Coolstar water coolers use a hermetically sealed compressor of high efficiency. An oversized condenser coil coupled with liberal sideways ventilation makes them highly energy efficient and gives longer life to the compressor. Hence the water coolers can be installed close to the wall saving space. The closed cell expanded polystyrene insulation protects the water cooler from breeding insects and bacteria. This is due to the non porous insulation unlike the conventional systems where the glass wool, being porous, breeds insects and bacteria.