Gas Storage Heating
These systems store heated water at a constant temperature in an insulated tank, ready for use. The water is reheated by a gas flame when the temperature falls below the thermostat setting. Internal and external models are available. Internal models require a flue. These systems are rated for their energy efficiency with an energy star rating system. The more stars the more energy efficient. Their storage capacity and recovery rate determines how much hot water they can deliver. Because gas hot water systems heat much faster than electric systems, they usually require a smaller tank to produce the same amount of hot water per hour.

Gas Continuous Flow Systems
Continuous flow or instantaneous hot water units as they are sometimes referred, heat water as required, so they never run out. They are a sensible method of water heating, since you only pay to heat the water you use. These units are much smaller in size than storage systems plus they can be installed externally or internally with a flue. They are rated by the volume of hot water they can produce per minute, which is