Bumbling round the Net looking at geo-thermal heat pumps as a possible replacement for our oil-fired boiler, now that fuel prices are so high, I stumbled across solid state heat pumps: The 'Peltier' effect, where application of dc current across a semiconductor causes the device to pump heat from one face to the other, by means of electron transport. With a COP [coefficient of performance] of up to 0.7, not of much interest.
But further digging revealed a new technology called CoolChips[TM], in which a vacuum-gap of 30-100 Angstroms allows " thermotunnelling", or the passing of electrons across a very small space with much improved electron transport. This is claimed to have the potential to outperform Peltier devices by 11 times, [ COP = 8 ] and thus beat conventional heat pumps or air-con compressor/evaporator devices by 18%, with a Carnot cycle bettering 55%.
So, if electrons can transport heat, in the same way as a refrigerant - does that mean an electron can get hot or cold?

Sure, and you can pick out the really cold ones, they're wearing little jackets.
(Sorry, I couldn't resist).

Actually, I don't think so. It's more likely an effect of passing a current thru a junction, similar in a distant way of passing a current thru anothet type of junction which causes it to emit light. We never think about which electrons are brighter, it's just the effect of the current flow thru the particular junction.

Electrons can have more or less (heat) energy associated with them. Electrons in orbits around a nucleus will jump to a higher orbit shell if they absorb enough energy. If they absorb energy but not enough to jump to a higher orbit shell, they will just emit a gamma ray (or x-ray or photon) to lower their energy to that required for the shell they are in.

Loose electrons, or any other particle, will exhibit a change in energy level by a corresponding change in their kennitic energy (velocity).

Keep in mind that no one really knows what an electron really is. We observe their behavior and make theories, but what they actually consist of is pretty much up for debate. No one has seen one, and never will.

Radar