Number of Cells
Cellular shades can be categorized by the number of cells. Some are just one single cell deep.
Others are two cells or three cells deep. The greater number of cells, the more energy-efficient a shade is, because the air in each cell provides an insulating layer.
Size is measured in several dimensions for window blinds, but in comparing cellular shades, the relevant size is the width of the fabric part of the blinds when closed. This can vary from 3/8 inch up to 3/4 inch.
R-Value and Shading Coefficient
How much heat passes through the shades is measured by a number called the Shading Coefficient. A lower number means the shade blocks more heat.
R-Value is a rating of insulation value used by many building materials, not just window blinds. Not all window blinds have R-Value ratings, but cellular shades are among the most energy efficient window treatments.
A higher R-Value means the shade has a greater insulating factor.
There are several categories that describe the amount of light that comes through a window blind. Translucent blinds let in light but block images.
Room darkening or blackout shades block light from coming in, and are good for rooms where people need to sleep during the day.
Cellular shades come in both corded and cordless varieties. Cordless shades operate by grabbing the bottom and moving them up and down, without the need to deal with cords.
Another option is top-down-bottom-up, meaning that the blinds not only raise up to uncover the bottom part of the window, but they can be lowered from the top to uncover the top part of the window. This is especially good for double-hung windows that open from the top, but it can also provide privacy in the room while letting in some light if the windows are tall.