This is Lesson 8 of our informal online course: Home Energy 101All lessons by Philip Drader, Home Energy Coach.

There are lots of uses for hot water in the home. Together, they add up to make your hot water heater the second biggest user of power in the home. In 2010, it was responsible for 17% of the total residential energy use in Canada.

How we use hot water

  • 34% is used by faucets for for handwashing, dishes, and food prep
  • 25% is used by showers
  • 17% is used by clothes washers
  • 15% is used by baths
  • 4% is used by dishwashers
  • 5% is lost by leaks

Source: NRCan, Water Heater Guide, p. 35 (PDF)

How to reduce hot water use

Reducing water use is a good first step. It is fairly simple, as well as inexpensive, by doing things such as:

  • putting low-flow aerators in your faucets
  • installing a high efficiency showerhead and using a shower-timer
  • shifting to showers from baths
Wash clothes with cold water

Unless you have diapers, heavily soiled clothes, or are washing sheets after having had an illness, today’s detergents will work perfectly well in cold water. Consumer’s Reports does regular testing of the common detergents brands in the market to see which is most effective if you have any doubts about their cold water efficacy. Learn more about the benefits of washing clothes in cold water.

Dishwashers use less hot water than doing them by hand

The energy efficiency numbers on dishwashers may surprise some people, so here is a visual of how much water a newer, ENERGY STAR model uses. The maximum L/wash is 13.23 with a number of options below 10L/cycle while a typical kitchen sink holds 56 – 75 litres.

Fix leaks!

A quick word about leaks- they don’t fix themselves, and they don’t get better. If you’re going to fix it eventually (which you’ll need to do), then you may as well fix it now (or get someone to fix it). Save yourself the cost of the hot water that you’re not using.

How to make hot-water more efficient

Now that we’ve covered reducing wasted water, let’s talk about making hot-water more efficient.

If you have a pilot light or an induced draft water heater (photo), you can increase the efficiency by at least 10% by going to a newer ENERGY STAR water heater.

Unfortunately, with the current pricing of water heaters in Ontario, you have to use a LOT of hot water to make that an economically viable choice, and if you did some of the things above, it’s not worthwhile to make the switch until your current water heater conks out. If you use $150 of natural gas per month in the summertime, then it’s worthwhile to switch now.

Consider an air source heat pump

There is a huge potential for improvement in the market in the realm of air source heat pump water heaters, which work like an inverse fridge. Rather than taking heat from the food inside and dumping it outside the fridge, these take heat from the outside air and put it into the water. 

You likely have a water heater with an “energy factor” (or EF factor) of one or less and should consider upgrading.  You are better to get one with a much higher energy factor. I recommend one of the many models on the market with an energy factor over 3. By doing so, you can cut your water heating bill in the summer by 2/3 or more.


Drain water heat recovery systems

drain water heat recoveryIn the discussion of hot water, we haven’t yet talked about what we can do with all the hot water that goes down the drain.

There are several manufacturers of drain water heat recovery systems in Canada, including one right here in Waterloo Region. These systems are passive heat exchangers which recover energy from shower water as it goes down the drain and preheat the cold water entering the water heater. These relatively inexpensive systems make the most sense where there are a lot of showers taking place, such as in a house with several occupants.

What about solar hot water heaters?

While on the topic of hot water, you might have noticed that we haven’t discussed solar hot water yet.

I can’t recommend them for a single family home–at least not with the current alternatives available–due to a combination of factors such as lower water use, and complex systems for a freezing climate resulting in higher costs. Why? See this article on GreenBuildingAdvisor.com.

To improve your use of energy, you are better off installing solar panels on the roof and an air source heat pump water heater in the basement, than putting in a solar hot water system on a single family home.

Multifamily, commercial or industrial use may still have great applications and cost paybacks, or installing a simple heater for an outdoor pool. Used in those settings, they make sense.

Never run out of hot water again!

One piece of technology that you may find useful is what is called a tankless water heater (also called an instantaneous water heater). They heat water up on demand and don’t store hot water (though some models store tiny amounts to avoid a cold water plug).

Because of colder ground temperatures in Canada, a unit that can provide up to 200kBtu/hr output is recommended when providing water to the whole house.

Due to the high-heat input, you won’t run out of hot water ever again. That could create a challenge if you have teenagers and need to use the washroom sometime this century!

As a result of this feature, the cost savings from having no standby losses (when heat is lost from the water tank) have historically not been found in water heater replacement studies.

Water conservation is important

So helping make your home more energy efficient is a good reason to conserve water. If you are trying to living sustainably, there are several more good reasons. REEP Green Solutions has an upcoming series of posts on this important topic.

Feature photo credit: Kevin Flood

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