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Instant Hot Water System vs Storage Hot Water System - Instantaneous Hot Water System vs Hot Water Storage

When it's time to get a new hot water system, three of the most asked questions are:

1.  “Should I get a traditional storage hot water system or an instant hot water system?”

2.  "What size hot water system do I need?"

3. "What is the best instant hot water system or storage hot water system?"

When you compare instant hot water systems, the best instant hot water system is the instant gas hot water system from Rinnai. It provides instantaneous hot water that is reliable, efficient and best value for money. But is it better than a storage hot water system?

Both types of hot water systems supply hot water but they do it in different ways. 

Instant hot water systems sizing is best determined by peak demand whilst storage hot water system sizing is generally based on the number of people.

We review the two hot water system types and compare the pros and cons of both, as well as the prices, to help you make an informed decision...

Running Out of Hot Water - Instant Hot Water System vs Storage Hot Water System

running out of hot water - Continuous Hot Water System vs Hot Water Storage TankWith the best instant hot water system, the water is heated as you use it. The instant hot water system can better maintain the flow rate indefinitely.

So, you basically never run out of instantaneous hot water, no matter how many people get to the shower before you.

Traditional storage hot water system can only heat a certain number of litres at a time. 

Residential gas storage hot water system are typically in the 135L to 170L range. 

Off-peak electric storage hot water system need to have a much larger capacity, as they have to last through the entire day.

Once all of the hot water storage in the tank is used up, it takes time to heat up the fresh water entering the tank. 

If it runs out right in the middle of a shower, you have an uncomfortable problem. 

You can finish with a cold shower or just stay soapy while you wait for the water to reheat.  Neither is a good choice.

Continuous Hot Water System - Instant Hot Water System

With a continuous hot water system (instant hot water system) the water is heated as you use it instead of storing it in a tank. The compact wall mounted unit can maintain the flow rate indefinitely, as long as a tap or shower is turned on, hence the name. The systems are typically continuous flow gas hot water (instant gas hot water system) but electric continuous hot water systems are also available.

Electric Continuous Hot Water Systems vs Gas Continuous Hot Water Systems

The best instant hot water system is still a gas instant hot water system. Electric continuous hot water are relatively new and untested. Gas instant hot water systems have been refined over many years. Gas instant hot water systems now have 6 or 7 Star ratings, which you won't fine with an electric unit. Electric continuous hot water are also more expensive.

Energy Consumption

The best instant hot water systems now have 6 or 7 stars, the highest possible energy ratings. Continuous flow through hot water heater systems are better as they only need to run when the hot water is actually required and wasteful pilot lights are a thing of the past. 

On the other hand, with a storage hot water system the best energy ratings is 5 stars, as you have to use energy to maintain the temperature of the stored water 24/7. 

The technology and energy saving designs are also very different. 

Best Gas Instantaneous Hot Water System

Gas Hot Water Systems Review - Tankless Continuous Flow

The best gas instantaneous hot water system would also be the best continuous hot water system. A gas instantaneous hot water system is also arguably the best gas hot water heater and the best hot water system.

Gas instantaneous hot water system is up to 7 star money saving energy efficiency, compact, aesthetically pleasing, no issues with Legionnaires' disease, and best of all they have a coninuous flow of hot water that never runs out.

This all makes the best gas instant hot water system (best continuous hot water system) the best hot water system.

Gas instantaneous hot water systems are better as they provide hot water on demand whenever you turn on the tap, as you need it.

These units only heat the water as it passes through so there is no storage tank.  

This also means you never run out of hot water. 

Energy Star Ratings - Best Instant Continuous Flow Hot Water & Hot Water Storage Tank

Star rating labelModern tankless continuous flow through hot water heater systems typically have a better 6 Star energy rating. The best instant hot water systems are now available in 7 Star units. The best selling instant hot water system is the Rinnai Infinity 26.

Better tankless continuous flow hot water heater systems are available in both natural gas and LPG models.

In contrast, the best storage hot water system are only rated at 4 or 5 Stars. The best selling 5 star storage hot water system is the Rheem Stellar.  

This means both the energy consumption and the running costs will be higher. 

Storage hot water system are available in electric, natural gas and LPG models.

So, while we'd love to sell you more gas, we'd rather have you saving money and energy with the more efficient models. 

Continuous flow hot water system are also the best choice for the environment.

