My Nissan Leaf Forum

Hi Bicster,

You're in Houston, I see. Was wondering if you went to the "Solar Panels in Houston" program at the city's Code Enforcement Building last week. My GF and I were there, found it reasonably informative. I was most encouraged by the enthusiasm both company speakers (from Standard Renewable and Alternative Power Solutions) had for installing micro inverters.

I didn't know about that. I'm sorry I missed it!

I am more and more convinced that Microinverters are the way to go, you can start with a small # of panels and keep expanding it, and the wiring is very simple, and no High Voltage Dc wiring needed. up to 14-15 panels per 15A 2-pole circuit as I remember it... much simpler to wire, simpler to expand, and also no "single" point of failure with 1 or 2 main inverters.. also has benifets if you have some shading, as you only lose output on the affected panel(s) not the entire string.

Well, it was way overbooked, with twice as many RSVPs as available seats. So maybe they'll have another one. Some other info I came away with: expect the cost of an installed residential system to be about $5.50 per watt; and there's a rumor that Centerpoint will start some sort of financial incentive in 2011 for installing solar panels. Anyway, they have a variety of dispalys in their lobby promoting green construction / renovation (inclding solar), plus you can ask a gentleman there for free advice and guidance. If you ever gat the chance, I do recommend paying them a visit.

But the way our utility rebate works, you only get a rebate on an entire system as installed. You get nothing for add-on's to an existing system.

BTW, what are the thoughts of Microinverters vs. a regular inverter, particularly when it comes to cost, reliability, and adding complexity to the system? One of the companies responding seems pretty keen on selling me those over a standard inverter.

What efficiency do the Micro-verters have?

One big high-quality 7kW inverter from SMA SunnyBoy, vs 33 MVs, which cost more.

I went with the one world-reputation SB inverted, but the MVs, from what I could see two years ago, did not have much of a track record to evaluate.

Now, the MVs might be much better, but ... my 7kW inverter is still working fine after 17 months.

Cost: Regular central inverter is cheaper. Enphase micro-inverters cost about $1/watt, central inverters can cut that cost in half.

Reliability: Enphase has a standard 15-year warranty - others have a 10-year warranty standard (though I note that SMA will let you pay extra for an extended warranty). Some say that because now you have more inverters, the chance of failure is higher. Some don't like the fact that electrolytic caps are used since they will eventually fail. Enphase is obviously comfortable enough to offer a 15-year warranty and has a number of white-papers bragging about MTBF. Benefit of a micro-inverter failure is that a failure won't bring down your entire array, just the one panel which in theory, combined with the high MTBF should result in higher overall uptime.

Complexity: It is slightly more labor intensive to install the Enphase micro-inverters as it is an additional component you have to rack up.

As mitch672 said, benefits are no high voltage DC wiring which can be more prone to issues than lower voltage AC wiring, if you have any shading issues, the micro-inverters will maximize output and there is no single point of failure with the inverters. Enphase also has "twin-pack" inverters which ties two inverters into one package which reduces labor cost (half as many inverters to install) and lets you string a few more panels on per string (up to 20 vs 15).

Having self-installed my own PV system with micro-inverters I would not hesitate to use them again.

I hear that the next generation of inverters that Enphase are working on will further reduce the size (size of a cell-phone, ideally integrated into the panel to avoid additional labor install costs), cost (to be more competitive with standard inverters) and eliminate the electrolytic caps that many worry about failing, but who knows when that will be ready for production as all we know about the next generation are rumors!

how does %95 efficient grab ya?

Efficiency
Peak Inverter Efficiency: 95.5%
CEC Weighted Efficiency: 95.0%
Nominal MPP Tracking: 99.6%

http://www.affordable-solar.com/enphase ... 40-s01.htm

Costs maybe %15-%20 more, but has built in redundancy, and the system can be expanded as well.
I will never use a single inverter, not with this technology available...

I sorted the issue out with the company who visited me on Saturday. Of course it was their pre-screener who didn't know his arse from his elbow.

One interesting nugget to come out of this particular visit....the guy said that after the beginning of next year, the utilities are going to be paying for all excess generation, not just generation that would zero out your yearly utility bill. This is the first I've heard of this. Does anyone here know anything more about it?

Edit: Looks like this is it....AB920:

http://www.sce.com/customergeneration/nem-ab920.htm

That's about it. The rate that will be paid for excess generation has not yet been set.