9 Answers To What Size Hot Water System Do I Need?
Trying to figure out the answer to the common question of what size hot water system do I need can feel like a guessing game. When you’re juggling household needs and your budget, it’s one of the most common questions we ever hear. Whether you’re replacing an old system or planning for a new build, choosing the right capacity is critical – too small, and you’ll run out of hot water during peak times. Too big, and you’ll waste money heating water you’ll never use.
It’s hard, and we know it.
The perfect hot water system for your place depends on:
- How many people live in your home
- How you use water
- The time of day you typically use it
- And what type of system you’re running – electric, gas, solar, or heat pump.
Let Fix-It Right Plumbing break it down and make this decision easier:
1. Why hot water system size matters
A poorly sized system isn’t just annoying – it can really cost you money. If your system is undersized, you might be halfway through a shower when it runs cold. Oversized systems? That means higher energy bills for no reason, as you’re paying to keep water hot around the clock that just sits there and goes cold.
The good news? Once you understand the basics, choosing the right size becomes a whole lot easier:
2. Start with household size & usage habits
The most obvious starting point is how many people live in your home – but just as important is how much hot water you all use:
- Do you take long showers?
- Do you run the dishwasher daily?
- Do you have teenagers who treat the bathroom like their second bedroom?
If you’re asking what size hot water system is perfect for your place, the answer depends on more than just headcount – it’s about how your household BEHAVES.
Here’s a rough guide based on average daily usage in litres:
1-2 people: 100-160L
3-4 people: 160-250L
5+ people: 250-400L+
3. Different types of systems = Different sizing rules
Electric storage, gas storage, continuous flow, solar, and heat pump systems. That’s a lot of technologies, but remember this – they all have quite different output capacities. For example:
- Electric storage units heat water and store it in a tank, so you need to choose a size based on how much you’ll need at peak time.
- Gas systems recover faster, so the tank doesn’t have to be as large.
- Continuous flow systems (also called instantaneous systems) don’t store water at all – they heat on demand.
- Heat pump systems are more efficient, costing you less.
- Solar systems can cost you nothing at all – but you’ll need to pay to get it all up and running!
You get the picture – and it’s why there’s no one-size-fits-all answer when it comes to a question like what size heat pump hot water system do I need. To sum it all up – the technology changes how size is calculated, so there’s almost never an exact answer.
The real answer? Ask someone who really knows. Because it’s what they do.
4. Typical hot water system sizes in Australia
Let’s take a look at some of the most common hot water system sizes you’ll see on the market:
Electric storage: 25L to 400L
Gas storage: 90L to 300L
Gas continuous flow: Rated in litres per minute (L/min) – common sizes include 16, 20, and 26L
Heat pump: Usually 160L to 315L
Solar (with booster): 250L to 400L+.
At this point, it’s worth noting that hot water system sizes Australia-wide are generally quoted by tank capacity (in litres) or flow rate, depending on the type.
5. Real-world examples: Matching size to household
Still wondering what size hot water system do I need for a family of 5? In most cases, a storage system between 250-400L or a 26L/min continuous flow unit will suit a larger household. You’ll want something that can keep up with multiple morning showers, dishwashing, and laundry without lag.
For a medium-sized home, the question might be what size hot water system for family of 4 is right. Here, a 160-250L electric or gas storage tank is usually sufficient, or a 20-24L/min continuous flow system depending on usage.
Smaller households might ask what size hot water system do I need for a family of 2. If you’re using water efficiently, a 100-160L electric tank or a compact continuous flow system could be all you need – just make sure it aligns with how often you shower, use the washing machine, and so on.
6. Don’t forget recovery time And off-peak tariffs
One of the reasons electric hot water system sizes can be seriously misleading is because the tank needs to store enough hot water to last through peak usage – especially if you’re on an off-peak tariff, where heating happens overnight. So, even if your household only uses 200L a day, you might need a 250L tank to avoid cold showers in the evening. Get it?
Gas storage systems recover faster, meaning they can often be smaller. But if you switch from electric to gas or to a heat pump, make sure you understand how recovery rate affects your hot water availability.
7. Numbers confusing you? Let’s break it down
You’ll come across terms like:
- Hot water unit sizes
- Hot water tank sizes.
These are all referring to storage systems. But then there’s hot water system size for the overall CAPACITY – including continuous flow types, which don’t use tanks at all!
Confused? Then there’s also all those sizing tools online – just try searching for hot water system size calculator and see if that clarifies your mind! Remember, these kinds of simple and basic tools never account for every factor, like:
- Pipe length
- Climate
- Fixture flow rates
- Water pressure.
They may not sound very important, but trust us – they all play a part.
So while basic or average hot water tank sizes Australia-wide may give you a rough range, there’s no substitute for real-world advice.
8. What size water heater do I need – Really?
Are you planning to:
- Grow your family?
- Add a second bathroom?
- Get a new spa bath?
Changes like this will affect your future hot water needs – and what you need from your hot water system.
Choosing a system that’s slightly larger than your current needs can save you the cost and hassle of upgrading later. But don’t go overboard! Excessive size leads to unnecessary running costs. It’s a delicate balance that we know how to navigate.
9. Final reminder – Size isn’t everything
Efficiency, reliability, installation cost, and energy source. It may sound insignificant, but it’s everything! A smaller, high-efficiency system may outperform a larger, less efficient one – especially in mild climates or homes with low to moderate usage. Are you starting to understand?
Just need help getting it right?
Still wondering what size system suits your household? The helpful, friendly, fully-licensed technicians at Fix-It Right Plumbing can absolutely help. With fully equipped vans and expert advice tailored to your needs, our Melbourne hot water plumbers, Canberra hot water specialists, and Geelong hot water experts are also ready to ensure you get a reliable, energy-efficient hot water system that suits your lifestyle. Reach out today!