Storage Hot Water System vs Instant Hot Water System - Size and Aesthetics

Tankless hot waterAt about the size of a small suitcase, instant hot water systems are better as they are much smaller than a traditional storage hot water system. Mounted flush against the wall, the smaller instant hot water systems take up less space and instant hot water systems have the best aesthetics, as they don’t dominate the exterior appearance of your home.

A storage hot water system is big, especially the electric off-peak models. 

Even when installed outdoors, the size can get in the way, particularly with today’s smaller lot sizes. 

Having this large object next to your house also does nothing for the appearance of your home.

Storage Hot Water System vs Instant Hot Water System - CO2 Emissions

Greenhouse gas emissions are better reduced through the use of instant hot water systems. Instant hot water systems produce about 75% less CO2 greenhouse gas emissions and are better when compared to a storage hot water system powered by coal-fired electricity.

Even when compared to gas hot water storage tank units, instant hot water systems are better and more eco-friendly. 

The best instant hot water systems have 6 to 7 Star ratings consume less gas and create less CO2.

Storage Hot Water System vs Instant Hot Water System - Life Span

The best instant hot water systems can last up to 20 years. Warranties for instant hot water systems are typically better, at 10 to 12 years.

Traditional storage hot water system have a life span of around 10 to 12 years. 

Warranties for a storage hot water system is typically only 5 to 10 years.

Storage Hot Water System vs Instant Hot Water System - Water Quality

The best instant hot water systems has the best water quality, since there's no tank to rust and no water stored with an instant hot water systems, the water is better, staying cleaner and fresher.

Water from a storage hot water system may pick up bits of rust and scale that build up within the tank. 

Storage Hot Water System vs Instant Hot Water System - Speed

When you first turn on the tap, there is typically a delay in getting hot water, as the water in the pipes leading from the water heater to the tap will be cold. Because it is kept hot, a storage hot water system can be slightly faster in delivering the initial flow of hot water, as the best instant hot water systems takes a second or two for the unit to get up to temperature.

However, now there is a new system to eliminate the delay entirely. 

The Rinnai Smartstart® Water Saver was developed to be the best instant hot water systems and reduce water wastage whenever a hot water is turned on. 

It pre-heats the water in the pipes before you turn on the hot tap. 

It is part of why the Rinnai Infinity range are the best instant hot water systems.

Cheap Gas Water Heaters?

In the past, there was a substantial difference in the price between cost of instant hot water systems and storage hot water system. The difference has now shrunken to the point where there is almost price parity between comparably sized units. This is especially true if you are comparing 5 Star storage hot water system to the best instant hot water systems with 6 or 7 Star ratings.

Everyone wants cheap gas water heaters.

However, the days of super cheap 3 Star storage hot water system are long gone, as are their higher operating costs. 

Cost of Instant Gas Hot Water System Price - Instantaneous Hot Water Price

Cost of an instant (instantaneous) gas hot water system price (instantaneous gas hot water systems prices) is typically from around $700 to $1500*. The instant gas hot water system price difference depends on the flow rate which is, in turn, dependent on the number of showerheads and taps.

Storage hot water system range in size from around 130L to 350L, with gas hot water system prices from approximately $800 to $1450*.

Efficiency star ratings also influence the instant gas hot water system price (instantaneous gas hot water systems prices), with higher star ratings typically cost more in both types.

*Note that instant gas hot water system price (instantaneous gas hot water systems prices) are indicative only, as of July 2019

Storage Hot Water System vs Instant Hot Water System - Health & Safety

Storage tank hot water heater The best instant hot water system maintains a bacteria free system with safer temperature that minimises scalding.  An instant hot water systems is better at the prevention of bacterial growth, as there is no stored water in which bacteria can breed. Instant hot water systems can be better set at 50ºC, so the risk of scalding is greatly reduced without the need of a tempering valve.

With storage hot water system, there is the potential for bacteria growth within the tank. 

The World Health Organisation -- WHO -- recommends that a storage hot water system be kept at a minimum of 60°C. 

Unless a minimum of 60°C is maintained, storage hot water system tanks can be a breeding ground for Legionnaires’ disease, or Legionellosis, that is caused by a bacterium, Legionella pneumophila. 

It is a respiratory disease that can cause severe pneumonia and is sometimes fatal.

However, Canadian studies have shown, even when the thermostat is set at 60°C, a high percentage -- approximately 40% -- of electric storage hot water systems remain contaminated. 

This is because of the lower temperature, of about 30°C to 40°C, at the bottom of the hot water storage tank.

How a Tankless Continuous Flow Through Hot Water Heater Works

Schematic of continuous flow hot water heaterIn summary:

• Cold water flows through the continuous flow hot water heater when a hot water tap is opened inside your home.

