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I'm looking for advice on choosing from two solar panel proposals. I have a historic landmark brownstone in Brooklyn with a flat roof and am looking for the most power that I can fit into the roof while still meeting all the fire and landmark requirements.

One proposal is a 9kw system with 25 SunPower X panels, mixed orientation and 2 degree pitch.

Sunpower

The other proposal is a 6kw system with 17 LG 360W panels with a 25 degree tilt.

LG 360 Plan

They both have a similar price after tax credits and rebates, but the LG seller tells me that having so many panels on a Brooklyn roof like that will require delays in approvals and that a mixed orientation is not advisable and that the tilt angle is also not advisable.

If I were to look at purely an economic decision 9kw for the same money as 6kw makes the 9kw system an easy decision.

Are the warnings about the mixed orientation, tilt or the placement of so many panels a merited criticism? Which system/provider should I go with in this case? Are there hidden costs with going with SunPower vs LG360?

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  • Interesting question. I wonder what the argument against mixed orientation is? Also, the two designs seem to have different paths for access - I assume both designers know the rules and they are both valid?
    – JPhi1618
    Mar 20, 2019 at 14:52
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    Is this for an off-grid emergency power system, or will it strictly be grid tied/reduce your electric bill type stuff?
    – Harper - Reinstate Monica
    Mar 20, 2019 at 20:58
  • On grid system only
    – MonkeyBonkey
    Mar 21, 2019 at 12:53

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Ask them for a total annual power generation estimate using NREL PVwatts. What you want to see is how many kW-hr of power each system should generate in a year under typical weather conditions.

The two systems are going to perform drastically different given their orientation and inverter arrangements. Depending on how the panels are strung together this could be a very large effect. Comparing the total # of kW is not sufficient.

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