Small - very small... Grid Tied System

System

What's the smallest grid-tied system I can install? What is the approximate cost of such a system? I'm wondering if I can setup a small system for a few thousand dollars and expand it as money permits.

TIA,
tsp

BB.

Re: Small - very small... Grid Tied System

Grid Tie systems pretty much means that you will have to involve your local building/planning/inspection department(s), your local utility, and a licensed electrician/solar installer (and perhaps the state--if you get state rebates)...

Installing a small system and adding to it--technically--means that most/all of these people need to be involved again each time you add to your system (or you have to "approve" the "maximum" system and add too it).

Around here (SF Bay Area), it seems to cost about $10 per watt (CEC rated, ~85% of the solar panel nameplate rating)--or --installed, permitted, etc... (2 years ago, 3kW system for my home).

Rough Costs:
$5.00 / watt for solar panels
$0.50-$1.00 / watt for inverter
~$4.00 / watt for mounts, permits, turnkey install, etc...

Smaller inverters run around 2,000-3,000 watts each. You can probably find something smaller, and there are larger--plus you can parallel them (as long as your electrical service has the capacity).

You can, of course, save money (shop around for solar panels, get inverters off of Ebay, do much of your own work, etc.). It is not that difficult... However, if this is your first one, it would not hurt to get the help (or hire out) your first install.

Also, not all utilities allow grid tied inverters, especially the co-ops. Also, not all grid-tie rate plans are equal (some are 1 year net metering and others are 1 month, some offer/require Time of Use rate plans, some offer to pay "retail" for your power and others only wholesale).

Questions?

-Bill

I should add, about the smallest Grid Tie inverters I have noticed are around 1,000-1,500 watt units.

And the least amount of solar panels you probably want to connect would be in the 500 watt range--below that, your inverter losses start becoming pretty significant (using a large percentage of your solar power just to "turn on" inverter before it supplies the first watt of electricity to your home).


Try this solar power calculator... Seems to work pretty well in "predicting" my system results.

-BB

Roderick

Re: Small - very small... Grid Tied System

SMA has a SB700U 700-watt grid tied inverter, but it costs like $1500 to $2000. For a few dollars more, you can get a much larger inverter.

After that, figure $4-5 per watt for panels.

So for a 500-watt grid-tied system, I would think the cost would be around $4000, assuming you do all the work yourself for free.

This must not be a cost-effective thing to do; I don't hear of people commonly setting up so small for grid-tied.

Expandability would be another issue, and not free. You could not start with too large an inverter, because the inverter would be running in the really inefficient part of its curve, or else might not start at all. If you had the 700-watt inverter with 500 watts of panels, you could add maybe 300 watts of panels later, but beyond that, would have to trade up to a different inverter. Check out the used market to see if people are selling their old SB700U's - that would give you an idea of what you could get for one.

SolarJohn

Re: Small - very small... Grid Tied System

tsp,

because my budget was small, I started with an off-grid system. I'll probably switch to grid-tied once I have enough panels to make it worthwhile. I didn't want to wait until I saved up enough money for a good-size grid-tied system, and I have no regrets starting small. I can probably sell my 1100 watt inverter on ebay when I'm ready to go grid-tied, or I'll just keep it in case I ever want to use it again. I'm happy that I have a system NOW, rather than wishing for one. It has really come in handy durring a couple of power outages we've had, and it's a great learning tool.

John
http://solarjohn.blogspot.com

nigtomdaw

Re: Small - very small... Grid Tied System

Im not knowledgable on grid tied, but Solar John makes a valid point and if outages are an issue then you have additional benefit. I live off grid and use a Xantrx SW3024E inverter charger but this also has the ability to sell excess power to the grid with the optional GTI Grid Tied Interface approx $450 . I know the SW is coming to its end of production soon,(very reliable 10 +yr product run)* but a 4 kw unit can be bought for less than $2000 new. A small battery bank and spend the rest on panels and you can upgrade PVs as money permits. Selling your used SW in the future when you decide to go completely grid tied should see a high return on your investment s/h SW regularly sell for $1500 + on ebay . Or buy s/h to start with. If I was going primarily grid tie but had grid failure outage issues I would want some form of off grid protection in my system from day one !

System2

Re: Small - very small... Grid Tied System

Concerning small grid tie system:

Presently have a battery based system: Right now 2 - 2 125 Watt Kyocera (17.4 V/7.2Amp) and 2- 85 Watt Shell (Now Solar World- 17.2 V/4.95 Amp) system to 4 USED Data Safe HR 500 sealed VLRA (originally 135 amp hr) batteries from a telephone switchng system.

I try to keep the batteries no less than 75-80% charged, so often when the sun is shining and the batteries are full, I am not taking full advantage of power available.

I have 2 other Kyocera 85 watt panels (17.4V/5 amp) panels that could also be installed on our roof.

Would the Sunny Boy 700 work with 590 watts worth of panels of very slightly different voltages? ( 17.2-17.4 volts?) Not sure if it is a cost effective move but starting to plan ahead.

Thanks in advance for the help and expertise. MJBY1

Solar Guppy

Re: Small - very small... Grid Tied System

No,

All SMA products are High Voltage String inverters ... I beleive the SB700 needs 120 VDC minimum