Read the owner’s manual for the electric baseboard heater. The safety instructions in the manual include the necessary distance between the heater and bottom of the curtains. This distance is often 12 inches.
Avoid floor length curtains because they'll touch the electric baseboard heaters. Choose curtains that end at the bottom of the sill or at the bottom of the window trim.
Measure the distance from the top of the curtains to a line 12 inches above the baseboard heater. Curtains that end above the baseboard heater may look awkward. To see what the curtains might look like, cut a wide piece of paper or fabric and hang it in the window. Observe the appearance of the curtains at varying lengths. Get curtains with that desired length.
Install the curtain rod in the desired location above the window. Hang the curtains and note the length. If the curtains are too long, closer to the electric baseboard heater than recommended, trim the bottom of the curtains and hem them, if possible.
Consider installing window shades or shutters. Correctly sized shades, blinds or shutters fit inside the window and don’t extend near the baseboard heater. Sometimes the appearance is more pleasing than a short curtain. Shades, blinds and shutters are available in many styles, materials and colors.