Students' Solar Decathlon vs. Real Market Homes:

How concept houses at college competition compare with what residential builders offer today


The buzz at the 2017 Solar Decathlon proved infectious, thanks to the human energy and excitement of the college students worldwide who participated in the October event in Denver. And as a professional in energy-efficient buildings, I was impressed by what the young people demonstrated: new concepts, some pretty amazing technology, well-designed and cool-looking houses, and their willingness to "stretch the envelope" (pun intended). The competition also gave me an opportunity to reflect on those ideas and new technologies, their applicability for today's new-home buyers, and finally how the decathlon concept homes compared in price to Zero Energy (ZE) homes on the market today.

Congratulation Teams

After visiting all of the concept homes, I want to congratulate each team for their accomplishments.  The winners were:

  1. Swiss Team
  2. Maryland
  3. University of California (UC) at Berkeley/University of Denver (DU)
  4. Missouri University of Science and Technology
  5. Team Alabama
  6. Northwestern University (in Chicago)
  7. Netherlands
  8. Las Vegas
  9. UC Davis
  10. Washington University - St. Louis
  11. Team Daytona Beach*

*Team Daytona couldn’t finish its concept home because Hurricane Irma disrupted their work, but the team made a respectable showing -- and actually provided a better behind-the-walls view than any other decathlon home.

Concept Heaven

I have always thought of this competition as a concept car show.  At major auto shows, automobile manufacturers display concept cars that push technology, aerodynamics, and materials even if the concept car may never be manufactured.  The solar decathlon is the same type of experience for zero-energy homes.

Since I’ve visited decathlon competitions before, I could compare the 2017 concept homes to earlier competitions. Technology has matured over the years; for instance, this year heat-pump water heaters were prevalent in the homes but a few years ago, concept homes featured student-designed electric heat-pump water heaters because no such water heater was available on the commercial market.

This year, too, all the homes had battery storage, as was an electric vehicles (EV) in the driveway of each concept house. Mini-splits were the predominant heating and cooling source, and made for simple zoning of the building enclosure.

Most homes bumped up to the decathlon rules (which limit the houses’ size), and came in around 950 square feet, with the house designed by UC Berkeley/Denver (DU) team coming in at a little over 800 SF.

 The homes were definitely livable, with some having two bathrooms, and others sporting kitchens that might be found in any typical, new residential development.

This year, I also noted the focus on integrating indoor living with outdoor living, as all the concept homes had outdoor living decks as an extension of the overall living space. The Northwestern team’s home had a very innovative, movable sun room room, and was designed to endure the harsh climate of Chicago, IL.

All homes had some kind of “dashboard” or mobile device interface to control the heating, ventilation and air conditioning; lighting, water usage, power generation and storage.

Many of the dashboards are-off-the shelf, unlike previous years when the systems had to be student-designed because they weren’t yet commercially available.

Further, unlike earlier competitions, this year many of the concept houses also used off-the-shelf smart thermostats.

How do Costs Compare with Reality?

As I walked among these very innovative homes, I wondered how real-world, new residential construction compares to these concept homes.  As part of the competition, the teams need to account for all costs and estimate a final cost.  Most homes lined up in the $400,000 range with the UC Berkeley/DU team coming in near $200,000 (the UC/DU team intend its design to support "stack-able" units (think: Lego) to help reduce cost of housing in the very expensive California Bay Area). As we all know, land prices greatly affect the cost of housing, which partly explains the difference in home prices in heavily populated California compared with, say, less-populated Alabama.

How do New Residential Homes Compare?

After reviewing SWEEP's list of zero energy buildings and DOE's Zero Energy Ready Home (ZERH) list, I started the comparison.  As with concept cars (which cost more than standard cars), the decathlon homes show higher square-foot costs because of the technology, construction time, and the costs of building only one unit.  That gives new home builders, whom I highlight below, an advantage, because they build in a production mode and have years of experience both in construction and contract negotiations. 

