Yeah Idk...too bad there isn't a way to measure a lamp's wattage while running, anything over 100% power factor would be a capacitive load

They do make devices called "kil-a-watt" meters that plug into the power between the device that you want to measure wattage of

Uhh I think you're getting electronic and magnetic confused...I don't think there's such a thing as "Ballast Factor" on magnetic ballasts, although cheap LPF ones do underdrive lamps, like those residential-grade "Shoplite" fixtures that run 40w lamps at 25w.
A .8 amp HPF rapid start ballast draws 96 watts (2x40w=80w for the lamps+16w in ballast losses. I'm not sure about those oddball .77 amp Advance ballasts, (which are still considered full power; anything .76 amp and under is considered "energy saver" hence the .76 amp and .73 amp modern ballasts that don't run lamps at full power) but my .77 amp Advance seems just as bright as it's neighboring .8 amp Universal Therm-O-Matic (green/yellow label like yours) and the .8 amp GE Bonusline.
HPF is High Power Factor, and NPF means Normal Power Factor, but many people (including myself) use LPF to differentiate between HPF ballasts. However, most (if not all) NPF/LPF ballasts underdrive lamps.
Anyway, .8 amp and .77 amp magnetic ballasts are full power and run 40w lamps at 40w, while .76 amp and .73 amp ones are energy-saver (and light reducer ) ones.

Actually Universal does list ballast factor for magnetic ballasts Here's a sample spec sheet showing the ballast factor...

Ballast factor is merely a ratio of the current the lamp is driven at over the normal lamp current which is applicable for all ballasts. HPF-LPF magnetic ballasts existed too, IE the Circle-Dot line from GE or more recently the ballasts designed to run 34w lamps IE EPAK 34 (not to be confused with energy saver ballasts)

Power factor is a whole different animal, simply put it's the ratio between the VA drawn and the power drawn by a load. Simplest way to find that is to get a Kill-A-Watt type meter. Generally NPF ballasts have around 0.50 to 0.60 PF and HPF ballasts have 0.9 or higher PF.

NPF ballasts that drove the lamps at >90% output existed in the early days of fluorescent lighting, they only lowered the ballast factor on them recently so they could have a ballast that drove both 30 and 40w lamps. Back in the day 40w and 30w lamps had their own ballast.

Traditional 2 lamp RS ballasts usually drew roughly 750mA to 800mA and preheat usually 800mA to 850mA. Newer energy saver ballasts drew around the 720mA to 750mA mark and the 34w ballasts drew at the 600 to 650mA mark.

To measure the ballast current at the output, get a true RMS clamp on ammeter and clamp it on the output hot lead. This only works on magnetic ballasts as electronic ballasts run the lamps at high frequency and require a oscilloscope to accurately measure the current.

oh wow the energy saver ballasts are 0.73! i thought the energy saver ballasts were 0.77!

Well in that case a 2X F32T8 1.07BF ballast would work to replace 4X F40T12 tubes in the troffers that my grandpa has then. That's great news since 2 lamp electronic ballasts run cooler, less lamps are used, he saves 144.96W (48.32W per fixture), he gains 79 lumens per fixture (ok, well that's not really noticable) and the ballasts only cost $11 each!

BTW Joe, yeah i've noticed that my NPF single lamp universal F40T12 ballast appears to run f20 lamps at full brightness. must be a trigger start ballast in disguise lol.

Yeah that's a good deal i think! I wonder if the inner or outer set would be more effective at light distribution? Usually i see the outer set operating in delamp operations but that could be because it looks slightly better

i think using the outer lamps will keep the light more focusses as the light will reflect off the troffer sides like this /* V *\ whereas with the inner lamps in the light probably shines outward a little more since it doesn't reflect off the sides as much like this / *V* \. Just for the heack of it here's the four lamp version lol: /**V**\

There are three troffers at his shop, all with, I assume, VAL-MISER ballasts. Not the best ballasts, but they're better than the new crappola the companies are spitting out today. the HOs and the slimlines are the ones that probably have vintage ballasts and one F40T12/RS strip that looks to be LBF NPF as the tube is DIM!

