Bruce Richmond wrote:

The point here is that there is no such thing as the grid not being
able to accept the power you have produced. As long as you are
connected you can always force your KW in.

I don't think the issue is whether or not you can force current into the
grid via your 120/208 VAC service connection.

The question is:

a) does your power source need to overcome the instantaneous line
voltage in order to achieve a flow of current (answer: yes, and to the
extent that your power source has the capacity to do so, you raise the
output voltage as high as you can, because if you don't - then you have
excess capacity that is not going to make it out to the grid and hence
you won't gain revenue for the entire potential of your generating
system)

b) by raising the voltage on your local 120/208 grid, can your local
stepdown transformer adjust it's own operation by sensing that higher
voltage and reduce it's own output voltage in an attempt to regulate the
system back down to the desired setpoint? (answer: I don't know -
probably not. The neighborhood stepdown transformers probably weren't
designed to compete with sources of current being connected to their
distribution outputs).

c) So if the voltage on your local 120/208 grid is being raised slightly
because of your PV system and it's desire to push as much current back
into the grid as it can generate, then will this actually reduce the
amount of current that the regional sub-station is sending to your local
step-down transformer? (answer: the substation probably doesn't have a
direct line to your local stepdown transformer, and any alterations it
can make to it's output voltage is probably seen by many step-down
transformers including yours that are all wired to the same circuit. So
in reality it's doubtful that the regional substation would even sense
that your PV system has raised the local grid voltage).

d) So your PV system is raising the local grid voltage, and you're
probably pushing out 40 amps at 120 VAC or 20 amps at 240 VAC on a sunny
summer day. So what is that extra juice doing? Well, it's flowing
through the compressor motors of 10 to 20 of your neighbor's AC units -
whether they need it or not. Because you've raised the local grid
voltage slightly, that translates into a few extra watts (maybe 250
watts for each house that's fed from the same stepdown transformer). So
all the fridge compressors and AC compressor motors, lights - all linear
loads are going to blow away that extra line voltage as heat - instead
of useful work.

Nuf said?