Hello from south central VA

[Billaban]

Greetings,

Definite newbie here. We sold everything in the city and moved to the country. Lots of land and good exposure to the southern sky for solar power adventures. I don't have an electrical background but I am an engineer.

Looking at a couple projects to start:

1. Solar powered deer fence for gardens and orchards. A couple acres or so to start. Most of the fence controllers I have seen so far appear to be designed for plugging into grid 110V AC power. Prefer to do an autonomous configuration with battery storage. Need to get back to YouTube and find some sample configurations that I found last year.

2. Looking at grid tie inverter kits just to see what is available. What I found on Amazon (yes, I'm sure there are better sources) seems like a bad investment. Is the following math correct?


Unit cost $800. After US Fed 30% tax break call it $560.

Power company lists our KwH rate at just over $0.12.

Advertisement w/ unit described 240 Watt panel and estimates 400kWh/yr.

So: 400 * 0.12 = $48/yr of power generated (and presumably used) and therefore the ROI on the kit is $560 / $48/yr = 11.6 years ... assuming static rate @ 12 cents / KWh and zero maintenance.

Is this correct? Over 11 years to break even? I'm hoping that somehow this math is incorrect or much cheaper configurations are available. I understand the draw to solar power and want to jump on the bandwagon but this long of an ROI seems like a bad idea.

All suggestions and comments welcome. Thanks.

[SunEagle]

Most ROI's for a grid tie system take over 10 years if your power cost from the POCO is less than $0.20/kWh. Places like California or Hawaii where the rates are much higher will shorten the time period to less than ten years.

If you add batteries into the formula you can forget any payback. A solar/battery system will cost 5 to 10 times to generate the same amount of kWh that you can purchase from your POCO and your batteries last maybe 5 years which is another big investment to add to the total cost.

Maybe a small system for your fence might be cost effective but if you only pay $0.12/kWh it will be cheaper to run 110v power to the fence controller even if it is hundreds of feet from the house.

Oh last tip. I do not know what grid tie system you saw on Amazon but any grid tie inverter that "plugs into" a house outlet is not legal in the US and worse have caused fires due to their low quality.

[Billaban]

Thanks for the input. I will rethink my projects.

Listing from Amazon that is supposedly UL approved: http://www.amazon.com/dp/B00MU09DL0/...=IQCLM5GPXYV7C

[SunEagle]

You are correct that system can be considered UL approved but they do not tell you that the receptacle that you plug into must be connected to a dedicated circuit breaker in the house panel.

Also you will still need to work with your POCO to allow you to "generate" power back onto their grid. The issue is that most POCO's will not recognize that system as meeting their requirements and not give you the permission to use it.

[gmanInPA]

Greetings,

...
1. Solar powered deer fence for gardens and orchards. A couple acres or so to start. Most of the fence controllers I have seen so far appear to be designed for plugging into grid 110V AC power. Prefer to do an autonomous configuration with battery storage. Need to get back to YouTube and find some sample configurations that I found last year...

WelcomeBillaban - I have three such systems and they're worthwhile if the cost to run power to those fences would otherwise be impossible or prohibitive. A good energizer capable of deterring a large animal can be purchased for ~$350-$550. That is > 5x the cost of a 110v grid-powered unit. Nevertheless, property owners with acreage are not likely interested in running power everywhere they may want a fence. Check our Premeir1Supplies (google) - see their PRS 50 or PRS 100 energizers . They have excellent products and services. These fence energizes can usually power miles of traditional electrified fencing, so a few acres should be very doable.

[inetdog]

You are correct that system can be considered UL approved but they do not tell you that the receptacle that you plug into must be connected to a dedicated circuit breaker in the house panel.

Also you will still need to work with your POCO to allow you to "generate" power back onto their grid. The issue is that most POCO's will not recognize that system as meeting their requirements and not give you the permission to use it.

IMHO even the blanket claim of UL approval is dubious.

...We will send you the specification on solar panel, grid tie inevrter [sic] with UL mark, an electrical line diagram....

The microinverter is UL listed and that listing includes attachment to an appropriate AC trunk cable which is specific to that brand. From there you "wire it in accordance with local electrical codes". The only sure AHJ approval will be for hard wiring between the trunk cable and a PV disconnect.
There has been one other system that advertised plug-and-play and was accepted by most if not all AHJs. That unit required a dedicated non-standard receptacle which matched the non-standard plug on their output cord, and that receptacle had to be installed for the purpose by a licensed electrician. In effect it ends up being a hard wired GTI which happens to have a proprietary cord and receptacle in the middle of the hard wired path.
The dedicated circuit will have to meet all NEC requirements for an inverter output circuit, including the 120% rule on panels that it passes through.

Nevertheless, it beats unlisted plug-and-pray ripoffs.

PS: And one more point: That flexible rubber cord (Type SO or similar) running across the lawn in the photo is an absolute cause for rejection and an NEC violation. Not to mention unsafe.