The table below, lists the energy content and approximate cost for different solutions. Natural gas isn't available where we're building, but I included it in the table for comparison. The efficiencies listed for Air and Geothermal heat pumps are just approximations.
The next table shows the approximate BTU heat load for various aspects of the structure and the cost of providing the heat using different solutions. As mentioned in previous posts, the biggest opportunity for savings is by making the structure more airtight and improving the air infiltration.
To summarize, heating with an Air Heat Pump will cost approximately $1300 / year, based on the estimated baseline heating load and current cost of electricity. We will keep improving the design from this point.
In addition, going all electric will avoid the costs of installing an underground propane tank and plumbing the house for LP.