top of page


Structural Letters & Electrical Stamps

Roof Letter & Pages Stamped

This cost effective, fundamental letter is what the majority of AHJs require. It states that a roof can handle the additional loads of the solar system, and includes design stamps.

Installation Letter & Pages Stamped

This letter includes the roof only letter, additional calculations to determine the attachment separation, as well as design stamps.

Installation Letter & Pages Stamped + Electrical Stamp

In addition to the installation letter, this service consists of a thorough review and stamp of the entire design, including electrical. The precise review and stamp of the electrical design is performed by an in-house licensed electrical engineer.


Artboard 34.jpg

Our benefits

Zero AHJ Rejection Guarantee

Solar Letters leverages Castillo Engineering’s experience since 1998, which has an industry leading 99.9% first time approval rating. If our letter receives an AHJ rejection, we will gladly issue you a full credit.

Fastest Turnaround Guarantee 

We pride ourselves on our advanced automation, as we know how important it is to receive your stamps within the hour. If you do not receive your letter by the next business day or less, you will receive a full credit. 

Lowest Price Guarantee

We will match or beat any documented competitor price. We also offer volume discounts through our Permit Partner Program.


Post-Installation Letter (PIL)

After the installation is complete, this letter verifies that site observations have been performed by an in-house engineer. It states that the system has been installed per the permitted plans.

Who we support

Small to mid-size residential installers

Large national residential installers

International design


AdobeStock_201160362 smaller.jpg

Get started with today!

CAD Design + Stamps

Through our proprietary CAD designs, we optimize installations while reducing cost. Our approach guarantees high accuracy and the lowest bill of materials. We also include PE stamping for free.

bottom of page