The question revolves around buying the most efficient lighting. I started wondering whether there are LEDs that are more efficient then others on the market? or are they all the same? Google didn't seem to provide the answer to that question. Thanks
Do LED lights vary in efficiency?
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chrisski
Solar Boondocker
I think they are the same or close enough, but best thing I found was to go to a site like superbrightled.com and go to the bulbs and compare specs. Least that’s what I did Looking for LEDs to replace incandescnt bulbs in the RV.
Look at watts, amps, and volts compared to Lumen output.
I found that the less amps or watts in an led, the less Lumens, bright it was.
Look at watts, amps, and volts compared to Lumen output.
I found that the less amps or watts in an led, the less Lumens, bright it was.
BentleyJ
Solar Wizard
A typical store brand LED bulb has an efficiency of about 100 lumens per watt so should produce 800 lumens with 8 watts which is considered equivalent to a standard 60 watt light bulb. There are higher end products that are reaching 150 lumens per watt even up to 200 lumens per watt but are not usually stock items.
As @chrisski said, compare wattage with lumens. In the UK, a non-dimmable 475 lumen LED lights vary between about 4W and 5.5W consumption depending on manufacturer.
Then there is the separate issue of perceived brightness due to colour temperature. 'Daylight' or 'cool-white' bulbs will appear brighter than 'warm-white' despite having the same lumen output.
Then there is the separate issue of perceived brightness due to colour temperature. 'Daylight' or 'cool-white' bulbs will appear brighter than 'warm-white' despite having the same lumen output.
Quattrohead
Emperor Of Solar
Yes they do, greatly. I have some old Osram that use 77ma for their 800lm and some off brand that use 187ma to make 800lm.
There's a wide range. Luminous efficacy is measured in lumen per watt (lm/W). An incandescent lightbulb has an efficacy of 10-15 lm/W.
Commercial LED bulbs range between 50 lm/W and 200 lm/W, most common bulbs are in the 90-130 lm/W range.
Differences come from:
- Optics and how much light is lost in the diffuser
- Type of LED used
- Efficiency of power conversion electronics inside the bulb
- Cooling
- Number of LEDs.
LEDs lose efficiency at high current and high temperatures. The 200lm/W bulb uses about double the number of LEDs than the usual, so they run cooler and at low current, which makes them more efficient.
This also means closed luminaires that cook the bulbs won't just shorten their life, they'll also reduce light output.
Unfortunately, producing red is less efficient than the other colors, so the more efficient bulbs tend to be high color temperature with not so good color rendering. Personally I like these bulbs, nice 3000K tint, good color rendering, and they last.
KITROBASKIN
Solar Addict
Typically the warmer color temperature LED´s require more phosphor to turn a blue LED into a variation of white. This will reduce their ´efficiency´ but make your indoor environment more pleasing to more people. Consider that light quality (and color rendering) are desirable goals when one considers that we use those indoor spaces a lot, and light can influence mood. Maybe try different variations with decent quality bulbs before making the big investment in your lighting needs.
RCinFLA
Solar Wizard
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Most white LED light bulbs use indirect excitation of phosphors from UV LED's similar to a fluorescent light bulb. If you look closely at the actual LED you will see a small dome of yellow colored material which is the phosphorous material. They change the phosphor mix to get different light color temperature, soft white (2600-3000 K), cool white (4000-6000 K), etc. Higher color temp bulbs have higher lumens output for same wattage but light is harsher blue-white color.
There is some variance in the emission from LED itself, variation in the quality of phosphorous material used, and big variability in the electronic driver circuitry. LED's need to be driven with a current source. The phosphorous material does degrade in visible light generation over time.
Worse efficiency is in many LED light strips that just have a ballast resistor in series with each individual LED from 12 vdc bus bar. Up to two thirds of applied power is heat in the ballast resistors. Some string strip LED's are series connected, like some Christmas tree light strings. These can be fed from an electronic ballast that provides the current source to the string. Downside is if one LED blows out whole string goes out.
For most normal house LED light bulbs, the electronic ballast is usually the weak link. They are usually the cause of premature failure of LED light bulb. Most use a simple rectifier-electrolytic filter capacitor from AC mains to feed a DC to DC current source converter. The electrolytic filter capacitor is usually the weak link in the electronic ballast. Many LED bulb electronic ballasts cannot be placed on a light dimmer so you need to carefully check the box labeling to see if a particular LED bulb can be placed on a dimmer. The ballast design is different for a dimmable LED bulb.
The simple rectifier-filter capacitor for AC to high voltage DC conversion gives them a poor power factor caused by high, short period current crest factor. Typically around 0.65 equivalent power factor. If you measure the AC current and multiply it by AC voltage you will get a volts x amps number that is over 1.5 times the bulb's wattage rating.
