Originally Posted By: Johnny2Bad
LEDs are increasing efficiency at a very good rate ... the units available in five years will generate half the heat for the same light output at those available today, and those are very much advanced over LEDs of the past.
If you lose a light source this morning, you need to replace it today, not five years from now. So use what is available.
It should be noted that light efficiency is based on the assumption that heat is an unwanted side effect of operating the device. If you live in a northern climate, or you have lighting in an area of the home that is unheated but less than 68F, then the heat output is ** wanted ** output, not unwanted output. Thus the least efficient type is now 100% efficient, as both the heat and light are wanted output.
Electrical heating is 95% or better in efficiency. If you have one of the latest super-high efficiency natural gas furnaces you can equal that. Where electric heat is inefficient compared to the most recent Natural Gas heater technology is at the Power Plant, which can be as little as 70% efficient but also could be higher, depending on how your local utility generates electricity. Now it's a matter of your Natural Gas heater (how old is it?) versus your Power Plant (is it nuclear? Very efficient) as far as what is least damaging to "the Planet". Older furnaces can be less than 70% efficient.
If the area is one that uses supplemental heat ... ie you have a Natural Gas furnace and the lamp is in an area heated by that furnace, then changing to a more efficient bulb will mean you will use more Natural Gas to replace the lost heat provided by the lamp. So you have gained nothing; you reduce one bill and increase another for the same net result.
Ideally you would use incandescents in winter and switch to LEDs when the air temperature is above about 70F, and back to incandescents in the fall. But of course regulators realize no-one will do this, so they ban incandescents and conveniently fail to mention the increase in winter heating load that will result.
As always, it's not the information you get that matters, it's the information held from you that matters.
There is an exception to your story and that is if you have a heatpump based heating.
Heatpumps provide much more than 100% efficiency in heat per watt of electricity used by including the outside environment as part of the thermodynamics equations. Most heatpumps should have at a minimum of over 100% efficiency except in the most extreme climates.
If you are doing the thought experiment of switching your light bulb type in the name of efficiency, this doesn't make sense, you should instead think even further outside the box (literally thinking outside the house as a closed system) and jumped to a heatpump based heating solution, which then renders all that busywork of swapping lightbulbs seasonally a moot point.