@Eleco_SR304 did not reply anything on how he measures it, but 2X figure hints he may be measuring apparent power as V*A product without any correction to power factor applied.

When I pointing my 365nm LED flashlight to sensitive areas in my skin, I feeling heat. Also: When I use my 160W SBMV lamps in my room at my father home, during the summer, I feels hot and sweat, because of the 365nm mercury line.

Also, UVA light is relatively harmless, and it is UVB and UVC which is considered health risks. Especially the light around 260-270nm which is the most mutagenic. It is sure UVC band, and fortunately these wavelengths are not emitted much by most HID lamps even not UV-blocked.

HID ballasts losses use to be between 5..20%, depends on the exact system.
The simplest, cheapest and most efficent are series chokes, when the arc voltage is close to the half of the mains (for a stable arc the mains should not be lower than twice the arc, but the system needs room for lamp aging).
That is, why the lower power HPS in the US/Canada market and pretty much all HIDs in the "230V" area are designed this way, with 55V arc for 120V HPS, 70..90V for "230V" area HPS, about 100..140V for "230V" MV and MH.

Then for lamps with higher arc voltage in the 120V area you need some form of step up transformer and these have vay more windings, so exhibit higher losses. And because of the more windings, they are heavier and more expensive. But the higher open circuit voltage allows the lamps to be more efficient, so these are the main choice for all but the low wattage HPS in the 120V world.

The more complex ballasts allow also designs with the ability to compensate for wider mains voltage fluctuation, which makes the installation mainly with longer wiring simpler, but it costs some extra losses in the ballast (generally the better the regulation, the higher the losses).

The LPS very difficult lamps to power in an efficient way. Unlikethe high pressure lamps, their anode column voltage drop is high from the first ionization, so if you add the high drop of the cold cathodes just after ignition, the ballast needs to beable to deliver quite significant power into a discharge with voltage drop many times higher than the normal operation (after electrode warmup). That means very high OCV requirement. And that means even on 230V, the ballast needs to be more complicated, so (unless some HF electronic gets involved) more lossy. So much the losses use to be in the 50..100% of the rated lamp power (so the ballast efficiency as low as 70..50%). In the latest years, electronic ignitors able to provide the higher voltage feed for the cold cathode stage operation made possible the LPS to suffice with a simple series choke ballast, then the efficiency became closer to the 70..80% (the LPS atill have rather low arc voltage, so the ballast losses remain higher).
Of course completely HF electronic ballasts are able to boost the voltage for the cold cathode operation using resonance, so retain high efficiency for normal operation, but these came too late, when the LPS technology was already on the way out from the market, so there was no motivation anymkre to invest into their adoption.

Sure every person is different, but feeling hot or sweaty is usually not a measure of UVA exposure. Energy densities are not even near to feel direct thermal effect. UVA causes many phosphors to fluoresce, but so does violet and blue light, and the effect hard to tell from UVA.

The "old mechanical energy meters" actually do exttract the real power correctly, provided they are properly calibrated (the phase shift compensation). Their problems were rather high internal power consumption (few W in a single phase voltage coil) and inability to correctly measure/track low power levels (20W and below), regardless of the power factor/THD, it is just a thing of mechanical friction.

But phase shift won't cause wrong reading, neither high harmonic content. The disc torque is just plain product of eddy current field and the load current field at any instant, so once the voltage coil field is calibrated well (the one responsible to form the eddy currents in the disc), just plain physics makes sure the true power is registered well.

Oh, for the 100w HPS bulb, I had a 150w Ballast fitted to the lantern. 

-100w-400w igniter
-20uF capacitor

FC2 is for 250-400W double ended MH and HPS lamps.
And I've five 70W R7s MH lamps, two in 10000K, one in 7500K and two 14000K. They glowing bright cyan at 365nm UV, but produces lots of UVA based on the fact that they heats me and causing me to sweat if I uses them during the summer.

They don't emit UVC, it is just the arc tube is super-super bright and unpleasant to look at, even at just a glance. It wouldn't be a  great indoor light source unless it is diffused in some way, just so it creates less harsh shadows and is easier on the eyes.

Actually, some very old RX7s/G12/FC2 MH lamps in clear *tubular quartz* do emit some hard UV. The way to tell is to shine some blacklight on the lamp envelope. If it fluoresces bright blue, it is doped, and is UV-block/UV safe.

Lamps with E26-E27 bases are all UV safe anyway.

These are official manufacturers measurements too from Osrams 1986 lighting catalog 😎