The incredibly efficient Eccotemp FVI-12 Natural Gas Tankless Water Heater uses an intense gas-fired flame to instantly heat water the moment it passes through the unit, so as long as you feed water in, hot water will come out! Comes ready to install. With the included horizontal vent kit, this Eccotemp FVI-12 Natural Gas Tankless Water Heater can be installed for indoor use right out of the box. Great for cabins and smaller homes, so you don't bust your budget for a hot shower! The Eccotemp FVI-12 Natural Gas Tankless Water Heater is a manual water heater. This means that any water temperature adjustments must be made at the face of the unit using the knobs for water flow and gas pressure. Mixing cold water at your output source is not recommended. Have questions? Contact support at 1-866-356-1992 or support@eccotemp.com.