How Much Solar Should I Install?

a0128958a0128958 Posts: 316Solar Expert ✭✭✭

I have a building in San Antonio, TX that I want to put solar on the roof top.  What I can't figure out is how much solar makes economic sense.

The building is a warehouse/distribution center, with plenty of additional office/administrative people.  Primary working hours are 5 AM to 7 PM, M-F.  The roof top is flat and is of a nature where the panels can be located optimally.  The building is large (400KSF) and single story, with nothing other than chiller units and warehouse exhaust vents on the roof.

Annual electricity consumption is 1,784,736 kWh, at a cost of $149,141 ($08.5/kWh).

How do I determine how much solar PV to put on the roof?

And should I instead contact someone who will lease a system to me at a fixed $/kWh charge?

Many thanks!

Best regards,



  • jonrjonr Posts: 1,105Solar Expert ✭✭✭✭
    I'd contact some local companies that are familiar with your local net metering rules.
  • BB.BB. Posts: 28,087Super Moderators, Administrators admin
    edited August 2016 #3
    Do not sign any contracts yet--Until you understand your local utility's rate plan(s) for your facility.

    In California, many larger commercial customers have rate plans that split the bill into (roughly) two parts. One is the per kWH charges, the other is a 15 minute peak power usage in the last 1 month to 1 year... And, if done correctly, about 1/2 the bill is reservation charges and the other half is per kWH charges. If your loads (and even solar array) is designed incorrectly, it is possible to end up with higher bills than lower bills (this happened to a few school districts in California where their very high summer power solar generation raised their reservation charges for peak power usage/generation).

    The other big issue is you are on the trailing edge of "peak solar"--Government regulations and subsidies that are now being phased out in some areas (Nevada and Hawaii, for example, have practically killed any new Grid Tied solar installations). It is possible that your utility may not support GT solar, and/or, you may have limited "Grandfathered Rights" to your rate plan (mine was 10 years, and is now slowly being changed to make my GT solar installation save less money).

    For a larger installation, you may need to hire a local electrical engineer to review your electrical usage and power bill and see what works best for your needs.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490mike95490 Posts: 7,970Solar Expert ✭✭✭✭
    A lease just means someone else gets most of the discounts and tax breaks
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
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  • GreenPowerManiacGreenPowerManiac Posts: 453Solar Expert ✭✭✭

    May wish to go Geothermal on that one.  Read this article when you get the chance.  Geo affords Heat/Cooling and energy reduction all in one.  

    If not, I'd suggest getting as many panels that will fit your establishment.
    Nature's Design & Green Energy on FaceBook : Stop by and "Like" us anytime.. Many up-to-date articles about Renewables every day.
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