“What size hot water system do I need?” is an important question! Choose one that’s too small, and you’ll run out of hot water when you need it most. Go too big, and you’ll waste energy (and money!).
This guide will help you figure out the perfect fit so your home stays comfortable without blowing out your energy bills.
Key Takeaways
- Think about your household’s hot water usage—how many people live in your home, how many bathrooms you have, and daily activities like showers, dishwashing, and laundry.
- Learn about different hot water systems—electric, gas, solar, and heat pump systems—so you can choose one that’s energy-efficient and cost-effective.
- Consider key factors like hot water consumption, peak times, energy efficiency ratings, storage tank vs. continuous flow systems, and climate. This way, you’ll avoid running out of hot water or paying for a larger system than you need.
Table of Contents
Assessing Your Household's Hot Water Needs
Before choosing a hot water heater, it’s important to understand how much hot water your household actually uses.
Think about your daily routine—how many people live in your home? How many showers are taken each day? How often do you wash dishes or do laundry?
The more people and hot water outlets (like taps and showers) you have, the bigger your hot water system size needs to be.
You also want to plan for the future. If your family grows or you add another bathroom, you’ll need more hot water supply. Picking the right storage hot water or continuous flow system now can save you from running out later while keeping your energy bills in check.
Daily Hot Water Usage Per Person
On average, a person uses around 50 litres of hot water per day, but this can vary a lot. A 10-minute shower alone can use up to 105 litres, depending on your shower head and water flow. Washing machines and dishwashers also add to your daily hot water usage.
If you’re buying a new hot water system, don’t just look at the average use—think about how energy-efficient your appliances are. Choosing an efficient hot water system with the best energy efficiency rating can help you save money while still giving you enough hot showers for everyone in the house.
Peak Demand Times
Mornings are usually the busiest time for hot water—especially if multiple people are showering at the same time. This is called your peak demand. If your system isn’t big enough, you might run out of hot water before everyone’s had their turn.
For continuous flow systems, you need to think about how many hot water outlets (like taps and showers) could be running at the same time. The right water flow and hot water tank capacity will ensure you never have to deal with a surprise cold water blast!
If you’re using an electric storage hot water system, you may also want to consider off-peak times to save on electricity costs. Some homes with off-peak tariffs heat the water overnight, helping reduce energy bills while still providing plenty of hot water during the day.
Choosing the Right Type of Hot Water System
Picking the best hot water system for your home depends on a few things—how many people live there, how often you use hot water, and how much space you have. The main types of systems are electric, gas, solar, and heat pump models. Each one has its own benefits, so it’s important to find the right fit for your needs.
There are also two main ways these systems heat water: storage hot water systems, which keep a tank of pre-heated water ready to go, and continuous flow systems, which heat water on demand. If you’re looking to save money on energy bills, an efficient hot water system can make a big difference while also freeing up space in your home.
Hot water systems come at different price points depending on the type, size, and installation costs. Want to know the full cost breakdown? Check out how much a hot water system costs.
Electric Hot Water Systems
There are two main types of electric hot water systems: storage tank models and continuous flow systems.
Storage tank systems use an electric heating element to heat water and keep it ready in a hot water tank. While they’re reliable, they can be less energy-efficient since they keep heating the water all day.
The good news? Some models let you take advantage of off-peak electricity rates, which can help lower your running costs.
Continuous flow electric systems (also called instant hot water systems) heat water as you need it. This means they don’t need a storage tank, so you won’t lose heat from stored water. These systems are great for smaller households looking for an efficient hot water system that doesn’t take up much space.
Gas Hot Water Systems
Gas hot water systems are often cheaper to run than electric ones, especially if you have access to natural gas or liquid petroleum gas (LPG). There are two types:
- Storage gas systems keep a set amount of water hot in a storage tank using a gas burner.
- Continuous flow gas systems heat water only when you turn on the hot water tap, so you’re not paying to heat water you’re not using.
If you’re thinking about a continuous-flow gas system, you’ll need to consider how many hot water outlets (like showers and sinks) will be running at the same time. Choosing the right flow rate and installing a thermostat to control the temperature will help make sure you have enough hot water without wasting energy.
