What is a hybrid water heater?
A hybrid hot water heater is a hot water system that uses a combination of both an instantaneous hot water unit and a small storage tank to overcome some of the shortcomings of both tank storage and tankless hot water systems.
Many manufacturers also refer to gas or electric boosted solar hot water systems as hybrid hot water systems too, and those systems are more common than tank/tankless hybrid systems. Obviously it’s important to be very clear about which type of ‘hybrid’ system you are referring to!
How hybrid water heaters work
Hybrid hot water heaters are a combination of the storage tank and tankless varieties of systems, and use the best aspects of both types to produce a very efficient hot water unit. Storage tank systems can run out of hot water at any time, while tankless hot water heaters require some ramp up time during which water is wasted, and in most cases they perform inconsistently when more than one or two water outlets are being used.
Hybrid systems have a small storage tank which acts as a buffer against high water demand. This ensures that consistent pressure and temperature are maintained when multiple outlets are being used, but the system otherwise operates the same way as a tankless water heater. Because the tank is small, the cold water pumped into it heats up much faster than a normal storage tank, so that continuous flow can be sustained. Solar versions will require collectors on the roof but will often utilise a gas or electric booster.
Types of hybrid hot water system
Hybrid tank/tankless hot water systems are available as solar, gas or electric models. Fuel and environmental efficiency are generally better with a solar/gas powered version. As they are a recent development on the market there isn’t the huge range that you might find with pure solar, gas or electric systems, but expect this to change in coming years.
Hybrid systems are easy to install, incredibly efficient and offer the benefits of both tank and tankless systems; consistent, instantaneous and continuous hot water. It is possible to combine this style of water heater with evacuated tube solar to radically improve an already efficient system even further, but you will need room for the collectors to capture sunlight. As with all new technology though, upfront costs are going to be a little prohibitive and repairs (if you need them) may also be steep.
Depending on the style of hybrid system you’re thinking of, you may need access to gas piping (also known as 'gas reticulation') and/or adequate space for solar collectors. Due to the design of these units many factors have been considered to make them as flexible as possible; the units are about 60% of the size of a regular storage tank and have a much lower heat output, meaning interior installation won’t require you to redesign your house.