A power factor penalty is an extra charge some utilities add to a customer's bill when the site has a low power factor or draws a lot of reactive power. Utilities have to supply both real and reactive power but bill customers only for real power, so penalties recover the cost of the reactive power. The penalty grows with the amount of reactive power supplied. Inductive loads such as motors, transformers, pumps and air conditioners need reactive power, and that pulls the power factor down. Adding PV can make the problem worse. An inverter running at unity power factor reduces the active power taken from the grid, but the reactive power drawn stays the same, so the meter at the grid connection point reads a lower power factor. The penalty can also come from PV output that bypasses the feedback of an automatic power factor correction panel, or from harmonic distortion caused by non-linear loads. Fixes include capacitors installed on the customer side of the meter, sending PV output through the correction feedback, and setting a power factor on the inverters. An external controller can also adjust inverter PF and reactive power over Modbus. Not every utility charges for low power factor. Where the utility installs the capacitors itself, the customer still pays a reactive energy fee.
related_toc1 drafted · lead Power factor
The penalty is charged when the customer's power factor is low.
sec=h209 h=63df79f32c05sec=h1 h=e55db763231esec=h1 h=43c4cc3004dbc2 drafted · lead Reactive power
Utilities bill only real power, so penalties cover the reactive power they supply; penalties scale with that reactive power.
sec=h209 h=63df79f32c05sec=h1 h=e55db763231esec=h1 h=43c4cc3004dbc3 drafted · lead Low meter power factor
With PV feeding at unity power factor, grid active power falls while reactive draw stays the same, so the grid-point meter records a lower power factor and the customer can be penalized.
sec=h1 h=e55db763231ec4 drafted · lead Constant power factor mode
One fix: set the inverter power factor to the plant's no-solar value, with the direction opposite to the plant power factor.
sec=h1 h=e55db763231ereview note: support check: partial - u16 says set inverter PF equal to the no-solar value with opposite direction, but doesn't name constant power factor mode explicitly; core is stated.
c5 drafted · lead Harmonic distortion
Harmonics from non-linear loads lower the true power factor even more.
sec=h1 h=e55db763231eAn external controller can adjust inverter PF and Q setpoints over Modbus as conditions change.
sec=h1 h=e55db763231ec7 drafted · lead Energy meter
The meter at the grid connection point measures power factor; a billing meter can compute an average power factor over the billing period.
sec=h209 h=63df79f32c05sec=h1 h=e55db763231esec=6.1 h=9cf8a5029258review note: support check: partial - Grid-connection-point meter PF is supported (u16) and billing-period average PF by KV2C (u28), but u28 doesn't link to penalties and 'billing meter' framing is loose.