The Expanse Water Heater is for the caravanning industry for under-floor installs. It provides the possibility to work off a blank canvas when designing the interior layout of the vehicle. As a standalone dual-fuel water heater independent provision of hot water is possible without compromising space heating comfort. The in house developed burner and heat transfer devices provide unrivalled speed of heat into the water supplying hot water for showers at comfortable length. Achieved through high efficient gas combustion and ideal positioning of the electrical elements combined with low standby energy consumption these features ensure that the Expanse provides the comfort expected at the lowest cost of heat and least environmental impact. The external mounting position allows the flue gas ducting to be routed safely without having to penetrate the vehicles walls thus leaving a clean overall appearance of the vehicle. Access to all maintainable components is from one side to offer maximum installation flexibility. All components exposed to the elements are from durable materials. The Expanses modular design ensures a high rate of maintainability and ease of end of life recycling.