Miners use no more electricity than an electric heater. 100% of the electrical energy "used" by the miner is converted to thermal energy (heat). Of course in most places there are more cost effective methods of heating a house such as natural gas furnace, propane, or heat pump.
True, and as you say, the electricity draw is only equivalent (well, for the most part) to a space heater in terms of "heating" up a space (in fact, I think a website did a study on this).
If there was a way of having multiple sources of heat through mining (having small miners embedded in different locations with fans circulating the heat, or some sort of schematic like that), and the system's electricity draw is at (or just marginally more) than the electricity draw of one of those houses with the more efficient electric heating systems, that'd be awesome.
I think we
will see bitcoin miners used as heaters moving forward in time. It all comes down to how one can heat his home most cost-effectively.
The majority of apartment buildings and even many smaller houses in my area use electric baseboard heaters. These devices perform the following conversion:
1 kW of electrical power -> 1 kW of heat.
Imagine making a new device that instead performs this conversion:
1 kW of electrical power -> 1 kW of heat +
X bitcoins / day
Which device would a rational economic actor choose to heat your home? The answer is that he would choose the bitcoin heater
if the extra cost he pays overtop of the price of the simple heater is less than the revenue he expects to earn from mining.