Plan a budget for your solar screen purchase. This will help determine which type of screen material to go with if you have a number of options.
Clean off the window where you wish to install the solar screen. Use a bucket of soapy water and a brush to remove any leaves, twigs, dirt, mud or other debris around the corners and sills of the windows. This will allow you to have a more accurate measurement.
Measure both the width and height of the outside of the window. Measure from the inside of the window frame to the opposite side of the interior window frame. Write these measurements down.
Pick the color and shade density of the solar window screen. Although solar screens don't come in a wide variety of colors, you may be able to find one that fits in with your decor. Some popular color choices are chocolate, stucco, charcoal, gray and beige.
Check online or in your phone book for solar screen vendors near you. When consulting with a salesperson, have your measurements, color choice and budget handy. If you are a DIYer, you can look into purchasing a solar screen kit so you can assemble it yourself. This process takes longer than having a professional install the screen, but can save you money in the long run.