Today, a home builder constructing new Zero Net Energy (ZNE) or Zero Energy Ready Homes (ZERH), can be very cost-competitive compared with a company that offers only standard new construction (to which ZNE and ZERH houses are usually compared). As always, one of the biggest factors is land cost, which normally remains the same regardless of how efficient the new house is.  In many markets (especially in the Southwest), consumers can find zero-energy homes that are cost-competitive with standard-construction homes and that offer the kind of comfortable living space that today’s home buyers want.

Take a look at four, Southwestern builders

In Prescott, Arizona Mandalay Homes offers a 1,600 square foot, 2-bedroom and 2-bathroom ZERH home for $260,000 (including land costs).  (Remember, a ZERH home does not include solar or renewable power systems but is designed and ready for the addition of renewable energy systems).  Even if the home buyer adds a 6 kilowatt solar energy system for about $20,000, upgrading the ZERH home to full ZNE status would make the new home’s total cost an affordable $280,000 -- and that includes everything, such as land, and attached garage. It's also less than the median $310,000 price for a standard-construction home in Santa Fe, and far less than Denver’s $410,000 median price for a standard-construction house.

In Tucson, Arizona, Meritage Homes has a 1,612 square foot, 3-bedroom and 2-bathroom home starting at $195,000.  This house is nearly double the size of the smallest decathlon home but includes the land, attached garage and developed neighborhood.  Meritage can make all of their plans zero-energy.  This specific house has home automation, water efficiency, ENERGY STAR appliances, and is efficient without solar, at a Home Energy Rating System score of HERS 63.  Adding solar PV with a high estimate of $30,000 (Meritage uses higher output panels than some other builders do) still brings the home and land to a very cost-competitive price of around $225,000.  These prices are especially appealing to empty-nesters and first-time home buyers. 

The Revive development in Fort Collins, Colorado is a green community development with all homes following the U.S. Department of Energy’s ZERH guidelines. The Philgreen Construction team built a 2,100-square-foot, single-family home (including a flexible space that could be used as a separate apartment), with a selling price of $570,000.  And that price includes land costs and the expense of adding a solar-energy system.  The house uses a staggered-stud exterior wall design that achieves a respectable R33 energy insulation factor.  In addition, the home includes a ground-source heat/cooling system, with additional options such as electric-vehicle charging in the garage.

In Denver, Colorado, Thrive Homes offers a 2,098 square-foot, 3-bedroom, 2.5-bathroom ZNE home for $598,000.  Thrive builds homes with very efficient windows and 9.5-inch deep exterior walls, which allows for increased insulation.  The Thrive Zero Energy Now (ZEN) collection includes solar energy systems and meets the ZERH standards (including indoor air quality).  While the Thrive homes are $150,000 to $200,000 more than a solar decathlon home, the Thrive home also includes land and a garage, and is twice the size allowed at the decathlon, and is located in a popular new residential development.

Note that these Southwestern homes on the market do not have battery systems as standard features, which the decathlon homes do. That extra feature would add a cost of approximately $8,000 to the price of the real homes on the market. 

Market Changes

The ZNE/ZERH market is quickly changing from year to year.  More builders are looking at zero-energy programs as opportunities to support the needs and wants of today’s new home buyers.

California, with its big population and mammoth economy, is leading the push by instituting ZNE codes, so very likely national home builders will take these construction practices and model homes from California to other states.

Meanwhile, the renewable-powered concept home will continue to improve with future Solar Decathlons, and as excited, eager, and talented college students continue to push the envelope.

Thanks decathlon teams, for helping move the new home market, and the nation, toward greater energy efficiency.

All photos by Jim Meyers.

Jim Meyers is the Buildings Program Director at SWEEP. He is responsible for conducting analysis, preparing case studies, evaluating new and emerging technologies for buildings, and promoting the adoption of state-of-the-art building energy codes.