How to size a water heater for your home
The right water heater matches your household’s peak demand. Too small and you run out of hot water; too big and you pay to heat water you never use. Here’s how to get it right.
Size by household
As a rule of thumb: 1–2 people suit about a 40-gallon tank, 3–4 people about 50 gallons, and 5 or more people 60–80 gallons. Add capacity if you have extra bathrooms or a soaker tub that draws a lot at once. What really matters is the "first-hour rating" (how much hot water you can draw in a busy hour), not just the tank size.
Tank vs. tankless
A tank stores hot water and reheats it. Tankless heats water on demand, so you get endless hot water and a smaller footprint, but it’s sized by flow (gallons per minute) rather than gallons. In an Ontario winter the incoming water is colder, so tankless units need more BTU to keep up. Size for cold-weather flow, not the headline number.
Fuel and efficiency
Common options are natural gas (power vent), electric, and a hybrid heat-pump water heater. Hybrids are the most efficient to run but cost more upfront. If you’re renting, the monthly price already bundles service, so efficiency mostly affects your energy bill.
Not sure? Let us size it
Answer a couple of questions in our sizing tool and we’ll match you to the right model from our good, better, and best options. An advisor confirms the exact fit for your home before you book.