We’ll help you choose the right hot water system for your home by comparing on‑demand units and tank models, so you know which suits your household’s energy, cost and space needs.
On‑demand units heat water only when a tap runs, saving energy and taking up little wall space. Tank systems keep a reserve of hot water ready and often cost less up front, but they use energy to maintain temperature and need more room.
Nearly two‑thirds of Australian homes still use tanks, while on‑demand units make up about 25% of installations. We’ll walk through energy use, peak demand, installation time, maintenance and long‑term cost so you can match a system to your routine.
For urgent advice or a rapid install in Melbourne, call us—OnCall Emergency Plumbers—available 24/7 on 1800 571 216. We use reputable brands and quality materials to get hot water back on fast.
Key Takeaways
- On‑demand units save energy and suit tight spaces.
- Tanks give immediate hot water and handle short outages.
- Upfront cost often favours tanks; long‑term energy savings can favour on‑demand.
- Match system capacity to household demand for best performance.
- Local factors in Melbourne — gas access, tariffs and wall‑mount opportunities — matter.
- Call us 24/7 on 1800 571 216 for fast, quality advice and installs.
Hot water systems in Australia today: what homeowners need to know
Many households in Australia replace like‑for‑like, but there are clear reasons to reconsider your water system at upgrade time.
Market snapshot: about two‑thirds of homes use a tank model while roughly 25% now choose on‑demand units. Tanks remain common because they are easier to install and suit gas, electric or solar connections.
Instantaneous units are gaining ground thanks to slim wall‑mount designs and energy savings from heating only when a tap runs. They are rated by litres per minute and suit smaller blocks, townhouses and units.
Regulations affect placement. Drain lines from temperature/pressure relief valves must discharge lawfully, and gas units need ventilation and clearances. Electric tanks can use off‑peak tariffs for cheaper running costs.
| Feature | Tank model | On‑demand unit | Installation notes |
|---|---|---|---|
| Space | Larger footprint | Slim wall‑mount | Check outdoor placement and venting |
| Energy use | Standby loss, tariff benefits | Heat on demand | May need gas line or switchboard upgrade |
| Compliance | Relief valve drain required | Ventilation and clearance rules | Plan early to avoid rework |
We serve Melbourne 24/7 for honest advice and affordable options. Call us on 1800 571 216 if you need urgent help or a tailored recommendation for your water heaters.
How hot water systems work: storage tanks vs continuous flow
Understanding how each system produces and delivers hot water makes it easier to match a unit to your household needs.
Storage hot water system fundamentals
A typical hot water tank heats water with a gas burner or an electric heating element inside an insulated cylinder. Cold water enters at the base and heated water rises to the top for use.
Systems hold roughly 25–400 L and usually keep stored hot water near 60°C to reduce bacterial risk. A tempering valve mixes down to ~50°C at the outlet for safety.
- Key parts: cylinder, heater or burner, thermostats, pressure relief valves and a sacrificial anode.
- Why anode matters: it corrodes to protect the tank and needs replacement over time.
- Performance: draw‑off rate and recovery time decide if the tank meets peak demand.
Instant operation and on‑demand heating
Instant hot water units detect when a tap opens using a flow sensor and fire a burner or element to push water through a heat exchanger. They heat only while you run a fixture, so there is minimal standby loss.
Manufacturers rate these units by litres per minute (commonly 12–27+ L/min), which tells you how many taps can run at once. Gas models need correct ventilation and clearances to meet code.
| Feature | Typical rating | Common issue |
|---|---|---|
| Output | 12–27+ L/min | scale in heat exchanger |
| Control | Precise outlet temperature | sensor faults or delays |
| Installation | Wall‑mount, gas or electric feed | ventilation or gas line upgrades |
We diagnose faults in both tank and on‑demand units, replace worn anodes and valves, and can upgrade gas lines. Call OnCall Emergency Plumbers across Melbourne for like‑for‑like installs or changeovers using reputable brands.
Continuous flow vs storage: pros and cons at a glance
This quick summary highlights practical strengths and trade‑offs between tank units and instant hot models.
Storage hot water: main pros
Immediate hot water at the tap and generally stronger initial pressure.
Lower upfront cost for many models and broad energy options — gas, electric or solar.
Storage hot water: main cons
Stored water loses heat over time, which raises running energy use.
