@gwagner in the California Bay area, mild climate. My monthly energy bill went from $200 in gas to $50 in electricity during the cold winter months. And we use it way more, too (i.e. way more comfortable; fewer sweaters and blankets and less shivering), since we can heat or cool just one room at a time, vs burning 1 therm/hr to heat two humans and a cat. Also, now this is the first time I've ever lived with a cooling system. Bonus: free midday cooling in summer thanks to rooftop PV solar panels.