So yep, three F40T12 troffers which i'll ask if i can retrofit to T8, a single lamp strip that is (IMO) too dim for it's location that i'll ask to retrofit for more light in that area, and there's an 8ft f40T12 curved basket wrap tandem fixture. the wrap fixture is in a closet and it's practically NEVER used so he may not want to retrofit that one if he wants to retrofit any lights at all. the rest of the lights are all slimline strip lights except for two reflector slimlines and two HO reflector lights.

I'm going to offer to swap out the bathroom light for free so i don't see any reason that he'd refuse. The only bad thing would be if he or i needed to use the bathroom when i'm the middle of swapping the fixtures since there's no windows and there's only one light in there lol. Needless to say i will be bringing a thrid light as a work light. probably my McCann Lighting Bucket Light Mini that i made a few years back. I'll stick my SBMV lamp in it or a 300w incandescent. I don't know where I'd plug it in though...

If he declines from retrofitting the troffers i may ask him if i can simply make the troffers two lamp F40 units so i can have the ballasts. this is probably the first time since the lights were installed that there's been no dead tubes in his lights so two lamps is probably enough light lol.

Yeah, get the preheater!!!
You going to use that A-shape Westy SBMV from Joe M. in your worklight? COOL!

Oh i will! i'm debating whether or not to use the SBMV lamp. I don't want it to get damaged nor do i want to wait for it to restrike in the event the power gets interrupted. I'll probably use my 300W Sylvania incandescent lamp.

EDIT: Oh wait! he has an LOA 2X F40T12 shop lite that was a subsitute for the HO fixture while it was out (he didn't want to spend $15 for a pair of lamps lol, but he did recently and i had relamped it with 110W altos). i can use that as my work light. i'll probably still bring an extension cord with me though since the cord for that is only like 4-5ft long.

I would use the outer lamps since they look better when you only have two lamps fitted. Some troffers here have a extra slot between the inner and outer lamps, that slot is even better. Maybe you could even cut your own slots in the socket bracket.

Yeah i'll probably use the outer lamps. I'll play around with the T12s while they're in there to see what's better but i think the outer will look better like you said. i don't know about the slots. I don't want to go crazy cutting holes in the light either lol.

Wonder if you could get the LOA shoplight too? Even though they are rather cheesy, they are still interesting, unique fixtures from a (now bygone) era...

The cheesy LOA shoplights are rarely seen in my area, my local Walmart sells them but at around $20 per fixture it's out of my experimental fixture budget. I can get a brand new commercial grade fixture at Restore for the same price or less.

Yeah, I'm of a similar mentality...

yeah plus the new ones have that funky electronic ballast that randomly has the EOL protection trip in the cold weather from what ive heard,(i would not ever buy one unless it was freee or real cheap) i think the older ones would be more reliable being magnetic if lamps are changed at EOL

Ehh i'm not too enthusiastic about getting it but yeah it is an older one so I may try. My grandpa has an NOS one from the 80s still in the box with a pair of Philips lamps but the cord is only a few inches long, which in my opinion is POINTLESS!!!!! It's probably one of the first ones though. BTW, can those magnetic LOA ones handle 34W lamps or even T8s? I know they throw a fit when it's under 50F. I think the electronic ones are rated for 32, 34, and 40W lamps.

My local Benny's sells cheesy shoplites for 7-10 dollars but like Aaron said, i wouldn't buy one. At least not for my use lol. I know it could be retrofitted and all but do you really want to waste a good ballast on a crappy fixture? lol

The Designer's Edge makes a decent electronic shoplight that has a pull chain, is all metal, has a 5' cord, and can run F32T8s, F25T12s, F34T132s, and F40T12s. I only see them with T8s though...but they seem to be decent quality, albeit with a cheap electronic instant-start ballast with EOL protection...
You could always put a longer cord on that LOA shoplight...and install modern tubes.

I'd probably just connect an extension cord to it instead.

Yeah, or buy an extension cord, cut it to the desired length, and wire it into the fixture.

I would just leave the extension cord as is and just plug it in to the existing cord if the fixture already has a plug on it, that way the cord can be reused.

i meant that i'd simply plug the short fixture plug into an extension cord so i can have more slack when i need it yet keep the fixture original, as it is NOS.