Overall, the best window insulator kit is the Duck Brand Indoor Insulator Kit for its easy installation and its ability to be reused, which saves you money in both the short and long term.

Duck Brand Window Insulator Kit. See price on Amazon. See on Amazon. At $7 each, this insulator kit from Duck is a steal — especially considering that it has a 4.4-star rating.

Duck Brand Window Insulation Kit. ... In order to accommodate various window types, kits usually come in a variety of sizes (such as 3' x 5' and 4' x 6').

Duck Brand Indoor 5-Window Shrink Film Insulator Kit ($24.20) Amazon For $24.15, you can insulate up to five standard-sized (3 by 5 foot) windows for a drastic uptick in energy efficiency.