Rheem 4 Star Gas Water Heater Reduce your gas bills and your carbon footprint at the same time with a Rheem 4 Star 135L gas water heater. It’s an easy and more energy efficient replacement for most older gas water heaters. Rheem 4 Star 90L from $2000 Recommended for when there is low demend. Rheem 4 Star 135L from $2100 Recommended for most homes. Rheem 4 Star 170L From $2350 Recommended for homes with high hot water demand. All units are fully installed including removal of the old unit.