Step 1: get summer to zero as cheaply as possible. Step 2: evaluate the combo of sources to get winter to zero. Step 2 will likely involve insulation, potenti

Step 1: get summer to zero as cheaply as possible. Step 2: evaluate the combo of sources to get winter to zero. Step 2 will likely involve insulation, potential energy storage (pumping water uphill to turn a turbine later), high thermal mass "heat batteries", solar that got us to 0 during the summer, wind, and water and maybe even nuclear.