Expandable system?

[electricblue]

Is it possible to put in a large inverter hooked to a few panels and slowly expand the system?

[billvon]

Is it possible to put in a large inverter hooked to a few panels and slowly expand the system?

(I'm going to assume you mean grid tied inverters here)

To some degree - yes. With modern high voltage inverters, the limitation on the smallest system you can do is its minimum operating voltage; you need a string long enough to produce the minimum voltage the inverter needs to operate, which is often in the range of 200-250 volts. Once you have that you can expand in two directions:

1) Add more series panels up to the voltage limits of the inverter. Most inverters have an absolute max limit of 600V that must never be exceeded, and an MPPT max of somewhat less (around 480 volts.) As an example here you could start with 10 Kyocera KD220's on a Sunny Boy 3800 and then expand to 16 panels (depending on climate.)

2) Add more parallel strings. Each string must have the same number of panels/same type of panels as the original string. So if your original string has 10 panels you have to add 10 more at a time. If you do this with more than 2 strings you have to have an additional fuse per string.

Warnings - mixing and matching panel types doesn't work well, although if you are careful the additional lost power isn't too significant. That means you might be constrained to get the same (or very similar) panels to expand. Also, buying a 3800 watt inverter for a 600 watt system is pretty lossy - your tare losses will reduce your efficiency somewhat.

[Elkhornsun]

Actually depending upon the inverter each of the strings need not be identical. If an inverter can take multiple strings each string can have its own set of panels and the strings do not need to be the same. This is different than having two strings of panels in series that are then combined to create a single parallel feed. You don't need only a higher capacity inverter but one that is designed to work with multiple strings as inputs.

[raydias]

Take a look at the Power-One line of inverters. They have 2 or more MPPT inputs for different strings or even different orientated strings like west and est etc. They have a lower start up voltage that can be set to 130v I believe.

[wetpwet]

I hope the OP don't mind me posting here but my question is somewhat similar.

My monthly consumption at my home office is around 900KW or about 30KW a day, 12 hour operation. There is a time in a day that all of my equipments are on and its about 12KW total load that runs about 3 to 4 hours everyday.

I'm only planning to get about 1KW grid-tie system with an option to expand in the future. In my computation in a 6 hour day light (shortest day) I'll be needing about 6.67KW system (30KW/day / 6 hour/day / .75 efficiency) or probably less since we do not have winter and I have no shading problem to be off grid.

What inverter should I get? the 12KW or the 7KW? I was reading an article about solar panels and it says that inverters can be stacked. Does this mean I can get the 1KW inverter and later I can just expand another 1KW system?

BTW does this mean if I get a 1KW system I'll be saving 15% (1KW * 6 hours/day *.75 eff *100% / 30KW/day ) assuming there are no rainy / cloudy days?

[Wy_White_Wolf]

Is it possible to put in a large inverter hooked to a few panels and slowly expand the system?

IMO - You would be better off to use micro inverters. An enphase system would allow you to start with only 1 panel and you could expand to 14 (I think) before you would need to add another circuit. Downside, going either way, would be the permit costs of every time you wanted to add another panel(s). Government always wants it's cut. You may also be required to sign another agreement with the PoCo every time you expand.

WWW