• The water flow is detected by a sensor that ignites the gas burner, to heat the water in the heat exchanger.

• The water typically follows a serpentine pattern through the heat exchanger, absorbing as much heat as possible as it flows through the hot water heater.

• An electronic control unit modulates the gas burner to maintain a set water temperature.

• Available in LPG and natural gas continuous flow hot water models

See all the details on:

How a Tankless Hot Water Heater Works

Hot Water System Sizing?

Don't Calculate by Number of People or Bathrooms

The sizing information available is very confusing because manufacturers, and others, are trying to provide a simplified answer to a complicated question. 

Some suggest that you calculate by the number of bathrooms in your home while others say to go by the number of people in your family. 

Also, in many cases, their recommendations are based on the worst case scenarios, assuming higher consumption than your actual water use.

Buying Too Large Wastes Money

The result is that many people end up buying a larger system than they actually need. 

This costs them extra money when they buy the hot water system and will increase the ongoing operating costs, in many instances.

Factors to Really Consider

Simultaneous use is one of the fundamental determining factors.  

The number of people in your home combined with how and when they use hot water is the key. 

  • Do they all take showers at the same general time of day? 

  • Do they take showers simultaneously in different bathrooms?

  • Do the showers have WELS 3 Star Rated water saving shower head (maximum 9L/Min) or standard 18 to 25L/Min showerheads?

  • Do some prefer baths, which use more hot water? Is the bath or spa oversized, requiring even more hot water?

  • Do you run the washing machine, using hot or warm water, while people are showering?

  •  Is your dishwasher connected to the cold or hot water? If hot, do you use it while hot water is being used elsewhere?

Showers Are the Key - Water Saving Shower Head

Showers use the most hot water in a home.  People generally shower for 5 to 10 minutes. Assuming you have a 3 Star water saving shower head and you mix in some cold water with the hot, the typical hot water consumption would probably be in the 7 litres per minute range. 

If you also assume an 8 minute shower, water saving shower head will consume about 56 litres of hot water per shower or a family of four would consume 224 litres. 

The use of WELS (Water Efficiency Labelling and Standards) 3 star rated water saving shower head is an important factor in saving water and energy whilst reducing the size and cost of the hot water system required.

Hot Water Tank ExampleRinnai HOTFLO 170 gas hot water system

In the above example, if all four people take their showers in the morning, you would only need a hot water storage system with 224 litre first hour capacity, regardless of how many take showers at exactly the same time.  

This all presumes that you are not using any other hot water devices at the time.  

The use of additional hot water, after the shower period, would depend on the hot water system’s recovery time required to achieve full temperature.  

So, with a larger family or house guests, a bit of scheduling may be required to avoid the need for a larger storage hot water system.

Off Peak Electric Issues

Off peak electric hot water storage units are a completely different story. Inasmuch as they only heat water at night, hot water storage needs to be quite large to make sure you don’t run out of water during the day. 

So, some of the electric savings is offset by the fact that you need to heat a larger storage hot water system. 

The bigger hot water storage tank would also cost more to purchase.

Tankless Continuous Hot Water System Example

Bosch 21e tankless gas hot water systemFor a tankless continuous hot water system unit, it would depend on how many showers are being used simultaneously. 

Using the example above, if it’s two showers, then you only need a unit with a minimum flow rate of 14L/min. 

If you have 3 people showering at exactly the same time, you would need a minimum 21L/min.  

This does assume that you are not using other hot water devices simultaneously. 

A continuous hot water system is better, as the recovery time is not an issue with continuous flow units, so even a large family with guests would not run out of hot water.

Compare Gas Hot Water Heater Systems Prices

Now you can compare prices for all the major brands of gas hot water systems including Rinnai, Bosch, Kelvinator, Rheem, Dux and AquaMAX.

Click on your category of interest to compare prices:

Tankless Continuous Flow Gas Hot Water Systems Prices

Gas Hot Water Storage Tank Systems Prices

Gas Boosted Solar Hot Water Systems Prices

 

Gas Hot Water Special Offers

Please click on promotion for full details*

Bosch 17e, 21e & 26e Gas Hot Water Systems

Rinnai Infinity 16 & 20 Gas Hot Water Systems Sale

Rinnai Infinity 26 Touch

Special E2G™ LPG gas hot water pricing
 
 
 
 

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The information in this article is derived from various sources and is believed to be correct at the time of publication. However, the information may not be error free and may not be applicable in all circumstances.