Person washing hands in hot water

Are Instant Hot Water Systems Worth It?

In a world where everything is automated or instant, it comes at no surprise there are instant hot water systems. Also referred to as a continuous flow water heater, these systems give you virtually endless hot water, and you only pay for the water you use. Additionally, there’s no need for those ugly, bulky storage tanks! Instant hot water is a discreet wall-mounted tankless system. According to the Australian Energy Foundation electric hot water system costs more than twice as much to run than a gas instant hot water system?

These all sound too good to be true. You’re probably even thinking that there’s a catch somewhere. Metropolitan Plumbing has over 25 years of experience in hot water, and we’re here to let you know if instant hot water is really worth it. As your hot water experts, we’re going to run you through the pros and cons of instant hot water systems.

How Do Instant Hot Water Systems Work?

The primary benefit of instant hot water is that they only heat water as you need it. This is as opposed to a storage tank water heater where water is heated and stored until you want to use it. You heat the entire tank, regardless of whether you use it or not.

You will find most instant water heaters use natural gas as their energy source, however electric variants are also available. When you turn the hot water tap on, this triggers a flow sensor. This switches on a gas burner or electric element. This heats water in a serpentine-shaped copper tube around a heat exchanger.

The hot water is pumped out and delivered to the fixture. Coldwater takes its place for heating. While the hot water tap is on, water is continuously heated. When it is turned off, the heating element/burner also turns off.

Generally speaking, it is more cost effective and energy efficient to opt for a natural gas power source. However, whenever natural gas is not available, electric instant hot water is the alternative.

What Size Do I Need?

Unlike traditional water heaters, instant hot water systems are tankless! This means there isn’t a size in particular that will suit your home’s needs. Rather, you need to look for a flow rate that will meet your water demands. Flow rate is the amount of water in litres that the system can heat and deliver per minute.

You will find flow rates between 10 to 32 litres per minute typically. When selecting a flow rate, you can’t just look at the number of bathrooms and people in your home. There are a few other things you need to consider:

  • How many people take showers at the same time?
  • Do you use hot water for your dishwasher or washing machine?
  • Are people in the shower at the same time the dishwasher or washing machine is being used?
  • Do showers have water-saving shower heads installed?

It’s important you choose the right flow rate to avoid paying more upfront than you need to. It might also result in a greater operating cost.

Another benefit of instant hot water systems is that they are small in size, being a tankless, wall-mounted unit. This also makes these systems a great option for homes with limited space outdoors, or for units and apartments.

Is it Safe?

Yes! Instant hot water systems are arguably safer than storage tank water heaters, in fact.

There’s always the risk of stored water growing bacteria. This is why the thermostat for hot water systems is always set to 60°C or above. Bacteria such as Legionella can grow in water sources and cause you to develop Legionnaires’ disease and Pontiac fever.

90% of Legionella die in 2 minutes in 60°C water. In water above 70°C, all Legionella die almost instantly. Thermostats can become faulty or accidentally knocked without realising it. If this occurs, your storage tank is at risk of growing this bacteria.

Storage tanks will also corrode over time. When this happens, you might start to see rust in your water. Instant hot water systems don’t store water in the first place, and so never run the risk of growing harmful bacteria or rusty water!

Because you don’t need to heat the water as much, the risk of burns from too hot water is greatly reduced as well. In fact, it is required by Australian standards that storage tanks have a tempering valve installed which only allows 50°C to be delivered to fixtures used for personal hygiene. These valves mix your cold water supply with the 60°C from the storage tank in an effort to minimise scalds. This valve is made redundant by instant hot water systems, as the thermostat of these systems can directly by set to 50°C!

How Long Do Instant Hot Water Systems Last?

The typical storage tank hot water system will last you anywhere between 8 and 12 years with proper maintenance. We have found that instant hot water systems tend to last longer than their storage tank counterparts. It’s not uncommon to see them last up to 20 years!

In order to get the most out of your water heater and ensure it is running efficiently, it needs regular servicing. This will not only extend the life of your instant hot water system but will mean you won’t be wasting water and energy where you don’t need to.

Does Instant Hot Water Save Money?

When installed appropriately, an instant hot water system will save you money in the long-term. While they are more costly upfront, you will save money by only paying for the hot water you use. You won’t need to worry about heat loss from a storage tank either.

On average, we have found that instant hot water systems last longer than storage tanks as well. Coupled with the absence of sacrificial anodes that need to be replaced every so often as is the case with storage tanks, instant hot water will be sure to make your wallet happy.

Not only are you using less energy on your hot water, but you’ll be contributing less carbon dioxide gas emissions as well. So your instant hot water system will benefit both your wallet and the environment!

What are the Downsides of Instant Hot Water?

If instant hot water systems are so good, why doesn’t every single home have one? While instant hot water comes with these benefits, there are some negatives as well.

Despite the name, “instant” hot water, you don’t actually get hot water instantly. There is a delay between turning the tap on and the water reaching the set temperature. It doesn’t take long, but you can experience some additional water waste while waiting for the heat.

In order to heat the water, a certain amount of water must be flowing with the hot water tap on. A combination of low flow showerheads and a trigger flow rate that is set too high might mean your shower won’t trigger water heating! This can be easily avoided by ensuring you use a licensed plumber and informing them of fixtures that might affect this.

The final concern with instant hot water is that the flow rate may not meet the demands of a large family. When the hot water demand exceeds the output of the instant water heater, you might experience low water pressure. This is simply because the hot water is being thinly spread in an effort to give everyone hot water. Scheduling hot water use so that demand doesn’t exceed the flow rate output will avoid this. For homes with stubborn family members who won’t budge on their shower time, a storage tank hot water system might be better suited. 

Still not sure if an instant hot water system is right for your home? We have Hot Water Systems: The Complete Guide to help you pick the best option for your home. We know everything there is to know about hot water and can help you pick between instant hot water systems, heat pumps, electric hot water heaters and more.

To learn more about instant hot water systems, contact Metropolitan Plumbing.


Published: 24 Jul, 2020

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