What you need to know about tankless water heaters

If you’re thinking about replacing your water heater, a tankless model can be a great option, but it’s important to examine both the benefits and limitations before buying.

Tankless Water Heater

Tankless water heaters are significantly different from conventional water heaters and have some advantages over those with storage tanks.

  • If space is a consideration, a tankless water heater may be for you. They require much less space than a conventional water heater. The storage tank of a conventional system has a large footprint; tankless water heaters have a compact design, are wall-mounted and can be installed almost anywhere.
  • Tankless water heaters are typically more energy-efficient than their conventional counterparts because they only heat water as it’s needed. A conventional water heater stores water which must constantly be reheated as it cools. By switching to a tankless unit you could potentially save 30-40 percent a year on your water heating costs.
  • Going tankless means you’ll never run out of hot water. The output of a conventional system is limited to the size of the storage tank. Since tankless models heat water on demand, you will have an endless supply.
  • You may be entitled to a rebate if you’re replacing a conventional water heater with a tankless unit.

Tankless water heaters do have their limitations, though.

  • They aren’t recommended for areas with very hard water, because they’re more prone to build up water scale than conventional water heaters.
  • Be prepared for a short delay between turning on the tap and having hot water. Tankless systems require a minimum flow rate to operate, usually .6 gallons per minute. This means if you’re switching from a conventional storage-type water heater you’ll have to run the tap longer than you used to for tasks that require small amounts of hot water, like rinsing dishes or shaving.
  • Be sure that a tankless hot water system can meet your output needs. The water heater’s ability to provide that endless supply of hot water could be impacted by the temperature of the incoming water. The hot water supply capacities for most tankless models are based on an incoming water temperature of 70° F. If the incoming water is cooler – as it is here in Ontario – that can have an effect on the amount of hot water the heater can supply, so take this into account.
  • Tankless hot water systems require a higher gas flow rate than conventional water heaters, so you may need to upgrade your natural gas pipes. This is a potential expense you should bear in mind before making the move to a tankless hot water heater.


If you have questions or need help deciding if a tankless hot water heater is right for you, give our experts a call at 1-800-266-3939. An Energy Management Consultant will be happy to take a look at your current setup and advise you on the type of hot water system best suited for your needs.

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4 Responses to “What you need to know about tankless water heaters”

  1. Gina says:

    Is it absolutely necessary to flush the tankless yearly with vinegar and water or is there another way to clean it?
    If flushing is necessary in Toronto, how should it be done by the homeowner?

    • Dave says:

      Hi Gina,

      It is recommended by the manufacture that the unit be inspected and maintained annually. All repairs and maintenance must be completed by a licensed professional. The manufacturer (Rinnai) recommends vinegar as the flush solution, however there are products on the market such as Flush-Aide which are a one-time alternate flush solution option.

      If you install this water heater in an area that is known to have hard water 12 gpg or higher, the water must be treated. I believe the water hardness for Toronto is rated @ 7 gpg, for more certainty you should check directly with your local municipality.

      The units we supply from Rinnai have built in error codes and diagnostics that determine when it’s time to flush the heat exchanger. Flushing the heat exchanger can NOT be performed by the home owner unless the home owner holds a valid TSSA issued G2 gas certificate for Ontario.

      If you rent your tankless water heater from Direct Energy, all required service, repair and maintenance including flushing is covered under the rental program. Complete piece of mind provided under our same day service promise.

  2. Terry says:

    Do tankless water heaters work on stand alone propane fuel systems? I am thinking about one for a house which does not have residential natural gas.

    • Dave says:

      Hi Terry,

      I’m sorry but I don’t know if there is. I’m wondering if your propane supplier could answer that.

      Sorry we couldn’t be more help.


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