Just wanted to report back success here. I did order an EL1499ICA online, although what was shipped was an EL1499ICA-L, noted only on the mfr site as an economy version - but looked dimensionally similar to the original specs. I scheduled to have the electrician do it, less about the electrical than worrying about traversing 20' of attic and accidentally stepping through the ceiling drywall somewhere. Was very simple 10 minutes for the electrician to swap out the entire housing. Before he came, I did look at the housing and there is no way to remove the rectangular sealed box to just replace the transformer - it's basically riveted shut. He was the original electrician from the remodel - said 1 in a 100 of these fails, no good reason... I asked about what happens if one of the downstairs transformers fails, given no attic. He did confirm he could also access from the can itself via the ceiling, as brickeyee said, but it just takes more time and effort that way. I did see that removing three screws allows the can to drop out, although it did seem quite a pain to try to unscrew the old transformer from the housing blind (when your hand and screwdriver have reached into the opening). Would be a very challenging DIY attempt. Replacement housing works great, and learned a few things as a general DIY-er. Thanks, esp brickeyee, for the advice.

I assure you I can do the math. I was comparing LED to halogen - which is what the OP was asking about. But since you asked: The CFL cans that we have in our kitchen and a few other places are Juno ICPL626EN. I just looked around the net and found them for about $60/can, plus another $22 for trim, and $5-10 for the 26 watt bulb. That works out to about $90 per location. The bulb is rated at 1800 lumens, But I think due to the bulb and trim design less than half that actually makes it downwards. (Not measured.) They take about a minute, literally, to come to full brightness. Annoying as all get out. Contrast to a cheap 6" can with a CR-6 at about $50 per location. All 575 lumens pointed down, so no fixture losses. instant on, beautiful 92 CRI light quality, and they dim. And they only draw 9.5 watts each. Do the math. Even if I needed twice as many CR-6 to get the same illumination levels (which I doubt), I'd still be money ahead with LED in the end. In our MR-16 fixtures (mostly 12v for wall washers, but also a 6-light track light that uses GU10s), CFL really isn't an option. The few I have seen get horrible reviews. It is halogen or LED. Four years ago we used halogen. But because some of these are very highly used, I have replaced most of the 12v ones with the 10 watt Philips LED - which are easily as bright as the 50 watt halogens. At the tier 3 energy rates of about $0.30/kwh payback is less than a year.

What I have now is low-voltage xenon lights with internal transformers inside each fixture. I'm looking at replacing them because of continual problems, like multiple burned-out bulbs and a burned-out transformer after 16 months, and innards so full of wires and wire nuts that the fixtures pop apart if I removed the glass diffusers (or spontaneously in the case of the smallest strip.) Judging from online reviews, these are common problems with the model that I have. We have line voltage coming out of the walls for the three separate runs of lights, all on the same circuit. If I understand correctly, the electrician can use the existing wiring to install either low-voltage lights with internal transformers (NOT the same brand!) or line-voltage lights. I bought the lights we have based on looks, function, and the showroom salesman's recommendation. Never would have thought to ask to see the inside of the fixture, though.

fluorescent bulbs under cabinets will be T4 or T5 ; these are long and thin -- think of light sticks, not round / spot / pucks. I gave you search terms. I'm sure you will find out stuff. All bulbs generate Some_Heat; the wattage is a key indicator of heat. Xenons are in the same family as halogens and old-fashioned incandescents (the bulbs we had in the 20th century), which is not efficient technology in terms of producing light (as opposed to heat). Searching, I read that xenons are only 10% cooler compared to regular halogens. That is still Hot. So incandescents, all types including xenon-halogen, make more heat than the other means of producing light (fluorescents and LED's). Fluorescents give more lumen (light) and less heat than the incandescent family (xenons, halogens). Fluorescents come in the range of 6 watts to 25 watts; that is fewer watts than the incandescent family needs. Incandescents use more watts to match the lumen, and the extra electricity goes into heat production. They are a heater and a light. LED's come in the range of a fraction of a watt. LED's are lowest wattage but they are so weak they don't produce much lumen (light). So they are good for accent lighting. If you buy large numbers you will get more light. you would have to install hundreds of them, to match the 1000+ lumen output of fluo or incandescent. Has anyone out there installed a hundred LED's under a cabinet? HTH -david