Thanks for the link; I hadn't heard of them before. I can absolutely see a system similar to this being the future. With an additional water loop, when running

Thanks for the link; I hadn't heard of them before. I can absolutely see a system similar to this being the future. With an additional water loop, when running in 'AC/cooling mode', the waste heat could be captured for the domestic hot water tank as well. As with solar, energy/heat storage is likely to be an important component of the solution. Even without TOU rates, areas like mine (Mid-Atlantic) can hit temps at night that start to tax heat pumps (low teens F). However, the next day will often be above freezing and sunny. The HP could 'bank' available heat during the day to handle the late-night chill.