How Many Litres Per Minute Does a Family Actually Need?
Hot water flow rate in litres per minute: the number on the box is not the number in your shower in July. Here is the one that is.
A typical Australian family needs a hot water flow rate of about 18 litres per minute: two standard showers at 9 litres a minute each, running at the same time. A couple in a one bathroom house gets by on 9 to 13 litres a minute. A family of five with a rain shower and a teenager who lives in the bathroom needs 24 or more. Work out what runs at once, add up the litres, then check what the heater can actually deliver in winter. That last step is where most people get it wrong.
Want your exact size? Our instant hot water sizing calculator works out the kW or litres a minute you need in winter, checks single or 3-phase power, then shows the units that fit.
Hot water flow rate by outlet
A standard shower uses about 9 litres a minute, a basin about 4 and a kitchen sink about 6. Those are the numbers to add up. Everything else in this article is built on this table.
| Outlet | Typical flow | Typical temperature at the outlet |
|---|---|---|
| Water saving showerhead | 7 L/min | 40°C |
| Standard showerhead | 9 L/min | 40°C |
| High flow or rain showerhead | 12 L/min or more | 40°C |
| Bathroom basin | 4 L/min | 38°C |
| Kitchen sink | 6 L/min | 45°C |
| Laundry tub | 8 L/min | 40°C |
Not all of that flow is hot water. A shower at 40°C is a mix of hot and cold. But a continuous flow or instantaneous heater has to lift the whole stream to 40°C, so for sizing you count the full mixed flow. Simple and slightly conservative. Good.
How to measure your own shower flow rate
The fastest way to measure shower flow rate is a bucket and a phone stopwatch: time how long the shower takes to fill a 10 litre bucket, then divide 600 by the seconds. 60 seconds is 10 litres a minute. 40 seconds is 15.
Do it with the shower on full hot, not mixed, so you are measuring the head and not your mixer. Most modern showerheads land between 7 and 9 litres a minute because a 3 star WELS head is capped at 9. Old heads and rain heads do not play by those rules. We have seen 18 litres a minute out of a big square rain head, which is one shower eating a whole gas unit.
Litres per minute for common Australian households
A one bathroom household needs 9 to 13 litres a minute, a two bathroom family needs about 18, and a busy three bathroom house needs 24 or more. The table assumes standard 9 litre heads. Swap in your measured numbers if you have them.
| Household | What realistically runs at once | Flow needed |
|---|---|---|
| Single or couple, 1 bathroom | 1 shower, sometimes the kitchen sink | 9 to 15 L/min |
| Family of 3 or 4, 1 bathroom | 1 shower plus kitchen or laundry | 15 to 17 L/min |
| Family of 4, 2 bathrooms | 2 showers | about 18 L/min |
| Family of 4 or 5, 2 bathrooms, busy mornings | 2 showers plus kitchen sink | about 24 L/min |
| 3 bathrooms or a rain shower in the mix | 2 or 3 showers plus a tap | 24 to 30 L/min |
Be honest about the "at once" column. The number of bathrooms does not matter. What matters is how many of them are in use at 7am on a school day. Plenty of three bathroom houses only ever run one shower at a time because there are two people living in them.
Why a heater's rated flow drops in winter
A continuous flow heater's litres per minute rating falls in winter because the cold water coming in is colder, so the burner or element has to lift each litre further. The heater's power is fixed. More temperature rise means fewer litres.
Gas units are rated at a 25 degree rise. Lifting Sydney winter mains water at about 13°C to a 40°C shower is a 27 degree rise. Melbourne is about 30. Canberra is about 33. So a 20 litre gas unit is not a 20 litre unit in July anywhere south of Brisbane.
| Winter, heating to 40°C | 20 L/min gas (Midea M20) | 26 L/min gas (Midea M26) | 28 kW electric, 3 phase |
|---|---|---|---|
| Brisbane, mains about 16°C | about 20 L/min | about 27 L/min | about 17 L/min |
| Sydney, mains about 13°C | about 18.5 L/min | about 24 L/min | about 15 L/min |
| Melbourne, mains about 10°C | about 16.7 L/min | about 22 L/min | about 13 L/min |
Winter flow figures are estimates from typical mains temperatures. Your local supply will vary by a degree or two.
Now put the two tables side by side. A two shower family needs about 18 litres a minute. In Melbourne a 20 litre gas unit gives 16.7. That is the July phone call we get every year: "the second shower goes cold". The heater is not broken. The heater is undersized.
20L vs 26L continuous flow: which one a family needs
A family that runs two showers at once needs a 26 litre continuous flow unit in Sydney, Canberra, Melbourne, Adelaide or anywhere with a real winter, and can use a 20 litre unit in Brisbane and further north. That is the whole decision for most homes.
- Midea M20, 20 L/min: $749. One shower anywhere, two showers in warm climates.
- Midea M26, 26 L/min: $849. Two showers anywhere in Australia, with room for the kitchen tap in most cities.
