I was wrong on the current cost of our electric power.
Our cost per kWh varies due to the way demand metering works.
Last months bill was ~$0.15/kWh.
Here is a Bitcoin Mining Calculator for the 3 types of miners we have
You can look at the text summary to see how much we lose on each type.
The Antminer S3 (not sure if we are Batch 3 (what I used) or Batch 5) - most efficient
The Antminer S2 - most BTUs (Watts)
The Antminer S1 - Oldest least efficient.
Since we have a heat pump - heating with the heat pump might save us 50% over pure resistance heating like the Bitcoin miners.
Even though we are not making a profit on mining it looks like with Bitcoin at $395 it would still be better to use the miners (S2, S3) assuming we can cycle some of the miners on and off with a thermostat. The miners would have to be pretty reliable even with the power cycling so that they are always mining when they are running.
We may want to consider running enough miners to keep the space at a fixed temp say 65 degrees (number of miners would depend on avg outside temp). Then we would use the heat pump when the space is occupied to quickly bring the space up to comfortable temperature.
We would want to turn off the breaker for the emergency resistance heat in the air handler.
We may want to think about putting the miners under the floor by each location where people sit. We would lose heat to the cold concrete though. This also happens when we run the heat pump since the whole space under the floor tiles is our return air duct.