Is it true that the optical design of LED fixtures and lamps makes LED lighting the world’s most energy efficient light source? I did have doubts about it’s energy efficiency when I saw some LED retrofit lamps and fixtures having a lower luminous efficacy compared to some discharge light sources such as some HPS, some fluorescent, some MH, and even LPS. Is the claim about LED lighting being the world’s most energy efficient light source a common reason for a country to ban all non-LED lighting?

I'd say that LPS is the most efficient since the lumen efficacy is higher than most, and that the highest wattage I've seen in LPS is 180 watts.

I'd say that LPS is the most efficient since the lumen efficacy is higher than most, and that the highest wattage I've seen in LPS is 180 watts.

Did you know that there actually were LPS lamps that had wattages above 180w. Such examples of LPS lamps higher than 180w include 200w SLI/H lamps, 200w SOI/H lamps, and the highest wattage of any LPS lamp that I know of is 310w for a SLI/H lamp. Did you know that the first SOX lamps were rated as high as 200w and that the 200w SOX lamp was later rerated to its modern 180w.?

From what I understand, Philips achieved 200 Lm/W with economy LPS, but I also understand figures of 300 Lm/W have been achieved for LED, unfortunately though this was only in a lab, because the cost of making such LEDs is still not economically feasible to be able to go on sale to the consumer?

At some point some scientists developed an LED that was 230% efficient, and it worked by taking ambient heat in and converting it to light. Of course this was on an extremely small scale so it wouldn't have any real-world application, but interesting nonetheless.

https://gizmodo.com/scientists-create-230-percent-efficient-led-bulbs-5890719

You've used very specific metrics. Light implies all of the EM spectrum, and efficiency is not as useful as efficacy.

Antimatter is the only 100% efficient light source I'm aware of.

Limiting to electrically-powered sources, I would guess that's either a magnetron, as 65%+ is the norm. or perhaps a near infrared laser diode, which is comfortably above 50% in higher powers.

Or if you actually meant efficacy, that's almost certainly either going to be LED or laser diode, in any usable power level.

At some point some scientists developed an LED that was 230% efficient, and it worked by taking ambient heat in and converting it to light. Of course this was on an extremely small scale so it wouldn't have any real-world application, but interesting nonetheless.

https://gizmodo.com/scientists-create-230-percent-efficient-led-bulbs-5890719

I'm pretty sure nobody did. It would be violating the 2'nd law of thermodynamics, so a perpetual motion of a 2'nd kind.
So either the results are heavily misinterpreted by the media (writing % instead of lm/W; 230lm/W is about 60% with CRI80 4000K white light, which is pretty standard at low power levels and lower temperatures in lab; not for a real lighting workhorse), or it is another "science breakthrough" type of scam.

Those magical LED efficiency results are gotten in magical conditions like cryogenic temperatures and no ballast waste, and are not applicable to the real world when you add the heat and ballast losses. In one post of this thread I talked about why LEDs barely pass the 100lm/w, basically due to the high sensitive to the temperature, which decreases drastically its efficiency and the thermistor effect makes the things worse to the LED chips and the transistor in the ballast.

Those magical LED efficiency results are gotten in magical conditions like cryogenic temperatures and no ballast waste, and are not applicable to the real world when you add the heat and ballast losses. In one post of this thread I talked about why LEDs barely pass the 100lm/w, basically due to the high sensitive to the temperature, which decreases drastically its efficiency and the thermistor effect makes the things worse to the LED chips and the transistor in the ballast.

