Hi,
I have one of the Enphase systems. I'm coming up on the one year anniversary -- no problems.
Its described in excruciating detail here:
http://www.builditsolar.com/Projects/PV/EnphasePV/Main.htmGuy Marsden has a detailed description of his Enphase system here:
http://www.arttec.net/SolarPower/index.htmI did all the work myself, and it was a very straight forward system to install. Found the Enphase people to be very cooperative.
I agree with the comment that there should not be a lot of difference in wire size between a grid tie system with strings of PV panels hooked to the inverter vs the Enphase system -- the voltages are of the same order, so the wire sizes should be about the same.
Also agree with the ease of adding to an Enphase type system. Its very easy. You don't have to worry about getting a new big inverter, and the PV panels can be different. WholesaleSolar.com actually has a demo Enphase system in which every panel is a different size and brand!
Also agree that you are more limited on the panels you can use with the Enphase system -- that said, their list of approved PV modules is huge. One notable brand that does not make the list is Evergreen.
When you say you don't have any shading issues -- this is something to think about very carefully. Shading can be very subtle. A roof vent or a fence post you did not think about can cause some shading problems, and the Enphase inverters will handle this better. I don't mean to make this a big deal, and its not that the big inverters fall apart with a little shading, but its something to carefully consider.
http://www.builditsolar.com/Projects/PV/EnphasePV/Shading.htmThe online monitoring that Enphase offers is not required. The EMU unit that goes with each Enphase system provides simple monitoring on its front panel. Basically, it gives current power out, and the historic total output. But, the EMU unit also generates some simple web page reports that you can easily look at from your local computer. The local, EMU generated reports are free, and they do provide health reports and power out reports for each PV panel -- something not reported on big string inverters.
I ran my systems for several months with just the local reporting, and its OK. In the end I signed up for the Enphase online reporting system. This is my system:
http://www.builditsolar.com/Projects/PV/EnphasePV/RealTime.htmI have to say that while they do charge a fee for it, its pretty nice to have.
They keep track of any developing problems right down the the individual inverters, and send you an email if anything needs attention. I'm the kind of lazy person where this kind of reminder is helpful
One piece of advise on the design of an Enphase system. I would pick a PV panel that has a nameplate wattage that is somewhat over the inverter rating. In my case, I'm using 215 watt panels on the 190 watt inverter. I think this is close to the sweet spot. If you go higher in wattage and have a good sun location and the panels are well ventilated, then there may be times when the inverter has to limit the PV panel to the inverter max output. If you go with smaller PV panels, then you are paying for more inverter power than you need for the panel. I guess this is a small point, but I tend to get carried away on these kinds of issues
Enphase just came out with a new dual panel micro inverter that controls a pair of panels rather than just one panel. Don't know what the pricing is like.
Overall, I think that either type of system is fine -- especially if shading and later expansion are not issues for you.
Gary