When running from a battery powered AC inverter, inverter losses are based on output current load so a poor power factor load creates higher inverter losses although for a small wattage LED it is not very much additional loss.
There is some variance in the emission from LED itself, variation in the quality of phosphorous material used, and big variability in the electronic driver circuitry. LED's need to be driven with a current source. The phosphorous material does degrade in visible light generation over time.
Worse efficiency is in many LED light strips that just have a ballast resistor in series with each individual LED from 12 vdc bus bar. Up to two thirds of applied power is heat in the ballast resistors. Some string strip LED's are series connected, like some Christmas tree light strings. These can be fed from an electronic ballast that provides the current source to the string. Downside is if one LED blows out whole string goes out.
For most normal house LED light bulbs, the electronic ballast is usually the weak link. They are usually the cause of premature failure of LED light bulb. Most use a simple rectifier-electrolytic filter capacitor from AC mains to feed a DC to DC current source converter. The electrolytic filter capacitor is usually the weak link in the electronic ballast. Many LED bulb electronic ballasts cannot be placed on a light dimmer so you need to carefully check the box labeling to see if a particular LED bulb can be placed on a dimmer. The ballast design is different for a dimmable LED bulb.
The simple rectifier-filter capacitor for AC to high voltage DC conversion gives them a poor power factor caused by high, short period current crest factor. Typically around 0.65 equivalent power factor. If you measure the AC current and multiply it by AC voltage you will get a volts x amps number that is over 1.5 times the bulb's wattage rating.
When running from a battery powered AC inverter, inverter losses are based on output current load so a poor power factor load creates higher inverter losses although for a small wattage LED it is not very much additional loss.
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efficientPV
Solar Wizard
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Initially, many low voltage fixtures were hard to find. I modified several flush mount LED fixtures to operate on low voltage. These 11W LED operated at about 40V. I pulled out their electronics and added a boost converter to raise the voltage from 12V to about 33V. Plenty bright and far more efficient, Just like the"Dubai lamp" does. Lower current + higher efficiency and longer life. If you chase most lumens, most likely you will get an inferior lamp.
Yes, our eyes' sensitivity for green is very high but not so much for red, and the lumen unit takes eye sensitivity into account, so red usually has very poor lumen/W. This means if you want good color rendition, people to look healthy and not a sickly shade of zombie-grey then you have to pay the red tax and lose some efficiency.
Basically you can get good lights (CRI>95, good R9) at 100lm/W, decent lights at 150 lm/W, but the super-high efficiency 200lm/W lamps I tried were all garbage, CRI80, no reds, greenish tint, disgusting. I haven't tried the Philips though.
KITROBASKIN
Solar Addict
Is it true that older, more established white LED´s use a blue LED under the phosphorous material? And that more modern emitters have a more purple die? Is this to render reds more effectively?
Yup, the poor power factor can also create extra "noise" (especially on smaller HF inverters) due to the uneven loading. This is exactly why I'm looking for lights with good PF. There's a handful of common designs, but it's hard to know without buying and cracking them open; and while some places do that they often don't also test if the rated lumens are accurate (not all are).
As far as strip lights, I've love to find some 12/24/48V ones that do NOT use massively over sized resistors while over-driving the LEDs (common 12v strings do 3 LEDs and a resistor which means you're dropping ~2v and 20-30mA per parallel led, and if it's a "5050" size thats 3. In a typical "300" led string of 5050 size you're looking a turning 12W into heat. The "advantage" is this give the strip a VERY wide range it will run at, at the cost of efficiency.
I have seen some strips that use current limiting ICs, but I don't have one on hand to check to forward voltage Drop of the LED packages and test how well wasted power scales with changing input voltage and/or using PWM dimming.
There comes a point when looking at adding more batteries makes you wonder if you've spent enough time/money on not WASTING all of that stored power. Plus in the case of LED bulbs if I'm buying them *anyways*, why not get ones that wont make me angry later?
Personally lumans per watt (and possibly more importantly per VA) is what I'm chasing. not over-driving the LEDs makes them more efficient AND last longer, a win-win in my book! Wish I had a good setup to test lumen output to find the right spot on the curve however.
Theres a few variations, blue, purple, purple+nearUV (it's possible theres ones that are fully into UV but I doubt it due to safety concerns and lower efficiency of photons per watt). It's easy and cheapish to bump photons "down" (blue to green or red, green to red, and many shades inbetween) but a bit harder and usually less efficient to bump them UP (green to blue, for example). Generally speaking the shorter the wavelength the more energy the photon has. There's also all sorts of complications with the phosphors (usually a mix of several) and efficiency there.
Of course it matters little if you have an LED which can output 99CRI and magical 300Lm per watt, if the driver circuit is a half bridge feeding a cheap regulator while overdriving the LED
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