The majority of heat lost is through the cover, and not all covers are made the same.
Higher Density Styrofoam = Less Space for Absorption
Covers are tapered from the centre to edge, and can determine how well it will stand up to elemental pressures. While there are cost effective covers available, we often recommend spending the little bit extra to get a minimum of 4”-3” taper, it can increase the life span of your cover by quite a few years. 3”-2” (or less) covers tend to be flimsy and have the potential to crack or break under the weight of water or a heavy snowfall just after 1-2 years. A mid range cover will still need to be replaced around every 5 years. The absorption of condensation will make it heavy and difficult to remove as time goes on, as well as decreasing its effectiveness in keeping heat inside your hot tub.