Tanks need more space, regular anode and valve maintenance, and can corrode or leak if ignored.
Instant hot systems: main pros
Compact size and wall‑mount designs save room. They heat on demand, so you save energy over the year.
Parts are often modular, helping long‑term servicing and potential savings.
Instant hot systems: main cons
Higher upfront and installation cost and need correct gas or electrical services.
Output is rated in L/min, so poor sizing can limit simultaneous use and may cause a short delay to temperature.
- Pressure & capacity: tanks usually feel stronger at the tap; instantaneous units depend on sizing.
- Running costs: standby loss for tanks versus usage‑based heating for on‑demand models.
- Site check: we recommend a quick assessment to confirm meter capacity, ventilation and legal discharge paths.
| Feature | Tank | Instant hot |
|---|---|---|
| Upfront cost | Typically lower | Higher, plus install works |
| Running profile | Standby losses | Usage based heating |
| Space | Bulk, needs location | Wall‑mount, compact |
| Maintenance | Anodes, valves, tank checks | Heat exchanger, sensors |
We install reputable brands that balance cost and performance and service both system types 24/7 across Melbourne. For fast help and an honest recommendation call 1800 571 216.
Energy efficiency, heat loss and running costs
How you heat water has a big effect on your energy bills and comfort each day.
Heat loss in tanks and why tariffs and insulation matter
Water kept in a tank loses temperature through the cylinder and pipework. Even well‑insulated tanks need energy to maintain a 60°C setpoint required for health reasons.
Tempering valves mix hot water down to about 50°C at the tap, so you stay safe but the system still expends energy to keep water hot around the clock.
On‑demand heating and reduced standby energy in on‑demand units
Heating only when a tap runs eliminates most standby losses and often improves day‑to‑day energy efficiency. These units let you set outlet temperature directly and can lower running cost for typical household use.
Gas vs electric considerations for Australian households
Gas hot water can be cheaper where gas prices favour it, but gas units need ventilation and clearances. Electric options pair well with off‑peak tariffs or solar to reduce cost.
| Aspect | Electric tank | On‑demand electric | Gas on‑demand |
|---|---|---|---|
| Standby heat loss | High (unless well insulated) | Minimal | Minimal |
| Tariff benefits | Off‑peak heating reduces running cost | Limited unless paired with storage | Dependent on gas price |
| Installation issues | Tempering valve, space | Dedicated circuit, possible switchboard work | Ventilation, gas meter checks |
We size systems to avoid overspend, advise on pipe insulation and time‑of‑use strategies, and offer 24/7 service in Melbourne on 1800 571 216.
Sizing, water demand and installation constraints
Choosing the right size and site for a hot water system starts with measuring peak water use. We review household patterns, then match a tank or on‑demand unit to your needs. This prevents run‑outs and keeps bills sensible.
Matching capacity to demand: litres in tanks vs litres per minute
We size tanks by litres to cover peak showers and appliance draws. Small properties may need 25–50 L; family homes often use 135–315 L tanks.
Instant units are chosen by litres per minute. A one‑bath dwelling may be fine with 12 L/min. Larger homes often need 24–27+ L/min to handle simultaneous use.
Space and placement: outdoor, wall‑mount, ventilation and drainage requirements
Wall‑mount units free yard space, while tanks need room for access and valves. Gas appliances require clearances and ventilation. Regulations force relief valve drains to lawful discharge points.
Pressure, flow rate and low‑flow fixtures: real‑world performance
Minimum flow thresholds can stop ignition on some units. Low‑flow showerheads may affect temperature ramp. We check incoming water pressure, gas capacity and pipe runs before any installation.
- Practical tip: we may recommend multiple smaller units, a larger tank, or a hybrid to match peak demand without oversizing.
- Need help? For urgent sizing and compliant installs call our team or see hot water repairs Reservoir.
| Constraint | Tank | Instant unit |
|---|---|---|
| Typical sizing | 25–400 L | 12–27+ L/min |
| Space | Bulky, needs access | Wall‑mount, compact |
| Installation checks | Drain, tempering valve | Gas meter, ventilation, circuit |
Cost, lifespan and maintenance over the years
Understanding upfront price and long‑term care helps you pick the right hot water system. We explain typical outlays, retrofit complexities and routine tasks that prevent failures.
