TL;DR
using/generating energy always emits heat as waste and there is an upper limit of efficiency that we are not that far from. if that energy was generated via something that is not a natural heat gradient for the earth’s surface there is a net increase of heat in the earth system simply by generating and using energy.
a lot of energy sources fall into this: fossil fuel, nuclear, geothermal, etc. two that don’t are (certain types of) solar and wind, since their energy would eventually be dissipated onto earth’s surface whether we intercept or not.
that waste heat is currently estimated to be ~2% of the heating power caused by global warming, so already significant. we essentially have an upper limit on sustainable energy usage on earth (and therefore an avg per person usage) or we will have Global Warming 2: Waste Heat Boogaloo.
That doesn’t really change the picture much. A typical coal-burning power plant turns about 1/3 of the energy in the coal into electricity. Highly-efficient combined cycle gas turbines might turn 60% of the energy in the gas into electricity. That energy is the amount of waste heat that those devices produce.
turbines are still energy generation, heat is also emitted when that produced electricity is consumed.
all machines have efficiency < 1 and therefore emit heat when used. many of those machines even have the goal of producing/moving heat.
All machines produce heat equal to their energy input. They have an efficiency of 1.0 at producing heat. Some will store it in potential energy for some period, but unless that reaction was exothermic, that potential energy will itself be released and fall back to a lower energy level, usually releasing it as heat.
Yes, but the amount of heat they’re generating is by definition no more than the amount of energy in the electricity. This caps the total waste heat impact, and means that for fossil-fuel-generated-electricity, their impact on the earth’s temperature is almost entirely a result of warming caused by the greenhouse gases emitted.