Seedling Heat Mat 10 x 20.75 in Waterproof Heat Mats for Seed Starting Seed Heating Mat for Seedling Germination,Hydroponic Plant. 【PORTABLE AND ENERGY EFFICIENT】: The size10 x 20.75 of plant heating pad is very suitable for standard plastic growing tray and it also runs at only 18 watts of power to help you save on electricity.