Point Of Use Water Heater vs Tankless
point of use water heater vs tankless
When homeowners decide to use tankless water heaters they typically want to know whether they should use a whole house tankless water heater or several point of use units, or zone units. The correct answer lies within the needs of each house and the family that occupies it. Let’s start with the structure of the home, first.
Existing Homes: Depending on the age and construction type of the house, existing homes can be very difficult to retrofit with electric lines, and running new gas lines is virtually out of the question. Therefore, in an existing home a whole house tankless water heater is usually the best way to go. Another newer option is to install an outside tankless heater. The new Bosch Anti-Freeze system makes outside installation a good option for many applications.
New Construction: If you are building a new home then running electrical lines to each application point for hot water is relatively simple, since the bathrooms, kitchen, laundry room and utility room will already be wired. In addition, if you choose to use gas-fired tankless water heaters rather than electrical, running gas line to each unit is also much easier.
Another clue for new construction is the way the home is constructed. Remember that if you use a whole house tankless water heater then water will be heated at one location and dispersed through pipes to each point of use. Once you turn off the hot water tap there will be hot water still in the line, and that water will immediately begin to cool, which produces inefficiencies and waste. If the home you are building is spacious and spread out this will lead to energy loss. And if you use metered water, you’ll watch your utility bill increase every time you turn on the tap and wait for the water to get warm.
For these reasons many new home projects employ several point of use tankless water heaters. The upfront cost is greater but the energy savings is increased substantially. For example, if your home requires 7 gallons per minute capacity of hot water it will cost less to purchase one unit capable of producing 7 g.p.m., and there are many that do, than it will be to purchase 1 unit with 3 g.p.m. capacity and 2 units with 2 g.p.m. capacity to serve various zones of the home.
However, over time the 3 separate units will use less energy combined than will the one large unit, in most homes anyway. By the way, the need for your particular home is determined by adding up the number of hot water points and their water needs, while also taking into consideration how many points are likely to be in use at any one time. A few examples: bathroom sink, .5-1.0 g.p.m; kitchen sink, 1.0-1.5 g.p.m; shower 1.5-3.0 g.p.m.; and dishwasher 1.0-3.0 g.p.m. Learn how to create a usage audit of your home to help you determine which type of tankless water heater is best for you.
That leads to the second major criterion, the water usage patterns within your family. Home energy experts suggest a whole house tankless water heater when the hot water taps throughout the home are used regularly during the day. Several people getting ready for work or school in the morning use plenty of hot water. A parent at home during the day caring for young children while cooking or doing laundry will use significant hot water. Everyone home in the evening or on weekends will also lead to greater use. A whole house unit is the right choice in these settings.
On the other hand, if certain areas of the home are used infrequently or sporadically – a utility/laundry room that only sees action on the weekend, a guest bathroom and few guests, a jetted tub in the master suite or on the deck that is more of a cold-weather toy – these scenarios make point of use models more cost effective. Break up the home into zones and service the kitchen and guest bath, for example with a 3.0-5.0 g.p.m. model, service the master suite with its own 3.0-4.0 g.p.m. unit and meet the needs of the main bath and laundry area with a 3.0-4.5 g.p.m. unit, as one possible arrangement. The layout of your home will affect the way you select zones.
It should be noted that if you choose to fuel your tankless water heater(s) with gas rather than electricity because of the lower relative cost of gas/propane then a whole house unit makes better sense. It will be more efficient and will save you the expense and hassle of trying to supply gas to 2 or 3 separate locations in the home.