The peak efficacy achieved by commercially available LPS lamps is 183lm/W for the lamp itself.  However LPS control gear is hugely inefficient, wasting around 15% of input power, so the real system efficacy is far less than the lamp figures alone would imply.  Due to the large source size the optical efficiency is also poor - as little as half the luminous flux is directed on the intended area for typical luminaires.  The whole system is therefore comparable to HPS lamps with ca. 100-120lm/W.

The peak efficacy achieved by commercially available white LEDs, with CRI>80, when hot and driven at reasonable currents vs 25C datasheet conditions, is around 200lm/W.  Moreover LED drivers are much more efficient, in higher powers regularly exceeding 95% efficiency.  Optical control is outstanding and the light output ratio from good fixtures can approach 90%.  Therefore the complete system far outstrips the performance of LPS.

LPS would still be a good contender if more electronic ballasts had been developed for these and if you just needed an uncontrolled flood of light in all directions, but since the vast majority of fixtures require the light to directed in a particular distribution, it’s actually one of the least efficient systems.  Hence why the development of LPS fixtures and systems was stopped around the end of the 1980s.

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?

Nope

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?

The Answer is "NO". The main light source that is actually efficient is LPS and the manufactures are stopping to make LPS bulbs as it's easier to make "LEDs". They don't actually car if a light source is efficient but if it's easy to make.

And also, SOX, which is basically an LPS bulb, can have 160lm to 180lm per 1 watt where as my Granddad's LED Streetlights uses 100lm per 1 watt  So what's more efficient?

First when comparing bare light sources, LEDs are already in the 150..200 lm/W range at normal operating conditions (so no hypothetical supercooled lab research figures). Yes, it won't be 1800K or 99CRI, but that is not met by the SOX either


But practical system efficacy is not just bare light source, it is how much power you need to illuminate the required area according to the illumination level standard you are after. And that uses to be defined as certain minimum level. And that includes the efficiency of the optics, so how much of the generated light ends up either lost elsewhere, or as overillumination of some places.
There the enormous size of the high power LPS makes any beam control leading to excessive fixture sizes, so much in real life a lot of light waste is just written off as acceptable losses, so your 180lm/W ends up as barely 100lm/W. Plus the high efficacy comes only with the high power packages (90W or so), so the light source needs to be pretty far/high away to cover an area corresponding to the power.
 Because the LEDs are small and mainly maintain their efficacy even with way smaller packages, it is not difficult to really utilize all of their light, par by the optics being more efficient in distributing the light where needed, part because the smaller packages allow more precise installations, so you need way less lumens for the same task. So even when as bare sources the LEDs could be a bit less efficient than the top LPS, when compared with the rest of the system the power requirement gets lower for the same task.


The only applications where the SOX may outperform are the really foggy areas where the monochromatic light supposedly offers better visibility.
But even with that I have some doubts: I'm highly suspicious for thatto be just an overinflated marketing BS, using just strong glary fixtures (the only way how the huge LPS could be used) to compare. No material used more practical distributed low power lighting... It seems the monochromatic light has the visibility advantage only at places where these lamps set root in the market, nowhere else...
But I don't have any experience in that area, so it is just my feeling...

@ Eleco: Did you read James' contribution at all?

I can buy HPMV/ovoid shape retrofit led lamps from Philips (Trueforce Core LED Public) which put out 6000lm at 33,5w input power, meaning 180lm/w and that includes the driver losses. That's on par with the very best LPS lamps. And indeed, they will surpass LPS if you count ballast losses.
They have a CRI of 80 which makes it more pleasant for residential areas too, than the purely monochrome LPS light. Can choose between 3000k and 4000k color temp (marginal difference in efficiency between those two). See: https://www.lighting.philips.nl/api/assets/v1/file/Signify/content/LP_CF_7165331_EU.nl_NL.PROF.CF/Localized_commercial_leaflet_TrueForce_Core_LED_Public__stad_weg___HPL_SON__nl_NL.pdf

Your grandpa's lamps are either obsolete or unfit for purpose, and should not be taken as the benchmark for LED lighting efficiency. Neither should someone take the color rendering-focused general lighting 94 CRI LED lamps as a benchmark for efficiency, unless you compare them to other light sources with the same CRI. Those things aren't meant for street lighting, but for home lighting.

