1) Choosing the right spotlight model : MR16, GU10, PAR20 etc...
a) GU5.3 (also called MR16) are small spotlights with 2 pins (pin spacing is 5mm) and have a typical diameter of 50.0 mm or 1.95", the power source is 12Volt DC or AC low voltage.
If you have recessed light fixtures, then the transformer is more likely integrated into the housing. Old transformers (magnetic) are heavy and make a small noise like the old shaver plug in a bathroom, they will reduce the 120V AC to 12V AC, but they are 100% compatible with LED lights and they can be dimmed as long as the LED lamp is DIMMABLE.
Newer transformers are called Electronic Transformer or high frequency transformers. They are small and light, some low quality ones make a high pitch (frequency) noise.
These new transformers need a minimal load, some models need as much as 10W to work, others 2-3w, they have been designed for Halogen 35w or 50w bulbs. Some are dimmable and some are not.
The minimal load is very important because a LED MR16 spotlight uses 3w to 6w which is under the minimal load or at the limit.
This is the reason that most MR16 LED do not work with these light fixtures.
If you want to upgrade your MR16 halogen to MR16 LED, buy at least a 5W version (3w or 4w will not work properly or not at all).
If you have 1 transformer that powers multiple MR16 lights than your OK for upgrading to LED’s
If you are renovation a home or doing a new recessed light installation, then I suggest to NOT choose the MR16, go with a GU10 type.
If you are using MR16 in counter displays, you are more likely using 1 or more transformers to power multiple MR16.
The advantage is that you can run a lower gauge cable to connect each MR16 to a transformer, saving space and money.
Also some "Electronic Transformer" with output 12V DC and NOT AC. Lab test has proved that LED MR16 lights gives their best performances when using DC voltage (up to 10% increase in Lumens).
b) GU10 are the 120V version of the MR16, same size. The only difference is that they are powered directly from the 120V source.
If you are doing a new reno, this is your choice. There is not transformer involved.
c) PAR16/PAR20/PAR30/PAR38 are all 120V version with a screw base socket. There is not transformer involved.
PAR20 is about 20% to 30% bigger than a MR16/GU10 bulb. Due to their bigger size, that means more heat dissipation capability,
PAR lights are good choice when you need more than 50W (halogen replacement). They usually starts at 6W and can go up to 18W.
2) Difference between Halogen and LED spotlights
Halogen lights are much brighter than regular incandescent lights, they are widely used in recessed lighting. Their lifetime is about 2000-2500 hours (1 to 2 years depending on brand/quality and usage) but they are affected by the ON/OFF switch effect.
For example a halogen spotlight that is turned on and off 4 times a day will last much longer that the one that is turned on/off 20 times a day.
LED spotlights on the other hand consume about up to 80% less energy than halogens for the same light output, their lifetime is 20000 to 40000 hours (that is 10 to 25 years) and are NOT affected by the on/off switch effect.
Halogen/incandescent and LED lights both become dimmed after a certain time of usage. they will loose up to 30% of their brightness, you will not notice it because it happens over time.
Related:
Choosing and Buying LED spotlights Guide (II)
Choosing and Buying LED spotlights Guide (III)
Choosing and Buying LED spotlights Guide (IV)
Choosing and Buying LED spotlights Guide (V)
