The first thing to reduce energy is to see where it is being wasted.

 An energy audit with blower door test and infared camera is the best place to start. 

 The list of upgrades range from adding insulation, to replacing HVAC systems and everything in beteen, such as new windows and doors to installing smart theromstats. But because each home is different and has different needs the only way to be sure your upgrades are right for your home is to start with an energy audit.

Get with a local solar company and have them look at your plans.  You may be building a home that cannot work with solar due to your roof pitch, orientation or shade.  Let them give you a site assessment and run the financials based on your available incentives.  You can look them up here:  http://dsireusa.org/

Since 80% of a window is glass, it is always wise to pick the right glass for the direction the window faces in your home.  LowE 366 Argon filled glass for the south and west exposures may be the best fit.  LowE 272 Argon filled glass for the north and east exposures might save you money and be just fine in those locations.  Visable light will be something you want to check if you have plants that require lots of light to grow.  The higher the number the more light for the plants.  Any window that has a U value of .27 or lower will be very energy efficient in both the summer and the winter.  Double pane vs. triple pane may make a difference, so be sure you review the manufacturers specifications before you make that decision.

The other decision you have to make is what kind of frame you want the window made of.  Vinyl, wood, wood clad and fiberglass are the main options you will have to consider.  Each has their plus and minus points.  However, as I stated above, 80% of a window is glass and most quality windows have the same glass options from the same manufacturers, so be sure you pick the right glass with a low U value and you should be happy.

Also, keep in mind that installation of the window is just as important as the quality of the window and the glass that is in it.  I advise you to get two or three bids and check each contractor out to make sure they have happy window clients.

The shape of your roof will definitely have an impact, but generally speaking, solar pays for itself in spades.

The other thing to consider is that solar is ideally tailored to your personal electricity requirements, which you won't know for sure until you've been in the house a few months (a year, for a complete picture). You're probably safe installing a smaller system (which is what you usually find on new construction), but you'll likely find it won't cover everything. If you decide to go forward now, just make sure the system is expandable down the line; this is one of many reasons you'll want microinverters as opposed to a string inverter.

Good luck!

I have yet to survey a home that didn't need additional insulation and more importantly....air sealing. 

While HVAC systems are typically older in most homes that we audit, every home that I have ever been in leaks too much air and much, much more than is required.

Air Sealing and Insulation would be #1 and #2 on my list.  After that, items like HVAC and windows will jockey for position depending on the condition of both. 

Solar Panels are increasing in energy generation and energy storage is getting better and better.  You definitely need to make sure that your dwelling is positioned on the property to maximize benefits.  While it is way down the road, make sure to investigate the implications of what happens when the day comes to replace your shingles.  I would make sure you also have adequate insurance in the event the panels are damaged by hail, trees etc. and that you have a comprehensive maintenance program in place should you elect to have panels installed.  You may want to check with your local building code authority and see if you are able to have solar panels on your property other than on the roof if you have enough space.  Just like the VCR, solar panels are coming down in cost and going up in efficiency, so you may want to wait.  If you could have many less panels in the near future, that produce more output, that may be the best choice. Here is a link of many residential applications https://images.search.yahoo.com/search/images;_ylt=A0LEVzpL309ThhkA45xXNyoA;_ylu=X3oDMTB0YXQwZXBpBHNlYwNzYwRjb2xvA2JmMQR2dGlkA1ZJUDQxNl8x?_adv_prop=image&fr=yfp-t-745-s&sz=all&va=solar+panels+homes