Thanks for the numbers nwdiver; that will help a lot of people looking to upgrade their current home.
I'm not one for home improvement, so last month I moved to get a more efficient home. Some of the energy-saving features it has (I don't know the prices the builder paid so I can't give numbers like nwdiver did):
1.
Daikin Altherma heat pump for hot water. In addition to regular domestic use, this water is circulated under the floors to heat the house. The builder says this is the most efficient heat pump on the market; the marketing materials claim a COP of 4.0. I assume that's only in heat pump mode at a high-efficiency temperature; like nwdiver's system, when really cold outside a small electric resistance heater will come on. (The heat pump can operate down to -4 degrees F, but gets really inefficient). I'm in the Seattle area which has very moderate temperatures so I imagine the heating element will be used very rarely.
2. Polystyrene foam insulation. The wall panels are pre-built with insulating foam wrapped around them. Not only can you get far better than code insulating levels in far less space, but the foam wrap around the wood also prevents thermal bridging. Our old house lost a lot of heat overnight; in the new house I can wake up to the same temperature it was before bed even if it is over 20 degrees colder outside.
3. Passive heat recovery ventilator. For good insulation, the home is nearly airtight (seriously - they have to have a dedicated make-up air fan to replace air pulled out of the house when you turn on the range hood fan - otherwise it gets hard to open doors!). But of course the air in the house needs to be circulated. So there is a low-speed fan that runs constantly, and it runs the incoming air over the outgoing air to recover 65% of the heat.
4. Dual-pane PVC-wrapped windows. As nwdiver noted, triple-pane windows would lose a little less heat at night in the winter. But a quality seal, good coating and thermally tight wrap material make the difference small. Plus, with these windows I'll get more solar gain during the course of a year than I'll lose. Double-pane windows were the most efficient for this application.
5. LED lights (and CFLs; the builder used both. He also used a few halogens, but we are in the process of replacing those with LEDs). I never liked CFLs, although we switched our previous house over anyway. But I love LEDs.
6. All energy-star appliances.
The house has a 10kW solar system up top (so I get an $11k tax credit for buying the house, and about $1500/year from the state for generating electricity, plus I only pay my utility for net power used - which is, of course, covered under the Green Power program), and is certified net-zero energy and 5-star green. Unfortunately that's not considering EVs; but I am an owner in another solar collective so that can cover my cars.
A lot of people are afraid of "green" technology because of their experience with things like CFLs. But this stuff is not only saving me money, it makes for really nice living conditions. It's an all-around improvement, just like EVs. (The house also has some air and water management systems that are nice too; but those are off-topic so I'm just focusing on the energy stuff here. Oh yeah, most of the materials are at least partially recycled or sustainably harvested. Few builders go to that kind of trouble, unfortunately).
