Hot Water on Demand
Storage hot water systems heat water and hold it in tanks until needed. The water sits there, gradually losing heat through the tank walls, requiring reheating to stay ready. If you use all the stored hot water, you wait for more to heat. The tank takes space whether you need hot water or not.
Instant systems take a different approach. Water flows through a heat exchanger only when you demand it. Turn on a tap and the system activates. Cold water enters, passes through the heating element or gas burner, and emerges hot. Stop using water and the system stops heating. Simple and logical.
The advantages follow from this approach. No standby losses because nothing is kept hot. No running out because water is heated continuously as used. Compact size because no storage tank is needed. The system can mount on a wall inside or outside, freeing floor space for other purposes.
The technology has been common in Europe and Asia for decades. Australian adoption has increased as gas prices, electricity costs, and space constraints make the efficiency advantages more compelling. Modern units are reliable, efficient, and well-suited to typical household demands.
Gas vs Electric
Instant systems come in both gas and electric versions, each with distinct characteristics.
Gas instant systems dominate the market for whole-house applications. Natural gas or LPG burners heat water as it flows through the heat exchanger. They produce high flow rates capable of supplying multiple simultaneous uses. A shower running while someone uses the kitchen tap presents no problem for a properly sized gas unit.
Electric instant systems suit specific applications rather than whole-house supply. The electrical load required for high flow rates exceeds what standard household circuits can provide. Point-of-use electric units work well for single outlets like a kitchen sink or bathroom basin, but can't match gas systems' whole-house capability.
Running costs favor gas in most situations. Per-unit energy costs make gas heating cheaper than electric resistance heating. The efficiency advantages of instant over storage apply to both fuel types, but gas instant remains more economical than electric instant for typical usage.
Installation requirements differ significantly. Gas systems need gas supply connections and flue systems for exhaust. Electric systems need appropriate electrical circuits but no gas or ventilation. The existing infrastructure affects which type suits each property.
Environmental considerations are evolving. Gas produces emissions at point of use while electric systems produce no on-site emissions. However, electricity generation still involves significant fossil fuel use. As the grid becomes greener, electric systems become environmentally better. Heat pump systems offer another path to reducing hot water emissions.
Sizing and Capacity
Choosing the right capacity instant system ensures adequate hot water without overspending on unnecessary capability.
Flow rate matters more than tank size for instant systems. Capacity is measured in litres per minute that can be heated to the desired temperature rise. A 26 litre per minute system handles more simultaneous demand than a 16 litre per minute one.
Temperature rise affects effective capacity. Heating cold winter water to shower temperature requires more energy than heating summer water. The same system delivers higher flow rate in summer than winter because the temperature difference is smaller.
Simultaneous use patterns guide sizing decisions. A household where two people might shower simultaneously needs more capacity than one where only one shower runs at a time. Consider realistic usage scenarios rather than theoretical maximums.
Canberra's cold inlet water temperatures in winter matter. Cold water entering at 10 degrees or below requires more heating than water entering at 20 degrees. Systems rated for mild climates may underperform in Canberra winters.
Water-efficient fixtures reduce flow requirements. Low-flow shower heads and tap aerators decrease the flow rate needed to supply your house. This can allow a smaller, less expensive system to meet your needs.
Installation Requirements
Installing instant hot water involves specific requirements that affect placement and cost.
Gas connection must supply adequate flow. Instant systems have high gas demands when operating. Undersized gas lines restrict flow and affect performance. Upgrading gas supply may be necessary when installing larger units or where existing supply is marginal.
Flue requirements for gas units vary by installation type. External units often use natural draft fluing. Internal units typically need powered flues with specific clearance requirements. Installation position must allow compliant fluing.
Electrical connection powers controls and ignition even on gas units. The electrical load is minimal compared to electric hot water systems but must be available at the installation location.
Water connections need appropriate sizing and pressure. Very low pressure may prevent systems from activating. Very high pressure needs regulating. Flow restrictors on some systems limit output if supply pressure is inadequate.
Location affects access for service and repair. Wall-mounted units need structural support. Clearances around the unit allow maintenance access. Weather protection matters for outdoor installations.
Converting from storage to instant often involves repositioning. Storage tanks are often located away from usage points. Instant systems work best closer to where hot water is used, reducing pipe runs and wait time. This relocation adds to conversion costs but improves performance.
