Sept. 13, 2017 | David Dodge and Scott Rollans

Getting yourself in hot water

Choosing the best high-efficiency water heater

A typical hot water heater accounts for about one-fifth of the energy used in most Canadian homes.

Choosing the right hot water heater, therefore, can have a huge impact both financially and environmentally – especially as energy prices and carbon levies continue to rise.

Many of us still choose conventional, gas-fired hot water tanks because they're cheapest – but are they really? The initial price of your hot water heater can represent as little as 12 per cent of the overall cost over its lifespan. The other 88 per cent is energy.

For that 88 per cent, we wanted to get the biggest bang for our buck. So, we asked Ken McCullough of Think Mechanical to walk us through three high-efficiency choices: conventional-style, high-efficiency, power-vented tank; on-demand tankless; and hybrid heat pump.

"The more people you have in your home, the more hot water you're going to use," said McCullough. "It's important to know that you have the highest efficiency that you can possibly have. Otherwise, you're just throwing money out of the window."

These days, hot water heaters all come with an energy factor (EF) rating. A tank with an EF of 1.00 would be perfectly efficient, with all the energy being converted to hot water. This factor is often expressed as a percentage. A standard tank has an efficiency rating of about 60-65 per cent, meaning 35-40 per cent of the energy goes up the flue, or radiates out as the water sits in the tank.

You'll also want to look at your new system's recovery rate – the rate at which it can heat the fresh water flowing into the tank. The higher the rate, the less likely you are to run out of hot water during heavy use. Here we present three great choices for dramatically increasing the efficiency of your water heater:

High-efficiency, power-vented water heater
If you're reluctant to adopt new technology, you might consider a high-efficiency, power-vented tank. It looks like an old-school water heater, complete with a 50-gallon tank, but it's side-vented (like a high-efficiency furnace) to decrease heat loss. This helps boost its efficiency to 90 per cent, making it about 30 per cent more efficient than a traditional tank. Meanwhile, its very high recovery rate – 80 per cent in one hour – will help keep the hot water flowing. You can get a 79-per-cent-efficient model for $2,700, but the highest efficiency model we looked at clocked in at more than $4,800 installed.

"It's important to know that you have the highest efficiency that you can possibly have. Otherwise, you're just throwing money out of the window." - Ken McCullough, Think Mechanical

Tankless, on-demand water heater
We were particularly interested in an on-demand, tankless water heater. As the name suggests, this heater kicks in only when you turn on the hot water tap, heating the water as you use it rather than storing it in a tank. It heats the water quickly enough to provide an endless supply, assuming you're not using a lot of hot water all at once (say, washing clothes and running the dishwasher while you shower). "You're going to turn on your tap, and you'll get hot water," said McCullough.

With efficiency ratings of 95-97 per cent, these are the most energy-efficient options available when it comes to natural-gas water heaters. At 95 per cent efficient and priced at $3,700 installed, going tankless is more expensive than opting for a conventional water heater, but the long-term savings more than balance that out. And, because there's no tank, the system frees up a lot of space in your furnace room.

Heat pump water heater
McCullough also showed us the state-of-the-art option for efficient water heating: a hybrid heat pump water tank. It looks like a conventional tank, but with a cap on top containing a heat pump. The heat pump draws heat from the air in the mechanical room – like a refrigerator in reverse – and transfers that heat to the water. This allows the heater to achieve an efficiency rating of 330 per cent, meaning the heat energy transferred to the water is more than triple the amount of electricity consumed.

Because the heat pump water heater is entirely electric, it is perfect for net-zero homes with no gas hook up (meaning you also save $60 per month on gas-line administration and delivery charges). Some early adopters are choosing these in conventional homes as well. McCullough quotes $4,400 for this option, making it slightly cheaper than the high-efficiency power-vented tank. The one downside is its relatively slow recovery rate of just 80 litres per hour.

Our choice: tankless, on demand water heater
In the end, we went with a Rinnai tankless water heater in our own home. We consider ourselves early adopters, and we loved the idea of having an endless supply of hot water. A home improvement rebate from Energy Efficiency Alberta helped put us over the top.

So far, we're thrilled with our choice, although the quirks of the system created a few start-up challenges. For example, our daughter's first shower started out hot, but quickly switched to freezing cold. The culprit seemed to be our low-flow shower head. It turns out that on-demand heaters require a certain minimum flow rate to remain on. We solved the situation with a single quick adjustment – turning down the temperature setting from 60 C to 49 C on the water heater, thereby increasing the proportion of hot water needed for a comfortable shower. This has an added benefit of saving more energy.

It does take a few seconds longer for the hot water to arrive, but once it does, it will keep coming for as long as you need it.

That said, please don't tell our daughter she can now shower for hours.

The Smart Home series was created by GreenEnergyFutures.ca for the Alberta Emerald Foundation with financial support from the Alberta Real Estate Foundation. 

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