Ok so did some testing,
Subject:
I bought a brand new Diamond Back Scout, for the sake of testing I left it exactly as it comes from the factory and only swapped the power supply to gauge the effect of the PP on operating temps.
Testing Method:
I would swap the power supply, fly out from the station, make sure all modules were activated, park and let the ship sit for a few minutes to come to neutral. This is the "on" reading.
I would then deactivate every module except the PP and allow the ship to sit until I had 1:00 left on the life support to get the "off" reading and gauge the heat being generated by the PP alone.
All measurements taken with neutral pips (2/2/2) just outside the no-fire zone of Goldstein, Lembava. (on a side note I'm not sure if direct sun effects temperature, if it does, these results are bad as some were taken in sun and some were not)
A4(15.6 MW eff B)
18% on
4% off
B4(14.3 MW eff C)
17% on
3% off
C4(13 MW Eff C)
20% on
3% off
D4(11.7 MW eff D)
23% on
2% off
E4(10.4MW eff F):
26% on
3% off
A3(12mw eff A)
17% on
3% off
B3(11mw eff C)
19% on
2% off
C3(10mw eff C)
19% on
2% off
D3 (9mw eff D)
23% on
4% off
E3(8mw eff F)
27% on
4% off
A2(9.6 MW eff B)
16% on
2% off
B2(8.8mw eff C)
18% on
2% off
C2(8 mw eff C)
18% on
4% off
D2(7.2 MW eff D)
22% on
4% off
E2(too little power to test accurately)