The best water heating option for a given household will depend on a number of factors, including
average daily hot water use (total gallons per day), hot water draw patterns (close together or spread out),
the hot water distribution system (compact or distributed), installation constraints (such as space,
electrical service, or venting accommodations), and fuel-type availability and cost.

The local water quality is one of the factors that contributes most significantly to the long-term performance and longevity of water heating equipment. Specifically, highly alkaline water will lead to the accumulation of scale, which will impact the efficiency of tankless and gas storage water heaters and can lead to decreased equipment life. Conversely, soft water increases the risk of corrosion, which can decrease equipment life by more than half if not properly mitigated. Increasing the lifetime of water heaters can improve the cost-effectiveness and increase the amount of savings achieved by an efficient water heater investment. Based on the specific water quality characteristics in a given location, different water heater design parameters and maintenance requirements can be applied to mitigate scale accumulation and corrosion in hard and soft waters, respectively