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To solar carport or not to carport, that is the (or at least a) question …

January 29th, 2015 · No Comments

Most people think and most analysis occurs in a stove piped fashion. Difficult in conception and more costly in resources (whether brain cells, time or cash), narrow and constrained thinking often fosters not just far from optimal but simply bad decisions.  This is true across virtually all of human existence. The energy arena is far from an exception to this problem. From not considering life-time electricity use when buying Christmas lights to using the ‘commodity’ price rather than delivered cost (“fully burdened cost of fuel”) in military procurement decisions to only discussing energy savings returns off insulation or new windows without talking about comfort or health benefits in the house to ignoring the productivity benefits from greening workplaces (and schools), the limited nature of thinking when it comes to energy and environmental issues is hard to exaggerate. (And, of course, these are only benefits ‘within the decision-maker’ rather than all the externalities (both benefits and costs) that are left out of the economic transitions.) The all-too-often limited lens restricts us (all of us) to sub-optimal or simply wrong decisions.

Thinking about solar carports provides a window on this issue.

A recent email correspondence with a top-notch scientist about solar carports provides a window on the challenge of thinking narrowly versus the difficulty (but greater accuracy) of broader analysis. In discussions related to the Solar Roadways concept, we had the following exchange:

A. Siegel

What makes Solar Roadways really intriguing is trying to figure out all the systems-of-system benefits and relationships. It really is complex, on numerous levels.  Think about solar covering to parking lots in the same way — there are, most cases, cheaper/easier ways to put up solar panels but … but … it increases the value of the parking lot.

  • One Navy solar installation in San Diego covers a good share of a parking lot for sailors’ cars when they go on deployment. Can you guess which part of the parking lot is always full?
  • If you have a shaded parking lot, at the end of a hot day a car will be much cooler and thus there will be a far lower demand on the air conditioning system.  Lower gasoline use with lower pollution resulting from this.
  • When businesses put up solar parking spots, they find that those spots are generally the preferred spots — people fill them up quicker.  I’ve seen time lapse photo runs from multiple sites showing this.
  • The shade reduces heat extremes and thus reduces maintenance cost to the parking spot.BWP After Photos.078
  • Dependent on design, the solar covering can help channel rain/snow which reduces snow removal costs,  can make the parking lots safer (fewer icy patches), and can provide an eased path for water catchment (such as providing water for landscaping).
  • There is potential reputational value — whether with employees, customers, and the general community — due to the prominence of solar carports vs rooftop mounts. (On this, until they eliminated their solar division, I thought BP should have been installing small solar facilities at their gas stations with limited battery backup — during power outages, they would have maintained an ability to pump fuel on top of the reputational value of showing tangible measures to go “Beyond Petroleum”.)


I think there’s a strong case that if you DO have a carport, you might as well put solar panels on it. Sure.Where I am not convinced is that there’s a case that if you are looking for a place to put solar panels, a new carport installation over a parking lot is better than a roof or an empty lot.

Someone in the know convinced me that single-purpose solar installations are more efficient in reaching a financial profit (and presumably a net energy profit) than multi-purpose installations. All I’m saying is that that argument makes sense to me, and I’d have to see some numbers to convince me otherwise.

A. Siegel

There are many people “in the solar industry”.  Reality is, as with most business operations, there is a rather stove-piped analysis:  how much will it cost and what is the financial ROI within the deal.  With that perspective, doing a solar carport is idiocy because there are extra costs to put it up with basically identical electricity return. If you think about broader (holistic) ROIs, then the equation is different. Among other things, just like a roof, this is dual-use — so there is no ‘energy sprawl’ challenge of dedicated land to a solar installation.Here is an example of that broader thinking

When the company moved its headquarters from Westshore to the corner of Kennedy Avenue and Willow Street just west of downtown Tampa, one of the biggest employee beefs was the lack of covered parking. So McCree had carports built with roofs made of solar panels — 400 of them.

Thus, with carports, the firm is resolving an employee grievance: we want to part our cars in the shade. With solar carports, happier (and thus more likely to stay?) employees.Solar Carport at Cal Expo

On that sunny day in May, First Housing was waiting for approval from Tampa Electric for phase two of the project. McCree anticipated that when the carport panels went on line, the energy tab for his three-story, 17,000-square-foot HQ would fall from $3,000 to $400 a month.

And, there is the question of heat island impact, reduced gasoline usage, etc …If stovepiping the analysis within EROEI (energy return on energy invested) or stovepiping the financials solely on direct transactional value streams, then car ports are far down the list. If thinking more broadly, they are legitimately ‘in the mix’ a lot of the time.

If we are to look solely at the EROEI, then building a solar carport is not sensible.

However, we should look at situations not as things but as systems.

Solar carports have lots of payoffs beyond electricity … if we calculate things in stovepipes, then the system’s true value streams aren’t part of the decision making.


This was originally posted on 25 Sept 2014 but was lost due to problems with the host service (Bluehost) and never restored by them in its original version (despite numerous requests for help, customer service that went mainly unresponded to).  Republishing prompted by this Washington Post story.   A story from back in 2007 on a California solar carport.

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Tags: Energy