24-volt photovoltaic system with Solarex photovoltaic panels, Rolls batteries, Trace inverter and RV Power Products Solar Boost 50 charge controller. Hybrid electric system includes Onan propane generator backup that turns on with a flip of the switch in the house, or can be set, with the Trace inverter, to turn on automatically when the batteries get below a certain level.

Passive solar heat in the main part of the house is backed up with in-floor radiant heat, operated with propane boiler and energy-sipping 24-volt pumps to circulate the hot water. (There also is a wood stove in the great room.)

Solarthermal panel heats Domestic hot water via a heat exchanger tank, and is backed up with a loop off the propane boiler.

Southern wall of house has large, low-e, triple-pane windows.

Electric appliances include Sunfrost refrigerator and a Conserve chest freezer surrounded by 8" of beadboard insulation.

Washer is Frigidaire energy star front-loading washer with no always-on electronic panel. For clothes dryer, there is a clothesline out back, and room in the sunroom for drying clothes on a rack in the winter.

Although the listing says the house is "stick built", it is actually 80% logs.
Opening the windows in the tower in the summer creates an updraft that allows heat to escape the house. 
Eaves over south windows allows sun to enter in winter but prevents sun from shining in the summer.