# Continuous Flow vs Gas Storage Hot Water | Perth

> Endless hot water or a gas storage tank? Compare running cost, space and peak demand to choose the right gas hot water system for your Perth home.

URL: https://perthhotwatersystem.com.au/guide/continuous-flow-vs-gas-storage-hot-water/
Last-Modified: 2026-08-10

Guides — Explainer

# Continuous Flow vs Gas Storage Hot Water

Endless hot water or a gas storage tank? Compare running cost, space and peak demand to pick the right gas hot water system for your Perth home.

Published 10 August 2026 · 5 min read

![A continuous flow gas unit and a gas storage tank shown together](/images/featured/a-continuous-flow-gas-unit-and-a-gas-storage-tank-.webp)

## Same fuel, two very different machines

If you have mains natural gas or LPG, you have two ways of turning it into hot water.

**Gas storage** burns gas to heat a tank of water and keeps it hot until you need it. Familiar, simple, and generally the cheaper of the two to install.

**Continuous flow**, also called instantaneous, has no tank at all. Open a hot tap and the unit fires, water passes through a heat exchanger, and it comes out at temperature for as long as you keep the tap running.

Both are good systems. The choice comes down to space, demand pattern and how much you value never running out.

![Continuous flow gas hot water unit on an exterior brick wall](/images/content/continuous-flow-gas-hot-water-unit-mounted-on-an-e.webp)

## The comparison

|  | Continuous flow | Gas storage |
| --- | --- | --- |
| Runs out | Never, but flow rate limits simultaneous outlets | Yes, once the tank is drawn down |
| Standby heat loss | None | Continuous, 24 hours a day |
| Space | Wall-mounted box, compact | Tank footprint on the ground |
| Upfront cost | $1,400 - $3,200 installed | $900 - $2,200 installed |
| Install complexity | Higher, often needs a larger gas line | Lower |
| Simultaneous outlets | Limited by L/min rating | Excellent up to stored volume |
| Typical lifespan | 15 - 20 years | 8 - 12 years |
| Ignition | Electronic, no standing pilot | Often a standing pilot on older units |
| Temperature control | Precise, controllers available | Set at the thermostat |

## The case for continuous flow

**It genuinely never runs out.** Long showers, back-to-back showers, filling a bath after two people have already showered. There is no reservoir to deplete, so there is no last-person-gets-cold problem.

**No standby losses.** A storage tank radiates heat through its walls every hour of every day and the burner cycles to top it up, whether anyone uses hot water or not. Continuous flow burns gas only while water flows. Over fifteen years that is a genuine saving.

**It gives you the side passage back.** Perth has a lot of homes where a cylinder occupies most of a narrow side setback. A wall-mounted unit the size of a small cupboard frees that up entirely.

**Longer service life.** No cylinder full of heated water corroding from the inside means continuous flow units commonly run 15 to 20 years against 8 to 12 for a tank. There is no anode rod to replace either.

**Precise temperature control.** Optional controllers let you set delivery temperature exactly, which is useful for bathrooms and kitchens with different needs.

## The case for gas storage

**Very high simultaneous demand.** A tank delivers its full stored volume at once. Three showers plus a dishwasher off a 170 litre gas storage unit is fine. Doing the same off a modest continuous flow unit is not, unless you have sized up substantially.

**Lower upfront cost.** Both the unit and the installation are cheaper. If the existing installation is gas storage and you are replacing like for like, it is the simplest and least expensive path.

**Simplicity.** Fewer electronics. No electrical supply required on some models, which matters in a blackout, since most continuous flow units need power for ignition and controls.

**Existing gas line capacity.** Continuous flow units have a much higher peak gas demand than a storage unit, because they have to heat water instantly rather than gradually. Older properties sometimes need an upgraded gas line to support one, which adds cost.

## Sizing: the part that decides satisfaction

This is where switching goes wrong.

Storage is sized in litres: roughly 135 to 170 litres of gas storage for a family of four, less than the electric equivalent because gas recovers faster.

Continuous flow is sized in litres per minute: around 16 L/min for one bathroom, 20 L/min for a typical two-bathroom family home, 26 L/min where showers genuinely overlap.

Swapping a 170 litre gas tank for a 16 L/min continuous flow unit on the basis that “it never runs out” is a recipe for disappointment. It never runs out, and it also cannot serve two showers at once.

Perth adds a wrinkle: achievable flow rate depends on how far the unit has to lift the inlet temperature, and mains water is noticeably colder in July than February. We size on the winter figure for that reason.

## Which should you choose?

Choose **continuous flow** if you want endless hot water, are short on space, have moderate simultaneous demand, and your gas supply can carry it.

Choose **gas storage** if you routinely run several outlets at once, want the lowest upfront cost, or are replacing like for like with no appetite for additional gas or electrical work.

We install, size and repair both across the Perth metro. See our 

gas hot water

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 page for what is involved, or our broader guide on 

storage versus continuous flow

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 which covers electric and solar options too.

FAQ

## Common questions

### Is continuous flow gas better than storage?

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For most Perth households, yes. It gives endless hot water, saves space and has no standby losses. Gas storage still wins where very high simultaneous demand is normal, since a tank can deliver its whole stored volume at once.

### Which gas system is cheaper to run?

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Continuous flow usually, because it avoids the standby heat loss a storage cylinder incurs 24 hours a day. Gas storage can close the gap on very high-usage households where the tank is drawn down constantly anyway.

### Do both need a compliant gas connection?

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Yes. Both must be installed and connected by a licensed gas fitter, with correct flueing and clearances, and both require a compliance certificate. Continuous flow units often need a larger gas line because of their higher peak demand.

### Still have a question?

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