Somfy ST40 vs LT50: Which Motor Is Right for Your Shades?

It depends on the shade size. For standard-width windows (up to about 72"), the ST40 can handle most blackout fabrics. However, for oversized blackout shades or heavy layered fabrics, the LT50's higher torque output is recommended to prevent motor strain and premature wear.

Installing an undersized motor leads to premature wear, inconsistent limit settings, grinding noise, shade stopping midway, and eventual motor burnout. We regularly service systems where an ST40 was installed where an LT50 was needed. Motor replacement and proper specification prevent recurring failures.

In many cases, yes — but it depends on the existing tube size, bracket compatibility, wiring configuration, and space inside the headrail. A professional assessment determines whether a direct swap is possible or if additional modifications are needed. We provide on-site diagnostics for motor upgrade projects.

The motor model is typically printed on the motor label inside the shade tube or headrail. If you can't access it, our technicians can identify the motor during a service call and recommend whether it's appropriately sized for your application.

Yes. Both the ST40 and LT50 are available in RTS (Radio Technology Somfy) and hardwired versions. They integrate with Lutron, Control4, Savant, and other smart platforms. The key is ensuring the motor version matches your system architecture.