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Tankless – Sizing, Selection, etc.

/Tankless – Sizing, Selection, etc.
Tankless – Sizing, Selection, etc. 2018-08-13T09:22:33+00:00

Tankless hot water heaters come in several varieties, whole house, point-of-use, indoor, outdoor, and commercial.

Tankless hot water heaters are available in propane (LP), natural gas, or electric models.

Depending on your choice for a tankless hot water heater you may end up saving lots of money, you might loose money, and you might end up wasting a whole lot of water!

Tankless water heaters have pros and cons, just like everything else.  They can supply an endless supply of hot water, and can save energy. However, they are limited in the amount of hot water that can be produced at one time and they are more expensive to purchase than a conventional storage type water heater.

Tankless heaters take longer to deliver hot water to your fixtures and thus waste more water.

They also make it take longer for you to get your hot water, since they don’t start heating the water until you turn on the faucet. This problem can be solved by using a specialized pump, which in combination with the tankless unit can get your hot water to you at less than half the time it would take running the faucet full blast.

The tankless water heaters also cause an increase in water wastage since you have to let the water run longer to get your hot water. This problem is also solved when using the specialized pumping system. Water conservation is an important advantage to the pumping system.

Tankless water heater pumps

One such tankless water heater pumping system is the Chilipepper hot water pump.  With it you get both water conservation and the convenience benefits of faster hot water, and, an un-limited amount of  hot water. Tankless water heater pumps turn your water heater green!

Whole house or point of use?

Tankless water heaters come in a variety of sizes for different applications, such as a whole-house tankless water heater, a source for a remote bathroom or hot tub, or as a boiler to provide hot water for a home heating system.

Unlike a tank type unit, with an instantaneous model you will never run out.

A tankless water heater can also be used as a booster for dishwashers, washing machines, and as a backup for solar or wood-fired domestic systems.

You may install one centrally, or you can install one at the point of use, depending on the amount of hot water required. For example, you can use a small electric unit as a booster for a remote bathroom or laundry, or in the kitchen for cooking and instant coffee etc.

Gas units with a standing (constantly burning) pilot light, offset some of the savings achieved by the elimination of tank standby losses with the energy consumed by the pilot light. Moreover, much of the heat produced by the pilot light of a tank-type model heats the water in the tank, heat that is just lost with the instantaneous units.

An alternative to the standing pilot light is an intermittent ignition device. This resembles the spark ignition device on some gas kitchen ranges and ovens. You should check with the manufacturer for models that have this feature. More information about point of use tankless water heaters.

Point of use tankless water heaters

These small units are usually installed in a closet or underneath a sink, and are usually electric due to the difficulties involved with installing a flue.. If the unit is gas, a flue and gas piping will need to be installed which can cost a significant amount of money.  If electric you will probably need 220 volt service run to the location where the unit will be installed, which can also be some what expensive.

Gas-fired models have a higher gallons per minute output than electric models.

The largest gas models, which may provide all the needs of an entire household, are usually installed centrally. The flue required will be larger than that of a gas tank type model.

As with many tank type models, even the largest whole house models may not be able to supply enough for large simultaneous, multiple uses (i.e., showers and laundry).

Selecting the correct size is important

Large users such as the clothes washer and dishwasher, often need to be operated separately. Alternatively, separate units can be installed to meet the needs for individual loads, or two or more units can be connected in parallel for simultaneous demands. Some manufacturers claim that their product can match the performance of any 40 gallon (151 liter) tank type heater.

More about sizing tankless water heaters

Select a based on the maximum amount of hot water to meet your peak demand. Use the following assumptions on water flow for various appliances to find the size of unit that is right for your purposes:

Faucets: 0.75 gallons (2.84 liters) to 2.5 gallons (9.46 liters) per minute.

Low-flow showerheads: 1.2 gallons (4.54 liters) to 2 gallons (7.57 liters) per minute.

Older standard shower heads: 2.5 gallons (9.46 liters) to 3.5 gallons (13.25 liters) per minute.

Clothes washers and dishwashers: 1 gallon (3.79 liters) to 2 gallons (7.57 liters) per minute.


There is no question that instantaneous models save significant amounts of energy. Install a Chilipepper with your new unit and save time and water too!