At the push of a button, Navien’s HotButton accessory activates the internal recirculation pump and gas-fired burner to heat up the water in the supply lines. This gives users hot water when they need it, saving water and money. It is now available as an add-on accessory for all NPE-A models (NPE-180A, NPE-210A, NPE-240A). It is compliant with California Title 24.