Without a pool cover, the cost of operating a Heat Pump or Gas Heater is doubled, and a Solar Heater's effectiveness is decreased.  For convenience a roller may be added to ease placement and removal of the cover.  If a pool cover is not to be used, the size of the heater must be increased by 75% - 100%. Pool covers range in cost from $60 to $130 for residential pools; rollers start at $185.