Geeting more AC outta' DC

quid_nonquid_non Solar Expert Posts: 48
Micro inverters - that's the ticket!


  • n3qikn3qik Solar Expert Posts: 741 ✭✭
    Re: Geeting more AC outta' DC

    They are good if you want to start small and grow, but you will pay more per watt compared to a 2-5KW installed system.
  • RoderickRoderick Solar Expert Posts: 253 ✭✭
    Re: Geeting more AC outta' DC

    There's a big caveat. The microinverters only extract more energy from a non-optimal installation. The idea is that if one panel is shaded, the rest of the array still produces full output, and you still get what you can from that one panel. This would only help if someone was forced to install in such a location. Anyone else would just put the array in a location that's sunny all day.

    Also the efficiency of the small inverters is something like 93-94%, I think. Not bad, but you can do better with one big inverter.

    One thing that I do like is, how else can someone start out with a 200-watt grid-tied system?
  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Geeting more AC outta' DC

    They've been discussed on this forum before.

    I like the idea actually. Converting to AC as close as possible to the PV panels sounds good to me.

    Of course, you also get either lots of redundancy with these things, or lots of points of failure - depending on whether your glass is half empty or half full.

    There is efficiency to consider as well, and if you have batteries then you have to use an AC-DC charger rather than a DC-DC "solar" type charge controller.

    I wouldn't be interested AT ALL in having every one of "my" micro inverters reporting back to Enphase's servers. If I could set them up to report to MY server then that would be a feature I'd like - but if I have to login to their server to control my devices...well screw that.

    (If I was Enphase though, and I had the capability to monitor and control everyone's solar panels...well it wouldn't be any big deal to write a little interface code that would allow the utility company to access that control system - and SELL them that access. They utility could just tout is as another benefit of "smart metering" technology.)
  • BB.BB. Super Moderators, Administrators Posts: 32,027 admin
    Re: Geeting more AC outta' DC

    In California--it is mandatory for all solar GT system over 50kW (PBI) that they must report back to the utility/state to get the state rebates.

    Small systems, I believe that this is an optional requirement.
    The California Solar Initiative pays solar consumers their incentive either all-at-once for smaller systems, or over the course of five years, for larger systems. The program's two incentive payment types are:
    • Expected Performance-Based Buy-Down, or EPBB:
      In 2008-9, systems smaller than 50kW in capacity can receive a one-time, up-front incentive based on expected performance, and calculated by equipment ratings and installation factors (geographic location, tilt and shading). EPBB payments are provided on a $ per watt basis. EPBB is available for systems under 30 KW after 2010. Systems eligible for EPBB can choose to opt-in to the PBI system described below.
    • Performance Based Incentive, or PBI:
      As of January 1, 2008, all systems over 50 kW must take the PBI, and by 2010 all system over 30 kW must be on PBI. Any sized system can elect to take PBI. The PBI pays out an incentive, based on actual kWh production, over a period of five years. PBI payments are provided on a $ per kilowatt-hour basis.

    Roughly, a $2.50 Rebate (small systems) is equivalent to a $0.40 per kWhr payment (for five years of production).

    The current incentive status is around step 4/5 at this time ($0.26 per kWhr / $1.50 per watt rebate)...
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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