I meant photographic darkrooms.

What matters is the total cost over the fixture life. Ballast cost, plus all the lamps spent there, plus the electricity to run them over the whole time.
And given we are talking about way above 100khours total (even many times that), for anything over few W even bellast that you can get for free becomes way too expensive, unless it also does not lead to the highest efficiency combination.
So for a F40T12 size lamp it gets cheaper to pay for a more expensive ballast upfront than for the extra energy the less efficient lower voltage lamp would consume. So the F40T12 are designed with the 100V arc, dictated mainly to allow at least the 230V market to suffice with a series choke.
Note the modern F32T8 replacement is designed for way higher arc voltage and lower current, because the 230V market went the F36T8 way to stay compatible with the F40 ballast. There the 120V market did not go the same F36T8 way, because the most common ballast on 120V, the RS, won't be able to ignite it, so a special ballast would be needed anyway. And with a special ballast, it was then no reason to stick to the F40's current rating, so the lamp was designed for the maximum efficacy for that size.
On the other hand for an F8T5 tube the power is so low the energy savings would not pay the more expensive ballast off. So these are designed to work with 55V arc and suffice with just a series choke for 120V mains.

F20T12 are on the border, but designing them to share components with the higher volume production F40T12 (so benefit with their lower cost due to production scale) was the argument what tilted it towards the ~60V arc. It also allowed two of these to operate using the same ballast as a single F40T12 in 230V areas.

One of the interesting things that I have known about North American lighting is that they have sold 9 inch 30W circline fluorescent lamps primarily for electronically ballasted fixtures, ceiling fan light kits, and screw in adapters for energy efficiency upgrades throughout the 2000s and early to mid 2010s. I wonder why several North American lighting manufacturers specifically decided to sell 9 inch 30W circline fluorescent lamps for dedicated electronically ballasted fixtures for energy efficiency upgrades instead of sticking to solely developing electronic ballasted 20W, 22W, 32W, and 40W T9 circline fluorescent fixtures and why use a circline fluorescent lamp already popular in Japan primarily intended for preheat fluorescent fixtures and market it almost exclusively for electronic ballast use in North America?

A prime example of one of those 9 inch 30W T9 circline fluorescent lamps is the TCP 32030 circline lamp. Even though it is primarily intended for dedicated electronically ballasted fixtures, ceiling fan light kits, and screw in adapters, they still work fine in Japanese magnetically ballasted preheat fluorescent fixtures.

I just always get a kick out of reading the reviews from buyers saying that they finally found the lamp they needed for their ceiling fan light kit after struggling to find the correct 9 inch 30W circline lamp in stores!!

I have seen 860W AllStart CMH retrofits for 1000W QMH lamps, but that is the biggest I have seen. Well I did see a 1000W CMH lamp, but it had 2 arc tubes in series so it doesn't count lol.

Anyway, is there an actual 1000W CMH lamp? Or maybe something even higher? I did some searches here but didn't come up with anything significant. And if not, why? Does CMH only offer significantly greater efficiencies at smaller wattages?

@xmaslightguy
Yeah those VHO tubes I believe have a much higher pressure gas fill (some say it includes neon as well, not sure) which makes the voltage higher than it normally would be at those currents.

@Medved
Oh of course, efficiency is not the goal here. Obviously the most efficient lamp would be lowest current highest voltage, and this is the polar opposite of that. Efficiency would of course be crud. But control gear would be cheaper, making it more attractive to manufacturers (assuming magnetic ballasts are still popular, which they aren't). Yes this whole thing is relatively pointless.

There is the main question: Why would anyone do that?
The lowe the voltage, the grater percentage of that is the voltage drop associated with the electrodes, which generates heat but not light. So the lower the arc voltage the lower the resulting efficacy of the lamp.
So actually the opposite was happening: Making the lamps so the anode column drops as high voltage as possible, while not hitting some other limit.
One of the limits steering most of tradditional lamp sizes was the ability to operate with just a series choke ballast on the given mains. That is the reasom why you find so many lamps with arc voltage in the 50..60V ballpark (about maximum a 120V mains can support; F20T12, F15T8,...), or 90..120V (maximum for 230V mains (F40T12,...). Also when voltage boost is required, the cheapest and most efficient is when the ballast is doubling the mains as OCV (all windings use the same wire), which also leads to the 90..120V ballpark (and tubes like F40T12).
Another restriction, causing mainly the small lamps to deviate from the optimum above, is the intention to have common ballast for multiple lamp sizes (e.g. the miniature T5 family, where just the F8T5 is at the optimal 65V drop, the 6 and 4W are just designed to share the same ballast).
And the last reason to deviate from the optimum is the intention to make the lamp compatible with existing ballast, but lower the real power to save energy when the technology compensates by higher efficacy, like the F34T12.

So yes, it is possible to modify the lamp designs for lower arc voltage and higher currents, but there is no reason for doing that.

Don't forget there's also the 48" VHO which is 110w/1500ma (my calculations gave 73v on that though)

If your lamp has operating position restrictions, it is especially paramount to run it in its designated operating position such as VBU for base up or HOR for horizontal. If it is  rated for universal burning, it should safely operate in any position, but I recommend even operating universal burn lamps base up for maximum longevity.

The lowest voltage I have seen on a 4ft T12 tube is 71V, and that is from a 63W F48T12HO, presumably due to it's current being doubled. A close second is of course the 79V F34T12 energy saving version of F40T12, and that voltage drop is due to there being some krypton in there. Normal F40T12s are around 101V. So that got me thinking.

- Moving from .43A to .8A results in a ~30% decrease in lamp voltage.
- Moving from pure argon + mercury to a specific mixture of argon + krypton + mercury results in a ~22% decrease in lamp voltage.

What if we do both? Meaning have a lamp that is running at around .8A with a krypton+argon fill. I am sure it doesn't work this way, but if we use those same percentages we get 101*.7=71, 71*(79/101)=55.3V. So A 4ft T12 tube with a drop of ~55V. This is almost certainly low enough to be used with a choke on 120V. And what's more is that 55.3V*.8A=44.24VA, so it's wattage (and hopefully light output) is probably very similar to a normal F40T12, just higher current and lower voltage.

And what's more is that these specs are similar to the 37W F24T12HO (41V@.8A), so there might be compatibility there, no need for dedicated new ballast. If not, there is the possibility of using a 35W HPS choke ballast in a preheat configuration (55V@.83A).

Has anything like this been done before? Meaning two fluorescent lamps of identical physical dimensions and similar wattages that aren't electrically compatible? How possible would this lamp be? This seems like something American Fluorescent would've jumped on with their weird preheat-ish shop lights...

I would make a drawing out of this as usual, but there would probably be nothing visually different about it so that wouldn't be so productive.

This is the lamp, it’s definitely not a shielded arc tube. It’s also new-old stock found in my churches basement after they got rid of their high-bays in favor of LED’s.