15 SEER minimum

All electric or nat gas service available? There is always Geo HP if in an all electric situation.

Size of home?

IMO

The question is how much is it going to cost you to upgrade to more efficient equipment. Builder's usually charge a lot of money for any upgrades. Get all the model numbers of the basis equipment and the upgrade.

There is no natural gas. We will be all electric and using propane for cooking.

There are two ways to go (at least). If your construction is super-insulated and sealed, there is much less gain from higher efficiency mechanicals for heating and cooling. If not then there is.

If I were building a new home, I'd seriously consider hiring an energy rater to help design and to build in performance benchmarks that the builder must meet. They can run numbers for you and help you decide where to put the $ for the highest benefit.

After design is done, the benchmarks are important. The best design can be undercut by poor construction leading to air leakage, duct leakage, and poor insulation quality. (Even the best windows will leak are around them if not installed properly. Spray foam is often poorly mixed,....)