It makes complete sense...
Having worked in industrial facilities where the roofs are always changing, as a vocal proponent of renewable solar energy, I'd been asked many times if it would be valuable to put solar panels on the roof of the factories I worked at. I kind-of laughed.
Industrial electric demands can be extremely high, running and cooling powerful machines inside. Industrial roof-lines are always changing to install new equipment like scrubbers, VOC systems, reoriented chilled & heating water systems, air handlers and condensing units to fit the needs of what is going on inside the building.
But on a relatively static roof as in big-box stores, malls, homes, and other commercial buildings, solar installations make complete sense.
The only question I ask - because the highest cost is the new infrastructure including the conduit, roof supports, and the high voltage DC to lower voltage AC inverter - "Is the installation designed to be retrofit with much higher efficiency panels in the near future?"
Most solar panels sold today are about 14% efficient (140 Watts per meter). Some thin film products reach as high as 24% efficient in the lab. But likely very soon, lead-selenium quantum nano dot technology will reach the market with projected efficiencies of 40 to 50% and better yet, the nano antennae technology may extend efficiency to 80% or higher.
So for a big box store with 1,000 square meters of solar panels installed at 14% efficiency, they might produce about 140,000 Watts of power today, but might be able to hit 800,000 Watts of power not too long in the future (say 10 years from now.) If cleaned regularly, those 14% efficient panels can produce electricity for 25 to 100 years. At the potentially high output from upgrading to the latest high efficiency panels some time down the road, it may be very valuable to install everything to upgrade up-front. The the old panels will likely be valuable for resale to other uses, other installations, paying part of the upgrade costs.
Something that has always irritated me was that solar panel manufactures are not required by law to rate their panels on a "Watts per square meter" basis as "full assemblies with a 1,000 Watt per square meter source". (The "average" sunlight intensity across the US is often cited as 1,000 Watts per square meter, though it is higher in many locations at noon on a cloudless summer day.) Such ratings would offer consumers a better feel for how much energy they can produce and how much roof they need.