Installing a gas hot water system? Our licensed gas plumber in Melbourne can ensure it’s set up safely and efficiently.
Solar Hot Water Systems
A solar hot water system uses the sun’s energy to heat water, making it one of the most energy-efficient options available. If you live in a sunny area, this system can provide most of your hot water supply, reducing your reliance on electricity or gas.
Because solar systems rely on sunlight, they often come with a gas system or electric booster to make sure you still have hot showers on cloudy days or at night.
While the upfront cost of installing a solar system is higher, it can save you a lot of money on energy bills over time, making it a smart long-term investment.
Heat Pump Hot Water Systems
A heat pump hot water system is one of the most efficient hot water systems available. Instead of using electricity to heat water directly, it works like a reverse air conditioner, pulling heat from the air and using it to warm the hot water tank.
Although heat pump water heaters can cost more to install, they use much less electricity than regular electric water heaters, so you’ll save money on your energy bills in the long run. They work well in most climates and suit different household sizes, making them a great eco-friendly option.
Factors Influencing Hot Water System Size
Choosing the right-sized hot water system means getting enough hot water without wasting energy. A system that’s too small won’t keep up with your needs, while an oversized one will drive up your power bills. Finding the right balance ensures comfort and efficiency.
The size you need depends on:
- How many people live in your home (bigger families need bigger systems)?
- How much hot water do you use each day (long showers? Lots of dishes?)?
- Peak usage times (like everyone showering in the morning).
- Your home’s plumbing setup (water pressure and pipe layout can affect performance).
Choosing the right size means lower energy bills and better comfort for your household.
Climate and Geographic Location
Where you live plays a big role in choosing the right hot water system size.
- Colder climates need bigger systems because the incoming water is colder and takes longer to heat.
- Warmer areas can usually get by with smaller systems since the water starts off at a higher temperature.
If you’re in a chilly part of Australia, you might also need a more powerful heater to make sure you always have enough hot water.
Energy Efficiency Ratings
Hot water systems use a lot of energy, so picking an energy-efficient model can help you save on bills.
- Look for high-energy star ratings – the more stars, the better!
- Heat pump hot water systems are one of the most efficient choices and can run on cheaper electricity tariffs.
- Minimum Energy Performance Standards (MEPS) ensure that all hot water systems sold meet basic efficiency levels.
An efficient system can mean a smaller tank or a lower flow rate, which helps cut down on energy use and costs.
Cost Considerations
The price of a hot water system isn’t just about the upfront cost—you also need to think about running costs, maintenance, and repairs.
- Larger systems cost more to buy and install but might be necessary for bigger households.
- Solar hot water systems are more expensive upfront but can save you money in the long run with lower energy bills.
- Gas hot water systems are often cheaper to run than electric ones because they heat water quickly and efficiently.
Finding the right balance between budget and efficiency will help you choose a system that works best for your home without spending more than you need to.
If your system suddenly stops producing hot water, there could be a few reasons why. Read our guide on what to do if you have no hot water to troubleshoot the problem.
Sizing Guide for Different Hot Water Systems
Choosing the right-sized hot water system ensures you have enough hot water without wasting energy. The best size depends on the number of people in your home and your daily hot water habits.
Storage System (Tank-Based Systems)
Storage hot water systems supply hot water from a tank that heats and holds a set amount of water. A system that’s too small means you might run out of hot water, while an oversized one wastes energy.
General tank size guide:
- 1–2 people: 90–150L
- 3–4 people: 150–250L
- 5+ people: 250–400L
Here are some tips for choosing the right tank size:
- If multiple people shower at the same time, go for a larger tank.
- Some appliances, like dishwashers, use a lot of hot water—factor this into your choice.
- If you have a gas supply, gas storage systems heat water faster than electric ones.
Continuous Flow Systems (Tankless)
Continuous flow systems supply hot water only when needed, so you don’t have to worry about running out. Instead of tank size, these systems are measured by flow rate (litres per minute, L/min).
