Does continuous flow hot water ever run out?

No. A continuous flow unit heats water on demand as it passes through, so it never runs out no matter how many showers run back to back. This is its main advantage over a storage tank, which can empty during heavy simultaneous use.

Is storage or continuous flow cheaper?

Storage units, particularly electric, are usually cheaper to buy and install. Continuous flow costs more upfront but often lasts longer, around 15 to 20 years versus 10 to 12 for a tank, so the lifetime cost can even out.

Which lasts longer, continuous flow or storage?

Continuous flow generally lasts longer, commonly 15 to 20 years, because there is no storage tank to corrode internally. Storage tanks typically last 10 to 12 years before internal rust leads to leaks and replacement.

Is continuous flow better for a small home or unit?

Often yes. Continuous flow units are compact and wall mounted, so they suit units and smaller Sydney homes with limited space. A storage tank needs a larger footprint either inside or outside the home.

Does continuous flow hot water ever run out?

No. A continuous flow unit heats water on demand as it passes through, so it never runs out no matter how many showers run back to back. This is its main advantage over a storage tank, which can empty during heavy simultaneous use.

Is storage or continuous flow cheaper?

Storage units, particularly electric, are usually cheaper to buy and install. Continuous flow costs more upfront but often lasts longer, around 15 to 20 years versus 10 to 12 for a tank, so the lifetime cost can even out.

Which lasts longer, continuous flow or storage?

Continuous flow generally lasts longer, commonly 15 to 20 years, because there is no storage tank to corrode internally. Storage tanks typically last 10 to 12 years before internal rust leads to leaks and replacement.

Is continuous flow better for a small home or unit?

Often yes. Continuous flow units are compact and wall mounted, so they suit units and smaller Sydney homes with limited space. A storage tank needs a larger footprint either inside or outside the home.

Hot Water

Continuous flow vs storage hot water: which should you choose?

By Terry, licensed plumber (Lic L10959) · 15 April 2026 · 5 min read

Quick answer

Continuous flow heats water only as you use it and never runs out, making it ideal for busy households and small spaces. Storage systems keep a tank of hot water ready, which suits homes with steady demand and off peak power. Continuous flow lasts longer but costs more upfront, so the right choice depends on your household and setup.

Continuous flow vs storage hot water: which should you choose? - Terry's Plumbing, Berala

When it comes time to replace a hot water system, one of the first decisions is continuous flow or storage. Both do the same job in different ways, and each suits different homes. Terry has installed plenty of both across Berala and Western Sydney since 1986, so here is a plain comparison to help you choose.

How each one works

A storage system keeps a tank of water heated and ready, usually 125 to 400 litres. When you open a hot tap, heated water flows out and cold water refills the tank to be heated again.

A continuous flow system, also called instantaneous, has no tank. It heats water on demand as it passes through the unit, only when a hot tap is running. Most run on gas, though electric versions exist.

Running out of hot water

This is the biggest practical difference. A storage tank can run out if several people shower in a row and it cannot reheat fast enough, leaving the last person with a cold shower. A continuous flow unit never runs out, because it heats endlessly on demand. For a busy family, that is a real advantage.

Space

Continuous flow units are compact and mount on a wall, which is handy for units and smaller Sydney homes with little space. A storage tank takes up a decent footprint, either inside or out.

Running cost

Continuous flow avoids standing heat loss, since there is no tank sitting hot all day, so it can be more efficient. Storage on off peak power can be cheap to run because it heats overnight when power is cheaper. The best value depends on your energy setup.

Upfront cost

Storage units, especially electric, are generally cheaper to buy and install. Continuous flow costs more upfront but tends to last longer.

Lifespan

Storage tanks last about 10 to 12 years before internal corrosion catches up with them. Continuous flow units often reach 15 to 20 years, since there is no tank to rust.

Which should you choose

Busy household that runs out of hot water: continuous flow, so it never runs dry
Limited space or a unit: continuous flow, for the compact wall mounted design
Off peak electricity and steady demand: a storage tank can be very economical
Lowest upfront cost: electric storage

Gas safety note

Most continuous flow units run on gas, so installation must be done by a licensed gas fitter with a compliance certificate under AS/NZS 5601. Terry holds licence L10959 covering gas fitting, so he can supply, install and certify the unit in one visit.

The right answer really does depend on your home, so Terry is happy to look at your setup and give honest advice plus a fixed quote before any work. Call Terry on 0415 274 542.

Frequently asked questions

Does continuous flow hot water ever run out?: No. A continuous flow unit heats water on demand as it passes through, so it never runs out no matter how many showers run back to back. This is its main advantage over a storage tank, which can empty during heavy simultaneous use.
Is storage or continuous flow cheaper?: Storage units, particularly electric, are usually cheaper to buy and install. Continuous flow costs more upfront but often lasts longer, around 15 to 20 years versus 10 to 12 for a tank, so the lifetime cost can even out.
Which lasts longer, continuous flow or storage?: Continuous flow generally lasts longer, commonly 15 to 20 years, because there is no storage tank to corrode internally. Storage tanks typically last 10 to 12 years before internal rust leads to leaks and replacement.
Is continuous flow better for a small home or unit?: Often yes. Continuous flow units are compact and wall mounted, so they suit units and smaller Sydney homes with limited space. A storage tank needs a larger footprint either inside or outside the home.
Does continuous flow need gas?: Most continuous flow units run on gas, though electric versions exist. Gas installs must be done by a licensed gas fitter with a compliance certificate under AS/NZS 5601. Terry, licence L10959, can supply, install and certify a continuous flow unit.

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Terry's been sorting plumbing across Berala and Western Sydney since 1986. Call 0415 274 542 for a straight answer and a fixed price.

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NSW Licence L10959 · 40+ years experience