Hire roofer who knows solar or solar company who does roofing?

[jytte2]

Thank you for all the great suggestions and comments. I realize we need to do more research on types of flat roofing materials. There are better alternatives than torchdown, but some of the others, like TPO, are best without penetrations. EPDM is great, but it's much more expensive, especially in white. The standard black can get very hot where we are.

We've gotten a nice quote for a new torchdown flat roof with a 14 panel solar array, and I like having it on one bill for the tax credit. It's from a highly regarded local solar company. I've seen positive comments about them on this site.

We're thinking of having the panels tilted about 17 degrees from horizontal, as that seems to be optimal for summer. Our usage is highest then, and the low tilt would catch more of the early and late in the day rays. It seems that being able to adjust the tilt each season doesn't add that much more efficiency.

Will have to do some research about what azimuth is best for us. If google maps is correct as far as north at the top, putting the panels in rows would have them face south with maybe 15 degree off to the west. West is good for TOU rates, which I think we'll be forced onto, but it seems solar installers put panels in whatever way is easiest for them.

[littleharbor]

Not sure if Torchdown roofing has gone down in quality these days but I have done a fair amount of over the years and I have 20 year old roofs that are still in great, nearly pristine condition. Anything under an array should last considerably longer, IMHO.

[Ampster]

Thank you for all the great suggestions and comments. I realize we need to do more research on types of flat roofing materials. There are better alternatives than torchdown, but some of the others, like TPO, are best without penetrations. EPDM is great, but it's much more expensive, especially in white.
........... West is good for TOU rates, which I think we'll be forced onto, but it seems solar installers put panels in whatever way is easiest for them.

The HOA where I own a townhome recently replaced their former torch down roofs with TPO in white. To make the seams they use the same adhesive as they used for the boots that go around the vents. I had solar on that roof and they also used those same type of boots and the same 25 year guarantee applied. One of the things that made that installation less expensive is the roofer left the original hot mopped tar and gravel roof, and added 1" of high density foam so the R Value of the existing roof was increased. Because of the weight of new torchdown the old roof often has to be removed when replacing it with torchdown.
On a flat roof you should have some flexibility with the azimuth. Depending on your Power Compny and the regulations governing rates your strategy may be to favor some westerly azimuth. A good installer may be able to model that for your particular location.

[J.P.M.]

Thank you for all the great suggestions and comments. I realize we need to do more research on types of flat roofing materials. There are better alternatives than torchdown, but some of the others, like TPO, are best without penetrations. EPDM is great, but it's much more expensive, especially in white. The standard black can get very hot where we are.

We've gotten a nice quote for a new torchdown flat roof with a 14 panel solar array, and I like having it on one bill for the tax credit. It's from a highly regarded local solar company. I've seen positive comments about them on this site.

We're thinking of having the panels tilted about 17 degrees from horizontal, as that seems to be optimal for summer. Our usage is highest then, and the low tilt would catch more of the early and late in the day rays. It seems that being able to adjust the tilt each season doesn't add that much more efficiency.

Will have to do some research about what azimuth is best for us. If google maps is correct as far as north at the top, putting the panels in rows would have them face south with maybe 15 degree off to the west. West is good for TOU rates, which I think we'll be forced onto, but it seems solar installers put panels in whatever way is easiest for them.

After you get the roof decisions settled, chances are you'll have a fixed orientation system. Run PVWatts for a decent 1st approx. of best orientation for annual system output . Since most (but not all) NEM tariffs work on annual trueup, using the orientation that produces the best annual outcome is more important than simply worrying about maxing out summer production to cover higher summer bills. Check how your POCO operates to avoid screwing yourself with bad/incorrect assumptions. After that, there's the question of knowing that with most TOU billing schedules the best orientation for annual production is probably not the orientation that proiduces the most bill ($) offset.

From you latitude and other stuff you've written, it reads like you might be in my neighborhood (zip 92026). If so, and for most bill offset, you'll be on sch. DR-SES, or a similar rate and time schedule w/ a PV system and an EV. If so, and if you have some flexibility on orientation, a 17-20 degree tilt and a 180 deg. azimuth and not much shading will offset about $450/yr. per installed STC kW of PV. Same tilt but 200 - 210 deg. azimuth will offset about $460/yr. per installed STC kW of PV, so not much more. Self shading will reduce either amount. FYI, unshaded, a 20 deg. tilt and 270 deg. azimuth will offset ~ $420/yr. per installed STC kW of PV. So, and in spite of what some think, west facing arrays w/CA TOU rates and times is not as good as south facing - at least not around here. Optimum orientation for max. annual TOU bill offset of ~ $470/yr. per installed STC kW is very approx. 25-30 deg. tilt at ~ 220 deg. azimuth, but as you can see, it's not necessarily a deal killer for other "nearby" tilts and azimuths.

As for installers putting orientations where they want - well, who's the boss ? You need to understand that they may be hamstrung and perhaps limited by the site particulars that you may not understand. But, that's not to say that vendors don't like to make things easier for themselves if customer ignorance allows it. The best defense against that is to inform yourself of possibilities and limitations of what's possible for your application.