Choosing the right hot water system setup can feel like guesswork, especially when your only reference is the tepid trickle that runs cold halfway through your shower. So what size hot water system do I need, we hear you ask? The answer depends on more than just the number of people in your home.
There are a lot of hot water system sizes, and what also matters to choose the perfectly-sized one is:
- Lifestyle
- Water usage habits
- Your appliance setup.
So here’s a simple, realistic guide to help you figure out which size system suits your situation – whether you’re a busy family of five, a homebody couple, or a minimalist single who only showers on alternate days (no judgement).
1. Singles, students, and light users (1 person)
If you live alone and tend to have quick showers, a compact system will usually do the trick. For electric storage, a 50L to 80L unit is often enough. If you use an instantaneous or continuous flow system, look for models with a 16L/minute flow rate.
Gas or heat pump systems may seem like overkill for one person, unless energy efficiency is your top priority.
Relevant to you:
- Low daily usage
- May use cold wash for laundry
- Often live in small homes or units with space constraints.
What size hot water tank do I need? For most singles: 50-80L electric or 16L/min flow rate.
2. Couples and small households (2 people)
For two adults sharing a bathroom (and likely a dishwasher), you’ll need a bit more capacity. In most cases, a 125L to 160L electric tank will do fine.
If you’re using gas or solar, system sizing depends on the number of outlets in use at once, not just the people. That’s where hot water system sizes vary more – it’s about flow rate and recovery speed.
What size hot water system do I need for a family of 2? Roughly 125-160L (storage) or 18-20L/min (continuous flow).
3. The average family (3-4 people)
This is where things get serious. A family of four doing morning showers, running the dishwasher, and nightly laundry will need a larger system – especially if everyone showers back-to-back.
What size hot water system for family of 4? Most experts recommend at least 250L for electric storage systems or a continuous flow unit rated at 24-26L per minute.
Keep in mind:
- Solar with electric booster may need more panel area but gives better efficiency long term.
- Instantaneous systems are great if you have gas and don’t want to worry about running out.
- Larger hot water tank sizes need room – so check your installation space before committing.
4. Bigger families or high-demand homes (5+ people)
If you’re dealing with a household of five or more, or even just a few teenagers who treat the bathroom like a private retreat, you’ll need something with grunt.
What size hot water system do I need for a family of 5? A 300L electric storage tank is usually the minimum. For gas continuous flow, 32L/min units (or two smaller units in parallel) are often recommended.
Don’t forget about recovery rate – the time it takes to reheat a tank after it’s been drained. Gas and solar tend to recover faster than electric, which can matter if your family all showers morning and night.
Hot water system size really counts here, especially if you’re in a busy household using multiple outlets at once.
5. Eco-conscious households
If you’re trying to reduce your carbon footprint, a heat pump or solar hot water system is your best bet – but size still matters.
Solar systems in Australia usually range between 250-400L tanks with electric or gas boosters. In sunny areas like Sydney, you can often run most of the year without relying much on the booster at all.
Electric hot water system sizes vary based on climate and orientation – solar requires enough north-facing roof space, while heat pumps work best in warm to moderate climates.
6. Low-usage homes (weekenders, investors)
If your property isn’t in use daily, you don’t need a full-size tank. Instead, focus on energy efficiency and compact design.
For Airbnb or short-stay rentals, 80L to 125L tanks usually cover basic demand. Tankless or hot water heater sizes with adjustable flow rates work well for variable occupancy.
7. Busy modern homes with multiple bathrooms
Even with just 3 or 4 people, some households push systems to the limit because of multiple bathrooms, bathtubs, and dishwashers all running at once.
This is where hot water system sizes Australia can be deceiving – it’s not just about litres, but also simultaneous usage. If two people are showering while the washing machine and kitchen tap are also running, a standard unit may struggle.
In this case, you’re not just asking what size water heater do I need – you need to consider hot water delivery infrastructure, including pipe sizing and water pressure.
8. People who love long showers (you know who you are)
If you take 20-minute showers or have a large bath you fill regularly, upsize. A bath can use 100-150L in one go. Add that to any other usage, and your hot water tank size becomes critical.
You might also want a system with a fast recovery rate – heat pump, gas, or even a solar booster.
9. Households running hot-water appliances
Some setups – washing machines, dishwashers – use hot water directly instead of internal electric heating. If that’s you, allow for an extra 50L/day usage on average.
This affects hot water tank sizes, especially for electric systems with slow recovery rates. Instantaneous systems handle this better, especially in climates like Sydney where demand fluctuates with the weather.
10. Upgraders switching from tank to continuous flow
If you’re ditching an old tank and want the benefits of endless hot water, you’ll need to convert your mindset from litres to litres-per-minute. The unit size in this case doesn’t look like a tank at all, but flow rate is key.
What size hot water system do I need?:
- A flow rate of 24L/min is a good minimum for families
- 26-32L/min is better for large households or multi-bathroom setups.
Just remember: continuous flow doesn’t store water – it heats on demand. That makes them space-saving and energy-efficient, but they do require adequate gas supply and pressure.
A few quick answers for the curious
Q: What size hot water system do I need?
A: Depends on people + lifestyle + usage habits.
Q: What size hot water tank do I need?
A: For 1-2 people: 80-160L. For 3-4: 250L+. For 5+: 300L+.
Q: What size water heater do I need for instant?
A: If using continuous flow, match to 16-32L/min flow rate based on how many outlets may be running at once.
Need help choosing the right size hot water system in Sydney?
At Link Plumbing in Sydney, we’ve helped thousands of households find the right system for their needs. Whether you’re upgrading, downsizing or building new, we’ll recommend the best setup for your home and lifestyle – with upfront fixed pricing, no surprises.
Call today for expert advice and same-day service.
