What Tank Size Do I Need For My Hot Water System?

When it comes to hot water, the choices you have for replacing your current unit are now vast and varied.

With instantaneous, storage, gas, solar, electric and heat pump options on the table, you’d be forgiven for getting a little confused with where to start.

If you’re considering a storage system in order to allow for an ample, on-demand hot water supply in your home or office, we’ll put it this way: choosing the correct tank size for your system is essential for ensuring a consistent supply of hot water whilst also optimising its energy efficiency: a huge factor in determining long-term operating costs.

Understandably, with a wide variety of hot water systems available, each with unique considerations, it’s important to understand the different types and factors that influence tank size.

In this article, we will explore the various hot water system options, focus on storage-based systems, discuss the factors affecting tank size requirements, and highlight the advantages of heat pump hot water systems in terms of reduced bills and extended lifespan.

So – let’s dive in!

What are the different types of hot water systems?

There are several types of hot water systems commonly used in households. These include storage-based systems, instantaneous (or continuous flow) systems, heat pump systems, and more.

Let’s take a close look at each of the main types:

Storage-based hot water systems

Storage-based systems, also known as hot water heaters or hot water cylinders, store heated water in a tank for later use. This type of system is the most common in residential settings.

Storage-based systems can use various fuel sources, including electricity, gas, or solar power, to heat the water in the tank. They provide a ready supply of hot water, but the capacity of the tank determines the amount available at any given time.

Instantaneous systems:

Instantaneous or “continuous flow” hot water systems heat water on demand, providing hot water as needed without the need for a storage tank. When a hot water tap is turned on, cold water passes through a heat exchanger, which quickly heats the water to the desired temperature.

In general, instantaneous systems are known to be compact, energy-efficient, and suitable for smaller households or locations with limited space.

Heat pump hot water systems:

Heat pump hot water systems extract heat from the surrounding air and use it to heat the water in the tank. These systems work on the principle of heat transfer and are highly energy-efficient.

Heat pump hot water systems are particularly advantageous in moderate climates where ambient air temperatures remain relatively stable. Notably, they can reduce energy consumption and provide significant cost savings over time.

Heat pump systems can achieve efficiency ratings above 300%, meaning that for every unit of electricity consumed, they can produce three units of heat energy or more. This makes heat pump systems significantly more efficient than their gal/electric hot water system counterparts.

Solar hot water:

Of course, solar hot water systems use the sun’s energy to heat water. They consist of solar collectors (panels) that capture sunlight and transfer the heat to a storage tank. Solar systems can be either passive or active, with active systems using pumps to circulate the heated water.

Solar hot water systems are environmentally friendly, highly energy efficient and can provide substantial energy savings, especially in sunny regions.

In this article, we’ll focus on storage systems. Choose a storage hot water system and you have multiple options for powering it – including solar, heat pump, and more.

We’ll delve into your options a little later in the article.

Understanding the factors influencing tank size

Determining the appropriate tank size for a storage-based hot water system depends on several key factors, as outlined by the Victorian Government Department of Energy, Environment and Climate Action (2023).

Let’s take a look at them now:

Household size: The number of people in your household directly impacts the demand for hot water. Larger households typically require a larger tank size to ensure an adequate supply for simultaneous hot water usage.

Peak demand: Consider peak hot water usage periods, such as mornings when multiple family members may be showering or when you need to use hot water for laundry and dishes. The tank size should be able to meet the peak demand without running out of hot water.

Water consumption patterns: Understanding your household’s hot water usage patterns is essential. If you have a consistent demand for hot water throughout the day, a larger tank may be necessary. On the other hand, if your usage is sporadic or limited, a smaller tank can do the trick.

Demand: Do you have several members of the household who shower one after another, at approximately the same time (e.g. in the morning, before work?). Factors like this not only influence decisions regarding which system is right for you (e.g. storage/instantaneous), but also the ideal size of your tank (if you choose a storage system).

Efficiency and recovery rate: Different hot water systems have varying recovery rates, indicating how quickly they can reheat water once it’s been depleted. Consider the efficiency and recovery rate of the system when determining the tank size required to meet your household’s hot water needs.

What different tank sizes are available for hot water systems?

In Australia, storage hot water systems typically range from smaller capacities of around 50-80 litres (for compact units) to larger sizes of 250-400 litres or more. Here are some other common sizes available on the market:

50 litres: Generally suitable for single-person households or small apartments with limited hot water usage
80 litres: Generally ideal for couples or small households with minimal hot water demand
125 litres: Often suitable for small to medium-sized households with moderate hot water requirements
160 litres: Adequate for small to medium-sized households with a slightly higher demand for hot water
250 litres: Commonly used for medium-sized households with multiple occupants and average hot water usage
315 litres: Often suitable for larger households with higher hot water demand, particularly if there are more than four occupants

It’s important to note that these sizes align with very general guidelines regarding the availability of various sized tanks, and the optimal tank size for your specific needs may vary. Our award-winning G Store team can help you pick the exact tank suitable to your specific needs and budget – just give us a call today on 1300 137 567!

What are the issues that can result from choosing the wrong tank size?

With the help of an experienced hot water retailer such as G Store, you’re unlikely to encounter this issue in the first place.

However, should you find yourself in the unfortunate situation that your tank size is not suitable for your particular needs, The Victorian Government Department of Energy, Environment and Climate Action (2023) notes that you might experience issues such as:

Regularly running out of water (if the tank is too small)
An increase in running costs and monthly bills (if the tank is too large)

But just a minute… let’s touch base about heat pump hot water

Storage or instantaneous? It’s not the only choice you’ll have to make when it comes to replacing your current hot water system.

If you’re looking for a high-quality replacement that will stand the test of time, it’s also worth noting that heat pump hot water systems are ever-increasing in popularity due to their energy efficiency and eco-friendliness.

These systems extract heat from the surrounding air to heat the water in the tank, resulting in lower energy costs and significant energy savings overtime. Here are some major advantages of heat pump hot water systems:

Reduced bills: Heat pump hot water systems are highly efficient, consuming less energy compared to traditional storage-based systems. According to the Australian government’s YourHome resource, heat pump hot water systems can save up to 65% on hot water costs, leading to substantial bill reductions.

Longer lifespan: Heat pump systems have a longer lifespan compared to conventional hot water systems. The Australian government estimates the average lifespan of heat pump hot water systems to be around 15 years, providing long-term durability and value.

Flexibility: Did you know that a heat pump can facilitate a variety of systems in your home? From hot water to hydronic heating to heating your swimming pool and a whole lot more, it’s worth looking into heat pumps – if only for their flexibility!

Wrapping up

Selecting the right tank size for your hot water system is crucial for ensuring a reliable supply of hot water while maximising energy efficiency. Consider factors such as household size, peak demand, water consumption patterns, and the efficiency of the system itself.

If you’re looking to replace your existing hot water system, however, it’s also worth noting what other variety of choices there are on the table. From this angle, exploring the advantages of heat pump hot water systems, such as reduced bills and extended lifespan, can also make for a smart choice in the short-term, and huge cost savings in the long run.

Don’t know where to start? With 15+ years of hot water expertise, that’s where the award-winning team at G Store comes in! Give us a call today on 1300 137 567 to discuss your options, or visit our Learning Centre now to read more.