Thez are sensitive on temperature, but the development is advancing. The 1OOlm/W was the border 5 years ago, now in the real life condition the efficacy of the LEDs are in the 130..150lm/W (the filament style are higher) range for CRI80 (phosphor blends optimized for highest efficacy with allowed lower CRI gain about 20% on efficacy). Big part comes because of the severe cost reduction happening over the years, allowing to use more of the semiconductor area for the same product cost category, so operate the LEDs at lower current densities, where they reach higher efficacies even without any technical modification. Other gain is in the general advances in thermal management designs, reducing the die operating temperatures. The development is mainly around the semiconductor chip alone (mastering mass productions with thinner wafers, better thermal conduction of the chip carrier design, the use of larger chips for the same power is another place to gain few extra degC). And of course there is higher efficacy of the dies and phosphors alone.
With lab environment cryo cooling and low power it is way above 200lm/W since very long time ago. The real application LEDs are already in the 30..50% energy efficiency ballpark, so by the way becoming better than high power SOX (200lm/W at the 550nm means barely 40% energy efficiency, 150lm/W of a CRI80 4000K white means about 45% energy efficiency)

Ballasts have about 80% efficiency for lower power consumer grade products (the sealed filament retrofits), 95+% for the higher power commercial ballasts (for the flat panels, streetlights,...), that allows the whole systems to be at 120..140lm/W excluding optical losses of the fixtures (those you will have with discharges too), again for CRI80.

Let's add the word "raw" when we talk about lamp efficacy.

As in: highest initial raw lamp efficacy; mean raw lamp efficacies; the most efficient raw light source available today.

Otherwise, most LED systems can easily be regarded as the most efficient lighting "devices" today.

I wonder why average “lighting professionals” say that LED lighting is more energy efficient than low pressure sodium lighting?

Most SOX and other LPS luminaires are highly in-efficient. Companies assume we are unscientific, so they just bundle the words "most efficient" to describe LED lighting "systems" overall.

In reality, “lighting professionals” seem to think differently than we do in many ways. For example, even though some of us collectors have successfully lit up PL-L lamps on magnetic ballasts, many “lighting professionals” will say these lamps only work on electronic ballasts.

Even if a whatever lamp works perfectly in whatever gear was not meant for it "professionals" will not recommend it, because they stick to the code, even if it is technically correct, yet not with the code or manufacturer indications, just like running SOX on fluorescent gears.

The main difference is the liability: Where is not that much important how components work when they work as they are designed, but more important becomes when something does not work as it is supposed to.
Proffessionals don't like to be ruined by astronomic payment or criminal prosecutions when something go wrong.
The thing is, something will always go wrong from time to time. It could be their fault, then showing theygenuinely do evrything known in the trade to prevent those fatal mistakes uses to be enough to avoid criminal prosecution and to let the insurance cover the finances. But that means 100% sticking to the Code.
Or some component could be deffective. Then if e.g. a ballast bursts into flames and burns tze house down because of its manufacturing error yield to a short curcuit, once the ballast is installed and used exactly according to the manufacturers instructions, all the liability goes for the ballast manufacturer.
But if you use a fluorescent ballast to power a SOX lamp, the ballast bursts into flames and burns the house down, the maker may easily clain "Yes, there may have been a defect in our product, but should it be used according to our manual, it will not burst into flames that way". And ballast manufacturer is cleared, so all responsibility goes on the one who decided to use a fluorescent ballast for a SOX.

In case of the fluorescent fixture igniting the house, the ballast maker will get away with just a financial compensation, because they will (assume it is really one off event) show a ton of safety analysis they have done, showing a ton of anticipated possible failure modes (supported by tons of tests) and none of them leading to such disaster, proving they did all according to the best practices to prevent such disasters.
But these analyses loose all their validity once you change the lamp type.
So to be "clean" in a similar way, you would have to do all this safety analysis again, for the use with the SOX. Besides it won't ever pay off (it is a huge and expensive work), you will be lacking many internal information from the ballast maker (e.g. the exact process control, which leads to the list of probable defects or makes other defects impossible), which are essential for that analysis (youhave to make sure you cover all defects that are possible in the process and thet you ignore only those defects, which are really impossible).
Yes you may reference analysis made for the fluorescent use, but then you have to prove it is really valid for your use as well (this is done by retrofit lamp makers - like a "HPS to be used instead of MV" or so).