Two of our air conditioning zones went out this summer. We decided to replace them with heat pumps. We couldn’t be happier. In addition to the energy savings, they are much quieter than the air conditioning systems we had before, and the temperature control is much more precise. Also, while the installation cost was slightly higher than a conventional system, because they use less electricity, and the relevant rebates, the increased cost will pay for itself in just a few years.
If you do go this route, we would strongly suggest you look at a system like Bosch or Daikan that uses an inverter technology. As I understand it these systems, vary the level of the heating and cooling depending on the situation, rather than just being “on or off” like more traditional systems. These account for greater energy savings, more precise temperature control, and quieter operation.