Upfront price, installation variables and retrofitting
Tank models usually have lower purchase and install fees. Instant units cost more and can need extra work when switching from a tank.
- Common cost drivers: relocating the unit for compliance, legal drain for a relief valve, gas line upgrades or a new electrical circuit for a heater.
- Retrofitting: expect added labour if ventilation or meter work is required.
Servicing considerations and expected lifespan
Routine maintenance keeps systems running and protects warranties. For tanks, we check anodes, valves and flush the cylinder. For on‑demand units, we descale and clean filters to protect the heat exchanger.
| Item | Tank | Instant unit |
|---|---|---|
| Typical lifespan (years) | 10–15 years | Up to ~20 years |
| Key maintenance | Anode checks, valve inspection, flushing | Descale, filter clean, heat exchanger checks |
| Warranty norms | Cylinders 7–12 years | Heat exchangers ~10–12 years |
We keep costs transparent and schedule maintenance to avoid surprise leaks or bursts. We use reputable brands and quality parts, and offer 24/7 Melbourne service for repairs, retrofits and replacements. Call 1800 571 216 for immediate help with no hot water or a failed tank.
Need help fast? OnCall Emergency Plumbers can specify and install the right hot water system
When hot water fails, fast, local support can make the difference between a short delay and a major household problem.
We offer 24/7 Melbourne emergency support for burst tanks, no hot water and urgent replacements. Our vans arrive stocked with parts so we can restore service quickly.
24/7 Melbourne emergency support for burst tanks, no hot water and urgent replacements
We assess your property and usage, then recommend a right‑sized hot water system—either a tank or an on‑demand unit—balancing comfort, efficiency and budget.
We handle the full installation, ensuring legal discharge for relief valves, verifying ventilation and clearances for gas appliances, and arranging any electrical or gas upgrades required.
Quality materials, reputable brands and affordable solutions — call 1800 571 216
- Rapid 24/7 response across Melbourne for no hot water, leaks and urgent replacements.
- Work with reputable brands and quality materials for reliable performance and fast repairs.
- Clear advice on running costs, tariffs for electric tanks and savings from on‑demand units.
- Post‑install maintenance plans: anode checks, valve service and heat exchanger descaling.
| Service | What we check | Benefit |
|---|---|---|
| Emergency call‑out | Fault diagnosis, temporary fixes, parts on‑board | Fast restoration of hot water |
| System specification | Sizing (25–400 L or 12–27+ L/min), site checks | Right capacity for household demand |
| Full installation | Relief valve discharge, ventilation, electrical/gas upgrades | Compliance and safe operation |
Call us now on 1800 571 216 or visit https://oncallemergencyplumbers.com.au/ for 24/7 advice, booking and rapid hot water system service in Melbourne.
Conclusion
We recommend choosing a hot water system that matches your household’s peak needs, available space and long‑term budget. There is no one‑size‑fits‑all answer.
Storage hot water and hot water tanks give strong multi‑outlet delivery but incur standby heat loss and ongoing maintenance. An instant hot unit saves energy and suits tight sites, but must be sized by litres per minute and may need a dedicated circuit or gas upgrade.
Factor total cost over the years, check compliance for relief valve discharge and gas ventilation, and right‑size to cope with Melbourne’s colder incoming cold water. We can inspect your installation and advise repair or replacement.
For tailored help or urgent service in Melbourne call us 24/7 on 1800 571 216.
FAQ
What are the main differences between continuous flow and storage hot water systems?
Continuous flow units heat water on demand using a heat exchanger and flow sensor, so they avoid tank standby losses and are compact. Storage systems hold a volume of heated water in a tank with a burner or electric element; they provide immediate supply but lose heat over time and need more space. We evaluate energy use, space, installation complexity and household demand when recommending a system.
Which hot water system is more energy efficient for an Australian home?
On‑demand systems generally use less energy because they eliminate standby heat loss from a tank. However, efficiency depends on usage patterns, fuel type and unit rating. For homes with low-to-moderate hot water use, we often find on‑demand units save more. For large households with simultaneous demand, a well‑insulated tank system with a high star rating can still be economical.
How do storage hot water systems work and what components should we monitor?