Prices current as of October 2026, AUD including GST, unit only. Installation not included.
The gap is $100. Nobody has ever rung us to say they regret the bigger unit. The only real reason to pick the 20 litre unit in a cold city is a gas line or meter that cannot feed 200 MJ/h, and your gas fitter checks that before anything is ordered.
What electric instantaneous heaters deliver in litres per minute
The biggest electric instantaneous heater for a house, 28 kW on 3 phase power, delivers about 13 to 17 litres a minute of 40°C water in winter, which is one good shower, not two. Single phase electric tops out at 9.5 kW, which is about 5 litres a minute in a Sydney winter: a kitchen sink or a basin, not a shower.
| Electric unit | Power supply | Sydney winter flow at 40°C | Realistic job | Price |
|---|---|---|---|---|
| Stiebel Eltron DHC-E 8/50 | Single phase, 9.5 kW | about 5 L/min | One sink or basin | $915 |
| Stiebel Eltron DEL 18 Plus | 3 phase, 19.4 kW | about 10 L/min | One shower, warm climate | $1,365 |
| Stiebel Eltron DEL 27 Plus | 3 phase, 28 kW | about 15 L/min | One shower anywhere | $1,399 |
| Stiebel Eltron DHE 27 | 3 phase, 28 kW | about 15 L/min | One shower anywhere, up to 60°C | $1,545 |
Prices current as of October 2026, AUD including GST, unit only.
3 phase units need a 3 phase supply at the switchboard. If your house does not have one, a 3 phase electric unit is off the table until the network upgrades your connection, and that is rarely cheap. Our guide to single phase vs 3 phase instant hot water explains how to check.
Electric instantaneous is excellent for one bathroom, a granny flat or a single outlet. It is not a whole family solution for two showers at once. Gas does that job. The full trade off is in our electric vs gas instantaneous hot water comparison.
Three ways families get the flow rate wrong
Families most often get the hot water flow rate wrong by sizing to the box rating instead of winter output, by forgetting the rain shower, and by counting bathrooms instead of showers that run together.
- Sizing to the box. A 20 litre rating is a 25 degree rise figure. Winter in most capitals needs more rise than that, so the real flow is lower.
- The rain shower. One 12 to 18 litre rain head can use most of a 20 litre unit by itself. If a renovation adds one, the hot water unit may need to go up a size too.
- Counting bathrooms. Four bathrooms and two residents is a one shower house. Two bathrooms and three teenagers is a two shower house plus a dishwasher.
There is also the low end. Gas continuous flow units need a minimum flow to fire, around 2.5 litres a minute on the Midea range. A dribbled basin tap may not light the burner. That is normal, and a reason not to buy a gas unit for a single basin. Our instantaneous hot water sizing guide covers matching units to single outlets.
Frequently asked questions
How many litres per minute of hot water does a family need in Australia?
A typical Australian family with two bathrooms needs about 18 litres per minute of hot water, enough for two standard 9 litre showers at once. Add about 6 litres a minute if the kitchen sink often runs at the same time, and more again for a rain shower.
What is a normal shower flow rate in Australia?
A normal shower flow rate in Australia is 7 to 9 litres per minute, because a 3 star WELS rated showerhead is capped at 9 litres a minute. Older showerheads and rain heads commonly run at 12 to 18 litres a minute.
Is a 20 litre continuous flow hot water system enough for a family?
A 20 litre continuous flow hot water system is enough for a family in Brisbane and warmer climates, but in a Sydney winter it only just covers two showers, and in Melbourne it drops to about 16.7 litres a minute, which is less than two showers need.
Should I get a 20L or 26L continuous flow hot water system?
Get a 26 litre continuous flow hot water system if your household runs two showers at once anywhere south of Brisbane, and a 20 litre unit if you mostly run one shower at a time or live in a warm climate. The Midea M26 costs $100 more than the M20 as of October 2026.
How many litres per minute does an electric instantaneous hot water system give?
A 28 kW 3 phase electric instantaneous hot water system gives about 13 to 17 litres per minute of 40°C water in winter, enough for one shower. A 9.5 kW single phase unit gives about 5 litres per minute in a Sydney winter, enough for a sink or basin only.
Get the flow rate checked before you buy
Send us your suburb, the showers that run at the same time and whether you have gas or 3 phase power. We will tell you the litres per minute you need and the unit that delivers it in winter. Browse the full instant hot water systems range or the Stiebel Eltron electric range.
Ask us what flow rate your home needs →
This guide is general information for Australian households and is not a substitute for advice on your specific home and site. Flow rates and winter output are estimates based on typical outlet flows and mains water temperatures, and will vary with your local supply and fixtures. Gas continuous flow units must be installed by a licensed gas fitter and plumber. Electric instantaneous units must be installed by a licensed electrician, and 3 phase units need a 3 phase supply. Confirm final sizing, gas supply, electrical capacity and installation costs with us or your installer before you buy.