to grid or not to grid

Earnest Tilley
Earnest Tilley Solar Expert Posts: 56 ✭✭✭✭
i have 8 85 watt 12v panels and i was wondering if i should grid tie them or not is it worth it. I do not have a grid tie inverter and would have to purchase one.


  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: to grid or not to grid

    Not worth trying. You've only got 680 Watts there, which would be a Sunny Boy 700u. The permitting process is basically the same for 200 Watts on a microinverter or 20,000 Watts on central units. Doing it without the right process and using those El Cheapo GT inverters that are hyped on sleazy web sites is not recommended by anyone who actually knows what they're talking about.

    As a rule, off-grid goal is to reduce loads as much as possible and make a very minimal system whereas grid-tie you want to at least offset the household consumption and maybe have some to sell back to the grid. Considering its pretty much the same operation for small GT as for large, going as large as you can afford makes more sense.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,501 admin
    Re: to grid or not to grid

    You have to check with your utility, their rate structure, your power usage, and the local building department and figure out:
    1. What will the fees (utility, building department) be... (may be variable depending on cost of project).
    2. Does your utility support Net Metering? What type (monthly, yearly?). Rates (turn meter backwards, pay you wholesale cost of power)? Is solar power billed differently than your power today (in California, many utilities have to charge Time of Use billing--Summer afternoons/evening power can be very expensive if you use A/C, cook, etc... and cannot shift power usage to different time of day).
    3. How much power do you use? With my utility, if you don't use much power (less than 300 kWH per month), I pay around $0.13 per kWH flat rate. If I use a lot of power (A/C, water pumping, etc.), it can be as high as $0.30 to $0.50 per kWH for energy usage over ~1,000 kWH per month.
    4. Are your panels UL Listed and rated at 600 Volts (series voltage rating)? Many older/smaller panels are not UL Listed and/or may only be rated to ~70 VDC (for battery systems).

    In my area, it appears these day that vendors are looking for 5-10kW GT installations--Their ads appear to not even want to tackle a smaller installation (mine is a 7 year old 3.5 kW installation and supplies way more power than my home needs, on a cost adjusted basis. ~4,800 kWH per year).

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Earnest Tilley
    Earnest Tilley Solar Expert Posts: 56 ✭✭✭✭
    Re: to grid or not to grid

    #1 fees?
    #2 the utility comapny comes out and puts in a meter after supplying info on setup information.
    #3 right around 630kw a month at .09 a kw
    #4 Yes my panels are ul, iec, csa, ce, and tuv
    they require a 10 year contract and my system has to be inspected by a electrition. they pay .12 cents over comercial rates. the system also has to be insured which i have no idea how much that will cost. they also require my system to be able to produce a minimum of 500w and a max of 20kw. Im realy not doing anything with my system accept running a ac and my treatment plant pump which works well never drawing over 1.4kw at any given time.