If your demands for CRI aren't too important, i can also just go to the shop and buy a 485lm general lighting LED lamp that consumes 2,3w. In other words, 210lm/w. See: https://www.lighting.philips.nl/consumer/p/ultra-efficient-filamentkaarslamp-helder-40w-p45-e27/8720169188259

LED is objectively better. You can enjoy the old stuff, i do too. Hell, i have a SOX 18w sitting in my bedroom to bathe it in the calming monochrome glow. But never forget that the reality may differ from your personal preferences.

@Medved: if narrow band yellow light is needed, LEDs can do that too. For some reason my city installed LEDs that are roughly HPS color in part of my city.

It seems that some members are ether unwilling, to lazy or incompetent to understand what James (an actually person who works in lamp R&D !!!) has written. However it is again correct.

Bare effiency:
The highest effiency lamp i could find ist the Philips SOX-E PSG 91W. It has an rated light output of 17.500lm at an rated power of 91W (1)
the effeincy is then about 192.3lm/W
Thishowever is only the lamp.
Philips recommends for these lamps ist BSX 91W CWA ballast. In it´s datasheet it says it has losses of 16.5W.  (2)
As the ballast is highly necessary to run this lamp, these losses also need to be accounted for when judging the lamp effiency.
This drops the system efficiency to 162.8 lm/W
Meanwile Philips highest efficiency integrated LED lamp (With integrated ballast ) consumes  has one efficiency of 210lm/W (3).
For those who think i lying, see here links to the references...

(1) http://static.mercateo.com/fa/55a4782c9fa64b0ca4c95a263e6b7d67/pdf/master_sox-e_psg_v7.pdf?v=1
(2)https://magazynlamp.pl/file/32711/_.pdf
(3)https://theunissen.com/media/downloads/A008117-Datenblatt-Philips-MASTER-UltraEfficient-LEDBulb-4W.pdf?srsltid=AfmBOorbQfj2vL1u-MA_0GehmgdoHefDksU0hh80T3Ye_VwbnHO7Bgr8

To put in blunt, the desperate ignoring of fact in order to hang on the the myth that SOX-E is the most efficient light source to ever exist is exactly this: a myth. A myth that cannot be found in the stats. The stats and consumer preferences clearly shows it, gas discharge lamp as general light sources are obsolete, and have been that for a few years now.

Well, I'm not expert really at bulbs but on my Wattmeter, I measured how much watts does actually a 100w HPS bulb use and it uses about 180w to 205w. I believe the +80w to +105w is probably the heat in the bulb that increases the wattage where as, 100w is used to give light. Same it goes on a 400w MV bulb, its actual wattage is 440w to 460w but 400w is used on the light.

Correct me on the "+80w to +150w is probably the heat in the bulb" part. It could be the ballast that increases the wattage

Well, to be fair )

Using today's tech it is relatively simple to make electronic LPS ballast with say, 95% efficiency, or even better if cost and weight does not matter.

Next, stated 210lpw figure is related to relatively small 4W lamp which has a luxury to be able to run its LED chips significantly underdriven. With *serious* light sources, like 400W HPS equivalent streetlight engine, loading and power dissipation issues starting to take their toll eating off lpw figure so it will be somewhat less impressive.   

Well, I'm not expert really at bulbs but on my Wattmeter, I measured how much watts does actually a 100w HPS bulb use and it uses about 180w to 205w. I believe the +80w to +105w is probably the heat in the bulb that increases the wattage where as, 100w is used to give light. Same it goes on a 400w MV bulb, its actual wattage is 440w to 460w but 400w is used on the light.

Correct me on the "+80w to +150w is probably the heat in the bulb" part. It could be the ballast that increases the wattage

im going to talk to my cactuses. I think that convesation will be more fruitful...

Well, to be fair )

Using today's tech it is relatively simple to make electronic LPS ballast with say, 95% efficiency, or even better if cost and weight does not matter.

