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I have a house under construction, and the electricians have installed a 1" conduit from the attic to the main panel.

I have also gotten 5 quotes to install a Solar PV system around 9kW. I can purchase the same components (panels, string inverter, racking) for about 1/3 of the cost in the quotes.

My Questions:

  • Has anyone installed panels on a roof their-selves? Was it challenging
  • Would I hire a roofer to make the penetration and install the racking?
  • What trade would install panels on the roof?
  • Any difficulties involved I should be aware of?

I am very comfortable with home circuits, breaker-box, panels and such.

Thank you

  • who is the manufacturer of these less expensive panels, inverter, etc.? I am not doubting the possibility of beating the installers' costs by a wide margin, but I am curious (and also want to make sure we're not comparing to the complete junk on AliExpress/Amazon Marketplace/eBay.) – Harper Jul 14 at 17:03
  • Unfortunately, this is far to amorphous and broad a question for our Q&A format. – Daniel Griscom Jul 14 at 18:18
  • Is your goal to have a system that's purely grid-tied? Also, have you accounted for the NEC 2017 rapid shutdown requirements? (They practically require module-level power electronics, either in the form of dedicated rapid shutdown hardware (IMO FireRaptor or the Tigo shutdown-only stuff), solar optimizers (Tigo or SolarEdge), or microinverters instead of string inverters). – ThreePhaseEel Jul 14 at 22:31
  • SolarEdge inverters, and Qcells or the like panels. – Britt Jul 15 at 1:51
  • @Britt -- I take it you're thinking purely in grid-tie terms then, and not in terms of having storage or standby power capability? – ThreePhaseEel Jul 17 at 22:48
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Roofs are difficult places to install solar panels, so they're not my first choice.* There are several issues when you put a panel on a roof, and they have to do with fireman access to the roof.

You need to arrange aisle-ways between rows of panels so that firemen can reach the roof. This will effectively break the solar panels into sections.

You need rapid shutdown: an ability to de-energize the solar panels from a switch on the side of the building.

  • If you want to pump up a series string to multi-hundred volts, to reduce voltage drop, then you need a set of relays that will disconnect each section of panel such that the inter-section voltage is less than 30 volts.
  • Voltage within each section must be less than 80 volts.

Your PV array also must be listed or labeled for rapid shutdown, i.e. made for that.

One way around the rapid shutdown issue is run the array at less than 30 volts. This would require flowing 300 amps in total. So you'd want something to carry that kind of current. The obvious thing to me would be aluminum panel racking.


As far as roofs, you haven't discussed whether you are building a generic common roof just like every roof in the past 50 years, or whether you are engineering the roof specifically to support solar panels. For instance I would design it with parapets to attach solar panel mountings to, without necessitating roof penetrations. This would also reduce the roof to a series of shallow trenches, which would lend themselves to rubber roofing material, making it easy to maintain in segments.

Roof penetrations are generally bad, and create opportunities for leaks. So you should avoid them whenever possible. Despite the sunk cost of having the electrician run the conduit to the attic, I would not follow through and come through the roof; I'd route over the eaves and enter the house beneath an eave.

Given all these roof hassles, unless you have factored for all the above considerations, you may want to find a place other than the roof. Surely you have a driveway, parking spot or patio you'd like shaded?

If you're committed to doing a plain old roof, then have roofers do it. Then have a solar installation specialist install the solar panels.


Lastly, be careful about service panel sizing. Sizing is not an issue if your panel's bus ampacity is large enough to handle your main breaker trip and also your solar system output (9kw = 40A).

Speaking of sizing, panel space becomes a factor especially if you start doing power-down recovery, Tesla Powerwalls and the like. Most builder specify a service panel in the 20-30 space range. Tell him you want a 40 or 42 space panel. It also helps to use a panel type that supports a wide variety of additional features - Square D QO or Siemens come to mind.


* Actually, my preferred location is Antelope Valley. It's near L.A. which has a huge commitment to solar, and huge peak demand with little alternative, so they pay top dollar for solar peaking power. Take that money home and buy any old local power.

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I integrated the solar panels into the roof, some interesting points:

  1. The angle is 70 degrees (steep to maximise winter output) - snow falls off and rain washes off dust so never needed cleaning in 15 years.

  2. The panels are the waterproof covering so saving the cost of the tiles beneath.

  3. The array is in series to give about 380V DC, this minimises the losses , as well as a cable over-specified to keep losses to a minimum.

  4. The annual output exceeds the predicted (or simulated) output by about 15% - due to the winter sun being reflected off the snow onto the panels - remember the steep angle...

  5. The annual production exceeds the annual use - but that is what it was designed to do.

So, work out what you want to achieve and make sure you account for all use...

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