Thought that I'd pass along this information from a solar installer list that I administer. A user asked if very lower power factor numbers were common when exporting solar power to the utility grid via grid-tie inverter. This response comes from one of the senior technicians at Exceltech Inverter:
"Reactive power is one of the more complex aspects of electric power, and
certainly one of the most misunderstood. It can and does involve inductive
loads (e.g. motors), capacitive loads (e.g. some types of power supplies),
and non-linear loads (e.g. switch-mode power supplies, dimmers, etc.).
You likely know (or should know) "power factor" is the ratio of real power to
reactive power consumed by a load. Grid-tie inverters generate "real" watts,
which are then coupled to the grid. When a reactive load in your home is
consuming power, and you provide real watts to the load from the inverter,
this changes the ratio of real to apparent power consumed by the load as
seen by the utility company.
Dividing real power by apparent power results in a unit-less value between 0
and 1 that describes this ratio.
Let's say a load in your home is consuming 1,200 real watts, and 1,250
apparent watts. This results in a power factor of 1200/1250, which equals
0.96. Pretty darn good.
Next, your grid-tie inverter provides 1,000 real watts back to the utility company,
which in turn is 1,000 real watts that the utility company no longer needs to
provide to the load described above. Thus the net "real" power consumed as
seen by the utility is now 1,200W - 1,000W = 200W.
This means they sell only 200 watts to power your load, but the "apparent"
power aspect is still there.
200 real watts / 1250 apparent watts yields a power factor of 0.160. Terrible by
any power company standards, yet you've removed 1,000 watts from the grid.
This is the value that will be displayed on your meter."
Open-source tools for energy monitoring and analysis. This project uses the GNU General Public Licence