We get it. Few things are more frustrating than a cold shower halfway through your morning, or an energy bill that seems to climb every quarter. Hot water heating is one of the biggest energy costs in the average Australian home, so the system you choose matters.
In short, an instant hot water system heats water only when you turn on the tap. You don’t pay to keep a full tank hot around the clock.
How Does an Instant Hot Water System Work?
An instantaneous hot water system, also known as a continuous flow hot water system, has no storage tank. When you turn on a hot tap, the unit detects the water flow and heats it on the spot, then switches off when the tap closes. An instant gas hot water system does this with a gas burner and heat exchanger, while instantaneous electric hot water uses heating elements.
Gas water heaters generally deliver higher flow rates for larger households, while electric instant hot water can suit smaller homes or units without a gas connection.
6 Benefits of Installing an Instant Hot Water System
1. Long-Term Energy Savings
A traditional storage tank heats a full load of water and then keeps reheating it to hold its temperature, day and night, whether you use it or not. This is called standby heat loss, and it means you’re paying to heat water that sits unused. An instant hot water system avoids this completely. Because it only fires up when hot water is being drawn, the energy you pay for goes into water you actually use.
For most households, hot water is used in short bursts throughout the day, such as showers, dishes and washing. Heating water only at these moments is far more efficient than keeping 160 or more litres hot 24/7. Over the 15 to 20 year life of a system, the savings can be significant.
2. Lower Running Costs
Less wasted energy translates directly into lower gas or electricity bills. Gas hot water heaters sold in Australia carry an energy star rating, and many instant models sit at the higher end of that scale. Choosing a highly rated unit and sizing it correctly for your household are the two biggest factors in keeping running costs down. A system that is too large wastes money upfront, while one that is too small struggles to keep up.
3. Endless Hot Water
With a storage tank, the amount of hot water you have is limited by the tank’s size. Once it’s empty, you wait for it to reheat. A continuous hot water system has no such limit. It keeps heating for as long as the tap is running, which suits large families, households with teenagers and homes with guests.
How much hot water you can use at once depends on the unit’s flow rate, measured in litres per minute. A correctly sized instantaneous gas hot water unit can run two showers and the dishwasher at the same time without losing temperature.
4. Space-Saving Design
Storage tanks need a large patch of floor space, either outdoors or in a cupboard. Instant units are compact, roughly the size of a small suitcase, and mount directly on an external wall. This frees up room in courtyards, side passages and laundries, and makes them a practical choice for townhouses, units and smaller blocks.
5. Longer Lifespan
Storage tanks hold water constantly, which leads to internal corrosion over time. Most tanks last around 10 to 15 years before they need replacing. Because an instantaneous hot water system doesn’t store water, it avoids much of this wear. With regular servicing, many units can last up to 20 years, so you replace your system less often.
6. Precise Temperature Control
Many instant systems let you set the exact water temperature, often through a digital controller in the bathroom or kitchen. This means the water arrives at the temperature you choose rather than as hot as the tank allows. It’s more comfortable, avoids wasting energy on overheating water, and helps reduce the risk of scalding for children and older family members.
Instant Hot Water vs Storage Tank: At a Glance
| Feature | Instant hot water system | Storage tank system |
|---|---|---|
| How it heats | On demand, as water flows | Heats and stores a full tank |
| Standby heat loss | None | Ongoing, 24/7 |
| Hot water supply | Continuous | Limited to tank size |
| Space needed | Compact, wall-mounted | Large floor footprint |
| Typical lifespan | Up to 20 years | Around 10–15 years |
| Upfront cost | Can be higher | Often lower |
*The trade-off is worth knowing: an instant unit can cost more upfront, and you may wait a few seconds for hot water to reach the tap. For most households, the long-term savings outweigh both.
Is an Instant Hot Water System Right for You?
An instant hot water system is likely a good fit if you:
- Want to reduce long-term energy costs
- Regularly run out of hot water
- Have limited space for a storage tank
- Have an ageing tank that is due for replacement
South Australia also has rules on which water heaters can be installed in homes, and Adelaide’s water can be hard on heat exchangers over time. A licensed plumber can confirm which systems are compliant and suited to your property.
Instant Hot Water Brands We Install
SOS Plumbing and Gas installs, services and repairs instant hot water systems from a wide range of trusted brands. Instant gas hot water models are widely available across these brands, while electric instant hot water options vary by brand and model.
- Rheem is one of Australia’s most established hot water manufacturers, with a range of continuous flow gas models for homes of all sizes.
- Rinnai is widely known for its continuous flow gas systems and digital temperature controllers.
- Bosch offers compact, efficient instant gas hot water units suited to smaller spaces.
- Dux is a long-standing Australian brand offering gas and electric hot water solutions.
- Chromagen produces continuous flow gas systems alongside its solar and heat pump range.
- Vulcan provides reliable, value-focused hot water systems for budget-conscious households.
- Aquamax offers compact continuous flow units designed for everyday household use.
- Thermann is an Australian brand with a range of continuous flow gas water heaters.
Why Choose SOS Plumbing and Gas in Adelaide?
Choosing a new hot water system can feel overwhelming. Our job is to make it simple. As licensed Adelaide plumbers and gas fitters, we handle everything from start to finish:
- We recommend the right size and type for your household, not the most expensive unit
- We install safely and to code, and remove your old system
- We understand Adelaide homes, local water quality and SA regulations
- We provide ongoing servicing and repairs to keep your system running for years
Ready to Make the Switch?
Enjoy endless hot water and lower energy bills. Reach out to SOS Plumbing and Gas today for friendly, expert advice and a seamless instant hot water system installation.
FAQS
Is Instant Hot Water Cheaper to Run than a Storage Tank?
In most cases, yes. An instant hot water system only heats water on demand, so there’s no standby heat loss. That usually means lower running costs over time.
Is Instant Gas Hot Water or Electric Instant Hot Water?
Instant gas hot water suits larger households that need strong, simultaneous flow. Electric instant hot water can suit smaller homes or units without a gas connection. Our team will help you weigh up the options.
How Long Does an Instant Gas Hot Water System Last?
With regular servicing, an instant gas hot water system can last up to 20 years.
Can I Replace My Old Tank with an instant System?
Absolutely. We regularly swap storage tanks for continuous hot water systems across Adelaide, including any gas, plumbing or electrical changes required.