Solar Apartment Building?

[jerry1234]

I have an apartment building that needs a new roof. Well, the roof still works, but it's at least 17 years old. Time to replace before bad stuff starts happening. I was thinking of putting solar on that new roof. It's a 3 story building with a tar & gravel rooftop. The main power consumption of this building is not electricity ( which only runs exterior lights and a couple washing machines ) but GAS. We're running $300 to $500/month in gas, because we have common water heaters. I was thinking maybe a set of water heating panels to preheat for our water heaters. This would not only save on gas, but also increase the life of the heaters - because they would be heating less. That's a big deal, because these commercial high-recovery heaters are VERY expensive.

Does this sound practical? Are there contractors out there who specialize in such things? I know it's a slam dunk these days to find PV contractors - a lot of activity and competition in that space - but the electric bill for this property is only about $50/month.

[peakbagger]

It is very dependent on where you are in the country and what local and state incentives are available. If the incentives are right in your area a developer may pay to locate PV on your roof. Best thing to do is check out the DSIREUSA dot ORG website and see what incentives may apply. If you are in the south hot water panels may make sense but the current approach to water heating is heat pump hot water heaters with extra PV panels to cover the load in place of flat panel solar collectors due to the high initial cost of the flat panel installation. The trade off with heat pump hot water heaters is they pull heat from the space they are located in and that space needs to be above 45 degrees. If you have a hot mechanical room, its great place for them, if you need to heat the room then its not so good of an idea.

[jerry1234]

This is in the SF bay area. We have a very mild marine climate here. Doesn't get very hot in the summer, doesn't get cold in the winter. Almost never freezes, especially at low elevations.
I was thinking of the roof-rental option for another complex I have - in Fresno, CA. Different weather in Fresno. Tremendously hot summers. There I have 7 buildings with a
lot of nice south-facing roof area.

[J.P.M.]

Jerry: At this time, and as Peakbagger writes, the PV/heat pump combination option is probably more practical than the solar thermal alone option. The solar thermal option will take more maint. with fewer knowledgeable people to provide that service, and the PITA factor will probably be less w/PV, as well as some likely lower initial cost w/ the PV/heat pump option.


Depending on the building(s) and current plumbing/arrangements/etc., there are also other options such as each tenant having a heat pump water heater and a grid tied PV array. Lots of other options that may be good for both owner and tenant.

In either or any solar option, if your roofs are horizontal, expect to be placing any solar devices in an off horizontal orientation at a tilt of approx. the local latitude (say 40-45 deg. or so), facing mostly south. On a flat, horizontal roof, that will require a sawtooth arrangement if the array configuration requires more that one row of panels. As a SWAG for talking purposes only, expect the pitch (distance between rows) to be something like 2-3 times the panel height.