Rooftop or carport solar? How to choose the right option for your business

💰 For most, it's about price

Carport systems, also known as ‘canopy’ solar systems, are significantly more expensive than rooftop or ground mount systems. How much more expensive, however, is harder to find. On-the-ground data is scarce, as national organizations that track solar costs (e.g. NREL) don’t split out carport solar costs explicitly.

Fortunately, as a clean energy marketplace for commercial and industrial (C&I) buildings, Station A has unique insight into this market. Through our marketplace data, we see average bids for carport systems come in around $3.24/W DC for systems sized 200-800 kW. Meanwhile, rooftop systems average around $1.84/W DC for a similar size of 200 kW and C&I ground mount systems of size 500 kW average around $1.94/W DC.

Thus, carport systems on average conservatively cost at least 76% more than rooftop systems, and around 67% more than ground mount systems.

Some notes on how we got these numbers:

• The NREL data we used for rooftop solar pricing references 200 kW systems, which is the lower bound of the system size we referenced for carport pricing. So, the average rooftop system price cited here is on the higher end of what you would likely pay. Thus the 76% price difference between a carport and rooftop system would likely go up as you size up the system and benefit from scale. 
• Ground mount costs from NREL are right in the middle of the carport range at 500 kW, and thus a good comparison point.
• Larger systems will benefit from economies of scale, and would be less expensive, a trend that we see holds both for carport and rooftop systems.
• We’re using pre-incentive cost numbers for ease of comparison. With the addition of the ITC, ‘energy community’ tax credits, domestic production bonuses and more, we’ve seen systems discounted up to 70% from these values. Station A offers a free building analysis that takes tax incentives into account, request your analysis here.
• Prices are in 2021 USD.

🚗 Carport solar systems make sense in a few conditions

Even with the higher costs compared to rooftop and ground mount systems, sometimes carport solar still can make sense for your building — let’s talk about when that would be the case.

There’s limited onsite space available, and energy costs are high

In other words, carport solar may make sense if:

1. There's not adequate roof or ground space to place enough solar panels to cover your building’s load, and
2. Your building has a high enough energy cost to cover the higher cost of carport solar.

Commercial and industrial sector solar systems generally “pencil out” in areas with high electricity costs, good incentives, and decent sunlight. Surprisingly, sunlight is the least important of the three!

C&I solar systems are generally sized to earn the most money possible by matching the energy use of the building. Too small, and the owner misses out on savings compared to utility rates and doesn’t achieve economies of scale. Too large, and the electricity produced above and beyond the load of the building earns little to no revenue. Of course, incentives include policies like Net Metering — in California, with the passage of NEM 3.0, many projects which would have been economically viable at a larger size now must be downsized to ensure the maximum return.

For some use cases (e.g. unrefrigerated warehouses), the roof space and open ground space can host enough solar to more than cover building electricity load. However, this isn’t always the case. For instance, perhaps the roof contains other equipment, or the available ground space is being reserved for future development. For properties in which there is less available roof or ground space than which is necessary to offset load, carport systems are a good option to supplement.

The roof is not close to replacement, or cannot support solar

One great feature of rooftop solar is that sometimes an owner can take the opportunity to refresh their roof at the same time as installing the solar. This can be cheaper than independently replacing a roof and independently adding solar. Thus an owner may wait until a roof is nearing replacement before opting for a rooftop system. If a roof needs to be replaced just to accommodate solar, the economics may not work out. In this case, it’s possible that carport systems make more sense.

A property may also have structural constraints or poor design that could restrict the amount of supportable rooftop solar, or even prohibit any solar development. In this case, ground mount or carport solar is the only option, short of rebuilding the whole facility.

We have heard of cases where buyers incorporated roofing improvement costs into the total cost of the project applicable for the ITC. This is possible when the roof update is a requirement to achieve the maximum power generation of the system being installed.

“PR Value” and public visibility are inherently important

A great feature of carport solar systems is their visibility. While building owners can still highlight rooftop systems via roof images in promotional materials, the day-to-day visibility of carport solar can’t be beaten.

Every time someone drives past a building with carport solar, they can see the commitment to sustainability; no advertising or drone photos of the roof are necessary. It’s also an added boost for employees coming into work - they can see every day that their employer is climate and energy smart. This credibility and visibility may be worth the extra cost of carport solar, and we’ve seen buyers on our platform interested in a carport system simply for this value.

Shading the parking lot is highly valuable

Additionally, some building owners may see the shading benefits for their parking lot as worth the extra expense (often in combination with PR value).

Especially in hot climates, the amenity value of shade from the carports may exceed the extra cost of the systems compared to rooftop or ground mount systems. The shade is a welcome benefit for anyone visiting the facility, including both customers and employees. The amenity value of this thoughtfulness may translate to a higher NOI for the facility or longer or more repeat visits from prospective customers.

💬 In summary

When adding solar to your property it’s most economical to start with rooftop or ground mount solar, only expanding to carport solar if those two options can’t offset your full load or when the PR value and amenity value of shading your parking lot exceed that extra cost of the system.

If you need help evaluating your buildings for solar, using only an address, Station A can quickly estimate the economics of a solar project at that location through our Free Portfolio Report. Refine your estimates with your actuals and work with our team of advisors to determine your solar opportunities.