The most common way to heat water in the United States is with a tank-style water heater. Tank water heater units heat water even when not in use, to compensate for standby heat loss. Insulation between the storage tank and the outer jacket slows this heat loss, but cannot eliminate it entirely. To maintain a preset water temperature, the water heater must cycle on periodically, even when there is no demand for hot water.
Tank water heaters generally have about 70% usable capacity, meaning a typical 50-gallon tank has about 30-35 gallons of truly hot water in reserve for usage. If there is high demand over a short period - a family taking back-to-back showers in the morning or a vacation home packed with guests - the hot water can run out. When it does, homeowners have to wait for the water to get hot again.
Current gas hot water heaters contain special flammable vapor ignition resistant (FVIR) technology that prevents the ignition of flammable vapors, such as spilled gasoline, outside the unit. All gas hot water heaters sold since July 1, 2003, must have this FVIR technology.
If a remodeling budget is tight, tank water heaters will likely be the most affordable choice, since labor requirements are minimal. Installed costs are typically between $500 to $1,000.