Next, stated 210lpw figure is related to relatively small 4W lamp which has a luxury to be able to run its LED chips significantly underdriven. With *serious* light sources, like 400W HPS equivalent streetlight engine, loading and power dissipation issues starting to take their toll eating off lpw figure so it will be somewhat less impressive.

indeed it ishowever it just answers this: Re: Is LED really the world’s most energy efficient light source? Actually it is alredy above the top to answer this. Comparing streetlichts can be done however will be more time consuming, however I predict installation to be similar.

Regarding more potent lamps a (bare) 70W SON lamps has an output of 6000lm. Philips HID Filament version consumes forth 4000K variety 28.5W and produces 6000lm.
in order to replace even higher powered conventional lamps, you will have to compare fixtures as making drop in replacements for these lamp is very difficult, mainly due to thermal management.

This love affair some people still have with low pressure sodium is truly getting tiresome. Yes I have many LPS lamps and fittings in my collection and yes I have pangs of nostalgia when I see them lit, or when I see old installations of them in-situ in photos. But for people to keep harping on about how much better they are than LED (which is quite subjective) without bothering to actually listen to experts on all forms of lighting who actually know what they're talking about is akin to those who keep saying cars from the 1970's were so much better than cars of today.

The only way they could be said to be 'better' is that they were simpler to repair, that is it. They fall short in every single other way compared to cars of today.

As someone who designs streetlighting installations as a job, I am constantly amazed at how much lower amount of power I can use to make an installation compliant with LED. I'm now using 113w LED's where I was previously using 250w HPS (plus a hefty addition in magnetic ballast losses). As well as the lower power use, most roads are now covered with CCTV and the white light is far better for those than orange is. Metal halide was trialled for a bit for this reason but quickly abandoned in favour of LED due to the short lamp life and cost of lamps.

Yeah I'll always have a soft spot for HID, especially SOX, but that is all it is. They'll live on our collections but not the streets, that is ok with me.

Exactly what I think! I like SOX and all, but objectively LED is far better. I'm currently doing some work with an astronomer, the flexibility of LED is something that no other types of light sources have. Led has extremely flexible dimming, schedules, monitoring, smart control, and they just make better use of the light given out. Just say 250w HPS emits 25,000 lumen and 175w led also emits 25,000 lumen (just as an example, these arent the actual numbers), an LED luminaire directs all of the light down, and where it is actually needed, compared to an SCO HPS lantern which puts the light around everywhere, including places where it isn't needed. Meaning that you can have a, say, 120w led lantern replacing a 250w lantern, making for even more savings.

HPS also causes issues for astronomers because the orange light can reflect off of the sodium layer in the atmosphere, which is used to create 'artificial stars' by shining a laser on the Sodium layer to calibrate telescopes. Led can get around this.

Finally, LED is also ever improving, the new LED luminaires of 15 years ago may have gotten 100lpw, now the new luminaires get to around 175lpw. No other light source has ecived that level or improvement in that little time AFAIK.

The Answer is "NO". The main light source that is actually efficient is LPS and the manufactures are stopping to make LPS bulbs as it's easier to make "LEDs". They don't actually car if a light source is efficient but if it's easy to make.

And also, SOX, which is basically an LPS bulb, can have 160lm to 180lm per 1 watt where as my Granddad's LED Streetlights uses 100lm per 1 watt  So what's more efficient?

Not basically, it is an LPS lamp. Lamp companies stopped making LPS lamps because people no longer wanted them, it's that simple. No company is going to keep making an expensive, highly specialised lamp like a SOX lamp if no councils, road departments or whoever don't want to buy them anymore. As for the lamp collector market, well this is extremely small and usually doesn't have a lot of money....

@Eleco_SR304 Look at these lanterns from the USA. These reach up to 168lpw and up 173lpw respectively.

https://www.creelighting.com/products/outdoor/street-and-roadway/guideway-series/?lang=en_au
https://www.led.com/evolve-ernc/530374

Keep in mind that most LED streetlights uses lens optics, which causes them to be superglaring, compared to HID and LPS optics.