Common Questions to Ask a Contractor of Solar Installation

Q. What should I expect for a warranty of the PV system I purchase?

A. The various components of the PV system will each have their own warranties. Your PV installer should provide the detailed product warranties to you. Here are some of the common warranty features that you should look for:

Modules usually will have two types of warranties, which are as follow:

The first, and usually the shorter, is a material and workmanship warranty pertaining to the manufacturing of the module. For many modules this type of warranty is for a 10 year period. Some manufacturers offer a shorter period, a few offer a little more.

The second warranty is that the module will meet a specific performance level (under laboratory conditions) at a specific age. For most manufacturers this covers a period of 25 years, but the terms vary. Some manufacturers offer a stepped warranty, where the module should be at a particular level for so many years, then for the remainder of the warranty a lower level is allowed. Many manufacturers offer a linear warranty, in which the module performance is allowed to taper gradually over the life of the warranty. The linear warranty does not allow for as much “slack”, so if all other factors are equal, it would be advantageous to the system owner

Inverters warranties can vary quite a bit. Some manufacturers offer a fairly short warranty but then offer an optional extended warranties. One popular inverter comes with a 5 year warranty, but you can opt for a 20 year warranty package. Other inverters come with a stock warranty of up to 25 years.

Mounting Hardware, consisting of flashings, brackets, rails and bolts, vary a bit. Most rails and many flashings are made of anodized aluminum. A common warranty period for these would be 10 years, but the finish may only be covered by a 5 year warranty.

Labor warranties for the system are dependent on the PV installer. The minimum standard warranty would be 1 year. Some companies offer 5 or more year labor warranties.

Q. What are some of the best racking and mounting practices that my PV installer should use for my system?

A. A short list of things that should be taken into consideration is as follows:

Modules layout should avoid those areas of the roof where exposed the highest wind, if at all possible.

Mounting fasteners should penetrate into rafters, or into properly installed blocking between the rafters.

The quantity of mounting fastener is a factor in the systems resistance to wind. In the event of a wide rafter spacing, such as with some open beam structures, a third mounting rail can be added to the usual pair, thus providing more strength.

PV arrays are more securely held to the roof when all the rafters beneath the array are incorporated into the support system, yet it is not necessary to support each rail at every rafter. To maximize the system strength then, the rafters used are in a staggered pattern from rail to rail. Note that the rafters near the two ends of the rails will need to be used for both fastener patterns so that the rail cantilever can remain within the manufacturer’s specifications.