

Could you explain why that is? I would have thought the opposite? And thank you for the website referral I will check that out.

Posted By loghomebuilder on 31 Mar 2017 08:04 PM
Also, if anyone knows how to break up their posts, let me know. I always hit enter to start new paragraphs but it never stays after I "post". It makes for one long run-on paragraph!!

This forum dosn't always convert the commands from your browser(return) into HTML commands that this forum engine operates on. The HTML command for a return or break is
Replace the word space with a single space between br and /. I cannot actually type it as the forum will simply read the command and insert a break.

Also, is it correct that the distance from the solar panel to the meter should be kept to a minimum? If I do ground mounts, the nearest point of the rack will have to be almost 100 feet from the panel. or more.

Ground vs roof, ground would be better IMO.
1. Can have comromised efficiency due to existing roofline orientation.
2. Any issues with roof, well you got all that solar hardwre in the way to even get to the repair.
3. Not done carefully, that solar hardware could be the cause of the roof issues mentioned in #2 above.
4. Any repair on a roof mount will involve a ladder and extra hazard.
5. Panels covered with snow don't make much power and are hard to clear.
6. Dirty panels make less power and are difficult to clean.
7. Hot panels are less efficient, roofs get real hot.
8. Although rare, controller or wiring issues have caused panels to cook-off(google solar panel fire). Although not typically catistrophic to the house, not a great place for a fire either...

Ground mount installations allow optimization of orientation and avoid/mitigate all the aforementioned pitfalls. You can also more easilly add panel tracking to increase output significantly. Easy cleaning and maintenance, using nothing more than a stepladder. Perhaps less wiring do to more desireable location to home power feed like you mentioned near your pole barn. Also simpler wire routing(buried conduit) instead of passing this wiring thru perhaps floor, ceiling and roof structure...

Posted By loghomebuilder on 03 Apr 2017 11:52 PM
Also, is it correct that the distance from the solar panel to the meter should be kept to a minimum? If I do ground mounts, the nearest point of the rack will have to be almost 100 feet from the panel. or more.

It depends on where your inverter is located. At 120VAC you can move 1200W with a cable capable of carrying 10A. At 12V, you would need a cable capable of carrying 100A to move that same 1200W which would have serious isues with loss over distance. If the inverter is near the panels 100' is not ideal, but is probably doable.

. That is why I like the micro-inverter concept. Each panel has it's own microinverter that syncs with the grid and backfeeds. Since each panel is making synced AC, you can run eight 250W panels on a standard 20A domestic wiring circuit using local/common house wiring cable, hardware and installation standards/techniques.

Here are some good calculators, all different presentation of results.

http://pvwatts.nrel.gov/pvwatts.php

http://pveducation.org/pvcdrom/calculation-of-solar-insolation

https://www.wunderground.com/calculators/solar.html

dmaceld - thanks for posting those links - very helpful. They actually show the roof mount system producing more power, even with lower efficiency. The roof is exposed fastener metal, over an unfinished barn, so I am not too worried about problems there.

Ronmar - My pole barn is 80 foot long, so in a roof mount setup, the panels couldn't be more than 100 feet away. Forgive my lack of knowledge regarding the science behind electricity, but would a 120 volt solar output, as you described above, be "normal?"

Another question - I have a wood stove in the barn, not used often, but I take the chill off in the winter with it when I'm working out there. Is there anything I should be careful of with that?

Here is the kit I'm considering. Seems to be the best price I've found online. Its the 10 kw best value kit if this link doesn't work.

https://tandem-solar-systems.com/cart/

Posted By loghomebuilder on 05 Apr 2017 12:42 AM
Ronmar - My pole barn is 80 foot long, so in a roof mount setup, the panels couldn't be more than 100 feet away. Forgive my lack of knowledge regarding the science behind electricity, but would a 120 volt solar output, as you described above, be "normal?"

. I was really only using 120V as an example. A typical panel outputs around 30 VDC unloaded. This voltage drops as a load is applied by the inverter converting it to AC. Think of it as a solar battery. You wire these panels in series to increase the DC voltage output within the range of your inverter. You then wire these series groups of panels in parallel to increase the current output to the inverter at that voltage. Running low voltage DC at high current typically takes very large wire and has resistance losses. Running high voltage DC can use smaller wire, but has other risks. You ideally want the inverter as close to the panels as is practical to cut down on the large gauge expensive wire.

. The inverter will typically output 120VAC or 120/240VAC, the same as is available in a typical domestic power service panel.

Posted By loghomebuilder on 05 Apr 2017 12:44 AM
Here is the kit I'm considering. Seems to be the best price I've found online. Its the 10 kw best value kit if this link doesn't work.

https://tandem-solar-systems.com/cart/

And that system solves the inverter location issue as it uses a single microinverter for every 2 panels, so all the wiring from the panels to the service connection will be the same as the rest of the wiring in your house/barn. The microinverters make it a lot easier... The max distance between the electrical service point and the panels/microinverters should be a spec the microinverter manufacturer can provide...