Comparing 2 7kw systems

System
System Posts: 2,511 admin
in General Solar Power Topics #1
We are planning on installing a grid-tied PV system. We are getting quotes for a 6.93 kw Schuco and a 7+(a bit)kw Sunpower system from 2 different installers. Prices are comparable especially after the large CT rebates. The Sunpower installer claims that Sunpower systems are superior and that the estimated annual system output is higher than the 7854 kwh estimate for the Schuco system. Is this just a saleman talking or is he correct?
· Share on Twitter

Comments

  • marks
    marks Registered Users Posts: 17 ✭
    #2
    Re: Comparing 2 7kw systems

    Here's a link that lists a more realistic expectation for the panels: http://www.consumerenergycenter.org/cgi-bin/eligible_pvmodules.cgi

    You can do some math, and figure out what works best for you.
    · Share on Twitter
  • autoxsteve
    autoxsteve Solar Expert Posts: 114 ✭✭✭✭
    #3
    Re: Comparing 2 7kw systems

    Get some local customer references to talk to from both of the installers.

    I did that and their words tell a LOT....
    · Share on Twitter
  • Roderick
    Roderick Solar Expert Posts: 253 ✭✭
    #4
    Re: Comparing 2 7kw systems

    Maybe you've already made your choice by now, but if you were still looking for a way to determine true output of the system:

    Try this link:

    http://www.consumerenergycenter.org/cgi-bin/eligible_pvmodules.cgi

    That's the California estimate of the realistic output of the panels. Also, there's a page for the efficiency of the inverters - you can find it if you click around there. I think it reasonable to assume that California is relatively impartial in its testing.

    The absolute performance of the system will be based a lot on orientation, temperature, and weather. It's not a very useful exercise to try to predict exactly how much energy you will get in a given year, but it IS worth comparing the relative power output from two different proposed installations. Then you can see not only which system would produce more energy per dollar, but also which installer is more conservative in their bid.
    · Share on Twitter
  • jza80
    jza80 Registered Users Posts: 13 ✭
    #5
    Re: Comparing 2 7kw systems

    I have a 5.5kW Sunpower system, the salesman also talked up how the Sunpower panels would have a higher output than competitors. The system has been online about 4 months, so far the output is exceeding expectations. Also, the sunpower panels are smaller for a given output if that is an issue for you.
    · Share on Twitter
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #6
    Re: Comparing 2 7kw systems

    "I have a 5.5kW Sunpower system, the salesman also talked up how the Sunpower panels would have a higher output than competitors."

    jza80,
    i'm not going to judge the product, but any way that you slice it a 5.5kw pv system is a 5.5kw pv system no matter who makes it. now if he meant for a given area of pv to output more than most, then maybe that would be wording it better.
    · Share on Twitter
  • jza80
    jza80 Registered Users Posts: 13 ✭
    #7
    Re: Comparing 2 7kw systems

    Neil, you make a good point. I need to clarify my post- the system is 5.5kW which is all it can do at best, but supposedly the difference is a bit higher generation during lower light conditions (that is the claim, I don’t know if it is true though).

    When I said that it is working better than expected, the CEC estimated annual output for my system is about 7950 kw-h, it seems that the annual will be somewhat higher if the last 4 months are any indication. I have not been on line for a year so it is too soon to know for sure but it is looking very good to exceed that value, so far

    Also I think the output versus surface area is a bit higher than some panels if you compare the sunpower 205W panel with some other brands. Smaller panel for a given output.
    · Share on Twitter
  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    #8
    Re: Comparing 2 7kw systems

    Sunpower panels are Silcon, nothing special about them at all. The increased efficiency is due to the power conducting traces not being on the front shadowing the panels as most panels are.

    On a cost per watt basis they are dead last for Silicon Panels ( least watts per dollar ), the only benifit is they are marginally smaller, but I have never see a roof that only Sunpower panels would fit in and an Evergreen wouldn't as an example

    CEC is based on a number of things, mostly adjusting for common tempature differences from the STC of 25C. Its a swag, averaged over many years.

    Sunpower is a solid performer, but its not any better than an "A" grade Silicon panel from the dozens of manufactures out there.
    · Share on Twitter
  • Drastyn
    Drastyn Registered Users Posts: 2 ✭
    #9
    Unfortunately many installers " play ” on the fact that Sunpower panels (as Panasonic and Sanyo HIT or others) has more efficiency, so more “powerful”. But efficiency doesn’t mean more kWh/yr. This is not true, or not always, too many variables in the field. Less “noble” panels - sometimes - performs better. If you wanna compare real pv outputs from real pv plants all over the world you can use PVoutput.org or PVcompare.net where you can set your place, inclination and orientation and compare real plants..
    · Share on Twitter

Categories