According to Natural Resources Canada, water heating represents 15 to 25 percent of our household energy bill and it is the second largest portion of energy utility costs, after home heating. So before calculating the right water heater size you need for your household, you should consider switching to an eco-friendly water heater.
Next you have to make sure to get the right capacity tank for your family’s needs. Getting one with too much capacity will cost more to rent and operate. As a general rule, below is a guideline of the size of tank you might need. While it does not necessarily factor the number of bathrooms in the house and your hot water usage, it should give you a good estimate:
|Number of gallons/litres||Number of people in the household|
|30-40 gallons (114 -151 litres)||1-2|
|40-50 gallons (151-189 litres)||2-3|
|50-60 gallons (189-227 litres)||3-4|
|60-80 gallons (227-303 litres)||5 people +|
Source: What Size Water Heater Do I Need
If you want to make a more precise calculation, you have to check two factors:
The First Hour Rating (FHR): it means how many gallons of water a heater can produce at any given hour. You can see this number on the EnergyGuide label of the water heater.
Peak Hour Demand: this corresponds to the amount of hot water your household uses during a busy hour, like in the morning for example. The easy method to calculate is the number of people living in your household multiplied by 12 (it corresponds to the FHR). For example, if you are 4 people in your household 4 x 12 = 48 which corresponds to your FHR. So you will want to buy a water heater of about 50 to 60 gallons (189-227 litres).
Once you know what size water heater you need, you can start shopping. You might consider renting. In your calculations, remember that the life expectancy of a water heater is about 7 to 15 years before being replaced. When you rent, make sure to also take in consideration the following: Natural Resources Canada explains that “Every energy-using appliance has two price tags. We know the first: the purchase or renting price. The second price tag is considered less in the purchasing or rental decision, but is just as real; it is the operating cost of the appliance which is the cost to operate the heater. It is wise to rent a model that is EnergyStar, as you will save in the long run.”