Operating Characteristics
Understanding how instant systems behave helps set appropriate expectations.
Slight delay before hot water arrives is normal. The system must detect flow, ignite, and heat water. A few seconds pass before hot water reaches the tap. This delay is shorter than waiting for stored hot water to travel from a distant tank.
Minimum flow is required to activate heating. Very low flow rates don't trigger the system. Trickling a tap won't produce hot water. This prevents wasteful operation when flow is too low for useful hot water delivery.
Temperature stability depends on system quality. Better systems maintain consistent temperature despite flow variations. Economy systems may fluctuate more when flow changes. Premium systems with multiple burners or modulating elements provide steadier temperatures.
Cold water sandwich can occur when usage pauses briefly. Stopping and starting hot water use can produce bursts of cold water between hot. Systems with small buffers minimize this effect.
Simultaneous use affects temperature if demand exceeds capacity. Opening another hot water outlet while one is running divides the heated water between them. Properly sized systems handle expected simultaneous use without noticeable effect.
Maintenance and Longevity
Instant hot water systems require regular maintenance to perform reliably and achieve full service life.
Annual servicing is recommended for gas instant systems. Service includes cleaning burners, checking ignition components, inspecting heat exchangers, and verifying safety systems. Regular service maintains efficiency and catches problems early.
Water quality affects component life. Hard water causes scale buildup in heat exchangers, reducing efficiency and eventually causing failure. Areas with hard water may need more frequent service or water treatment to protect systems.
Filter cleaning keeps water flowing freely. Inlet filters catch debris that could damage internal components. Regular cleaning prevents flow restriction that affects performance.
Flue inspection ensures safe exhaust. Blocked or damaged flues create safety hazards. Annual inspection verifies flue integrity and clearance from combustibles.
Error codes indicate problems needing attention. Modern systems display error codes when faults occur. Understanding common codes helps identify whether professional service is needed or simple fixes apply.
Expected lifespan for quality gas instant systems is 15-20 years with proper maintenance. Electric point-of-use units may last 10-15 years. Component failures can occur; repair costs vary with what fails and whether parts remain available.
Making the Right Choice
Deciding whether instant hot water suits your situation involves considering several factors.
Usage patterns affect suitability. Households with predictable, moderate hot water use suit instant systems well. Very high simultaneous demand may exceed capacity without very large units.
Space constraints favor instant systems. If you lack room for a storage tank, instant systems' compact wall-mounted design solves the problem. Small units for a kitchen or bathroom in renovated spaces work well.
Gas availability determines options. Properties without gas can only use electric instant systems, which limits capacity. Gas properties have more flexibility in system selection.
Budget considerations include both upfront and ongoing costs. Instant systems typically cost more to install than basic electric storage but less than premium storage options. Running costs are usually lower.
Long-term plans matter. If you plan to add bathrooms or increase household size, current capacity may become inadequate. Consider future needs when sizing systems.
Environmental priorities may influence choice. Eliminating standby losses reduces energy waste. However, heat pumps offer even better efficiency for those prioritizing environmental impact.
Common Questions and Concerns
People considering instant hot water often have specific questions about how these systems work in practice.
Water temperature control is precise in quality systems. Set your preferred temperature and the system delivers it consistently. Better units have digital controls allowing precise adjustment.
Multiple outlet use works fine within system capacity. A properly sized system handles typical combinations like shower plus kitchen tap. Unusual simultaneous demand may exceed capacity on smaller units.
Power outages don't create hot water problems because there's nothing stored to lose temperature. When power returns, hot water is available immediately.
Relocation is possible if you move house. Wall-mounted units can be uninstalled and reinstalled, though new gas or electrical connections may be needed at the new location.
Installation Process
Understanding the installation process helps set expectations and prepare for the work.
Site assessment determines the best location and confirms requirements. The plumber checks gas supply capacity, electrical availability, water pressure, and potential mounting locations before quoting definitively.
Old system removal happens first if replacing existing equipment. For storage systems, draining the tank and disconnecting services takes time. Disposal of old equipment is typically included.
New unit mounting requires solid wall attachment. The unit needs secure fixing capable of supporting its weight. Indoor units need appropriate flue routing; outdoor units need weather protection consideration.
Connections link gas, water, and electrical services. Gas connections must comply with gas fitting regulations. Electrical work must meet electrical safety requirements. Both may require additional tradesperson involvement.