General flow rate guide:
- Small homes (1–2 bathrooms): 16–20L/min
- Medium homes (2–3 bathrooms): 20–26L/min
- Large homes (4+ bathrooms): 26L/min or more
Here are some things to consider:
- Gas-powered continuous flow systems heat water faster than electric ones.
- If your unit has a pilot light, check its efficiency—it can use extra gas when idle.
- Ensure your gas supply can meet the demand, especially for large households.
If you’re considering a heat pump system, make sure you choose the right size for your needs. Check out our heat pump hot water system sizing guide to find the perfect fit.
Calculating Temperature Rise
To get the right hot water system, you need to know how much it needs to heat up the water. This is called temperature rise, and it depends on the incoming cold water temperature and your desired temperature.
For example, if your tap water is 15°C and you want your hot water to be 48°C, your system needs to heat it by 33°C. The bigger the temperature rise, the more powerful your system needs to be.
Quick Tip: If you live in a colder area where the incoming water is colder, you might need a stronger system to heat it properly.
Planning for Future Needs
Your hot water needs today might not be the same in a few years. Think about:
- Growing family? More people means more hot water.
- Home extensions? Adding a bathroom or new fixtures increases demand.
- New appliances? A dishwasher or bigger washing machine can use extra hot water.
Upgrading later can be costly, so choosing a system that can handle future demand can save you money and reduce energy consumption in the long run.
Professional Assistance and Tools
Picking the right hot water system can be tricky, but you don’t have to do it alone.
- Use online calculators to estimate the best system size for your home.
- Talk to a plumber—they know what works best for your area and household.
- Ask retailers—they can help you compare different brands, sizes, and prices.
Getting professional advice ensures you pick the right system from the start—saving you money and hassle. Choosing the right hot water system can be tricky, but our hot water plumber in Melbourne can help you pick the best option and ensure a proper installation.
Summary
Choosing the right hot water system isn’t just about picking the right size—it’s about making sure it suits your home’s needs both now and in the future. You need to consider how much hot water your household uses daily, whether you live in a colder climate that requires a stronger system, and how energy-efficient your chosen system is. Each type—electric, gas, solar, or heat pump—has its own benefits, so it’s important to weigh up both the upfront cost and long-term savings.
Planning ahead can save you from costly upgrades down the track. If your family is growing, you’re adding extra bathrooms, or installing new appliances, choosing a system that can handle increased demand is a smart move.
It’s always worth seeking expert advice, whether from a plumber or a retailer, to ensure you get the best fit for your home. With the right system, you can enjoy reliable hot water while keeping energy costs under control.
Need help with installation or repairs? Our expert plumbing services in Melbourne at MGR Plumbing cover everything from hot water system installations to ongoing maintenance.
Frequently Asked Questions
How do I calculate the size of the hot water system I need?
The right size hot water system makes sure you have enough hot water without wasting energy. To work it out, think about how much hot water your household uses daily and when you use it the most (like mornings or evenings). You can also use an online water heater sizing calculator or ask a professional for advice to get the best recommendation for your home.
What are the benefits of solar hot water systems?
Solar hot water systems are great for saving money on power bills because they use the sun to heat your water. They’re an energy-efficient and eco-friendly choice, especially if you live somewhere with plenty of sunshine. Over time, they can pay for themselves by cutting down on electricity or gas costs.
Are gas hot water systems cheaper to operate than electric systems?
Yes! Gas hot water systems usually cost less to run than electric ones because gas is generally cheaper than electricity, and gas systems heat water faster. That means you can get away with a smaller system, which also helps keep running costs down.
How does climate affect the size of the hot water system I need?
If you live somewhere cold, your system has to work harder to heat the water because the incoming water temperature is much cooler. That means you’ll need a bigger system to keep up. But if you’re in a warmer area, a smaller system is usually enough since the water doesn’t need as much heating.
Why is it important to consider future household changes when selecting a hot water system?
Your home might not always stay the same! If you plan on having kids, getting a new housemate, or adding an extra bathroom, your hot water needs will increase. Choosing a system that can handle future demand can save you from expensive upgrades later, and make sure you don’t run out of hot water when you need it most!