A storage system uses a tank, heating element or gas burner, thermostatic valves and a sacrificial anode to limit corrosion. We recommend checking insulation, pressure relief valves and the anode regularly. Poor maintenance increases heat loss, corrodes the tank and shortens service life.
How does an instant on‑demand unit operate?
When a tap opens, a flow sensor triggers the burner or electric element and the heat exchanger raises water temperature instantly. We advise sizing the unit to the household’s peak litres‑per‑minute (L/min) demand to avoid temperature drop during high simultaneous use.
What are the pros of choosing a storage tank system?
Tanks deliver immediate hot water at multiple outlets, often cost less to buy, and can be fuelled by gas, electric or solar. They suit households that need simultaneous use and where upfront cost or simple installation is a priority.
What are the cons of storage systems we should consider?
Tanks suffer heat loss, require more floor or roof space, need regular maintenance and anode replacement, and can corrode over time. These factors raise running costs and can lead to premature replacement if neglected.
What advantages do on‑demand hot water systems offer?
They are compact, reduce standby energy use, offer long-term running cost savings for many homes and often deliver a continuous supply if sized correctly. They also take up less space and are easier to fit in smaller properties.
What are the limitations of on‑demand systems?
They cost more upfront and can require complex installation, especially for gas units needing adequate ventilation. They also have a maximum flow rate; simultaneous showers or high‑flow appliances may exceed capacity, causing temperature drop or short delay to hot water.
How does heat loss affect running costs and what can we do about it?
Tanks lose heat through the shell and fittings, increasing energy use to maintain temperature. Proper insulation, lower thermostat settings, and choosing high‑efficiency models reduce losses. Tariffs and time‑of‑use rates also influence operating cost, so we review those when advising clients.
Is gas or electric heating better for our household?
Gas often offers lower running costs for higher demand and faster recovery, while electric units are simpler to install and pair well with solar PV. We compare local gas availability, electricity prices, appliance efficiency and installation constraints to recommend the best option.
How do we size a hot water system correctly?
For tanks, we match litres to peak usage and number of simultaneous outlets. For on‑demand units, we size by required L/min and desired temperature rise. We assess family size, shower count, and appliance use to avoid undersizing or overspecifying a unit.
What installation constraints should we be aware of?
Consider ventilation, wall‑mounting space, drainage for pressure relief, and access for servicing. Gas units need flues and safety clearances. We inspect site conditions and advise on placement — outdoor, roof or inside — to ensure compliance and performance.
How do pressure and low‑flow fixtures affect real‑world performance?
Low water pressure can reduce output temperature and flow from an on‑demand unit. We recommend checking household pressure and fitting pressure‑boosting or flow‑restricting fixtures as needed to maintain consistent temperature and reduce waste.
What are typical costs, lifespan and maintenance needs?
Upfront price varies by model, fuel and installation complexity. Tanks are usually cheaper to buy but may last 8–12 years; on‑demand units often last 10–15 years with proper servicing. Regular tasks include anode inspection, valve checks, flushing tanks and servicing heat exchangers to extend life and efficiency.
Can we retrofit an on‑demand system where a tank currently sits?
Often yes, but installation may require gas line upgrades, extra ventilation, electrical capacity or changes to pipework. We assess the site, quote retrofit costs and outline any required permits or compliance work before proceeding.
What should we do in an emergency — burst tank or sudden loss of hot water?
Shut off the water supply and isolating valves, turn off power or gas to the unit, and call emergency plumbers immediately. We provide 24/7 emergency support in Melbourne for burst tanks, urgent replacements and temporary solutions to restore hot water safely.
Which brands and materials do we recommend for reliability?
We specify reputable brands with proven Australian support and parts availability. Stainless steel tanks, quality heat exchangers and certified gas components improve durability. We choose products that match the site, budget and expected service life.
How do we decide between short‑term cost savings and long‑term running costs?
We model lifetime costs, including purchase, installation, energy use and maintenance, and compare payback periods. For many households, slightly higher upfront investment in an efficient on‑demand unit pays off over time; for others, a tank may suit cashflow or installation simplicity.
Do solar systems pair well with either option?
Solar thermal integrates smoothly with tanks as pre‑heating, while solar PV can power electric tanks or boost heat pumps and some electric on‑demand units. We evaluate roof space, orientation and existing PV to recommend the best hybrid solution for lower bills and emissions.
