I disagree that. It is not efficient simple reason that miners will not earn money back because difficult level rising all the time and when you use example 1000w keep miners running you will get only 1000w heat. If you use air source heat pump you will get 2000-6000W heat per one 1KW so it is much more efficient for heating than running miners.
So you have to spend 2-6times more electricity when using miners compared heat pump or other efficient heater to heat house for same temperature. Keep that mind when doing calculations.
I see your point, but you can't really compare the two.
Sure, if your goal is to use as little electricity as possible to heat your house, then there are more effective ways. Insulating walls, roof, windows and burning wood comes to mind.
Throw in a heat pump in the mix and you're good to go.
But, if you eitherway are going to mine, its more efficient to use the heat, instead of just pumping it out of the house.
This is how I do it:
Family and friends are heating their houses with 1000-2000W electrical heaters. So I replace their heaters with miners. I pay half the electricity.
They get: Same heat for half the electricity price.
I get: Location to host miner, half price on electricity.
This is how you ROI a miner today
I support Torepia answer on this.
The goal wasn't buying the miners to heat the house over my furnace. trust me it is far cheaper to use my gas furnace. The goal was to utilize the heat blown off the miners. Instead of blowing the heat elsewhere, I can use it to heat house.
At this stage in mining, it will take 6 months+ to get ROI mining straight bitcoin (depends on electricity cost). But most people who keep say "ROI is an issue" they refuse to mention or include the fact that reselling the miner will easily get you over your ROI. Even if you don't mine enough to get your ROI, the reselling will.
Look at prices currently on the marketplace section, ebay, craigslist, amazon, etc.