Tank vs. Tankless Water Heaters

Posted on: March 17, 2014

With the advent of new tankless water heaters, a debate has risen as to which is better:  On demand, or conventional storage models?  And it turns out that the answer, while clear cut to some homeowners, is not so to others.

What about Conventional Water Heaters?

If you’re debating between traditional and on demand for hot showers and washers in your St. Petersburg home, it’s best to know the pros and cons of both.

Insulated, storage tank models fill from the tap, raise the temperature with an internal electric or gas element, and keep it warm and ready for use.  But no insulation is perfect, and if your home isn’t frequently using exorbitant amounts of hot H2O ( e.g. – You wash your clothes in cold, the shower is only used once or twice a day, or your family tends more towards cool showers), then a lot of energy is going into maintaining all of that heat unnecessarily.

Another problem with tank models is their propensity to have the entire stockpile used up in cases such as when your family comes home from the beach and everyone needs a shower one after another.

These systems are also much cheaper than the alternative, but they have a shorter lifespan of about 10-15 years.

So what’s the breakdown?


  • Low upfront cost
  • No cap on output
  • ENERGY STAR® models available


  • Less energy efficient
  • 10-15 year lifetime
  • Can run out during high use

On Demand Water Heaters

If your home uses less than 41 gallons of hot water daily, then a tankless model could utilize energy up to 34% more efficiently than a standard one.  On demand units have no storage capacity and instead pass water over an electric or gas element, rapidly raising the temperature as it passes on its way to you.  This allows them to provide a limitless supply while avoiding standby energy losses.

If your St. Petersburg residence has a high demand, then tankless units lean more toward an energy efficiency of only 8-14%.  These models are also a big investment as they are apt to cost more than traditional models.  But with a longer lifespan of 20+ years, and easily accessible replacement parts, they have a tendency to pay themselves off in the long run.

Unfortunately on demand systems have a maximum flow rate of roughly 2-5 gallons per minute, which may not be enough for some high usage homes.  The fix to this is to have two units running in tandem, or have them installed at every faucet – This can actually boost your energy savings to upwards of 50%!

So here is the breakdown:


  • 20+ year lifetime
  • Easily repaired
  • ENERGY STAR® efficiency
  • Can save you up to $100 a year on your electric bill


  • More expensive upfront
  • Maximum flow rate of 2-5 gallons per minute
  • Less energy efficient for high usage homes

Ultimately, while tankless water heaters are overall more efficient, the decision on which type is best varies from home to home.  Study your usage, speak with an expert, and make an informed decision.


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