Tank or tankless: what to weigh before you replace your water heater

When a water heater fails, most people replace it with the same kind. That is often the right answer, but it is worth five minutes to think about whether tankless suits your house better.

How each one works

A tank heater keeps 40 to 50 gallons or more hot all the time, ready to use. When it runs out, you wait while it heats the next tank.

A tankless heater heats water as it flows through. Turn on a hot tap and it fires up; turn it off and it stops. It never runs out, but it can only heat so many gallons a minute.

The questions that decide it

How much hot water do you use at once?

A tankless heater is sized by flow. Two showers and the dishwasher at the same time need a bigger unit than one shower. A tank heater is sized by how much it stores. Tell us how your household uses hot water and we can size either one properly.

What does the install involve?

Swapping a tank for a tank is usually straightforward. Going tankless can mean a larger gas line, new venting, or for an electric unit, a bigger electrical supply. That is where most of the difference in price comes from.

How long will you stay in the house?

Tankless heaters cost more up front and less to run, because they don't keep a tank hot around the clock. They also tend to last longer. The longer you stay, the more that evens out.

How much room do you have?

A tankless unit hangs on a wall and frees up the closet or corner the tank sat in. In a small house or a condo that space can matter.

When we'd suggest staying with a tank

• Your gas line or electrical panel would need a big upgrade for tankless
• You plan to sell in the next few years
• You want the lowest cost to replace today

When tankless makes sense

• Your household regularly runs out of hot water
• You need the space back
• You plan to stay put for many years

What happens next

Our replacement estimate visit is free and takes about half an hour. We look at your current heater, the space, the venting and the gas or electric supply, and give you a price for the option that fits. You decide in your own time.