TLEN works with whatever you select. Use the FILTER command or QSELECT before running TLEN to sum only red lines, or only lines on Layer "Electrical."

He thought of the anonymous downloader whose post had started all of this. Maybe they’d been careless, maybe malicious. The internet didn’t always sort motives cleanly. But for every unknown link promising a free fix, there would now be at least one clear voice saying, quietly: test first, verify often, and when in doubt, build it yourself.

: It typically supports lines, polylines, arcs, circles, splines, and ellipses. Measurement Accuracy

To ensure TlenLSP loads every time you open AutoCAD:

If your lines are 3D, some versions of TLEN calculate the true 3D length, while others calculate the 2D projection. Verify which version you have if working with 3D models.

How to Download and Use TLEN.lsp for AutoCAD: A Complete Guide