7 Different Types of Gas Hot Water Systems

A gas hot water system is a water heater that uses natural gas or LPG (Liquid Petroleum Gas) to heat water for residential and commercial hot water needs.

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The 7 Different Types of Gas Hot Water Systems

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1. Storage Tank Gas Water Heaters: Storage tank gas water heaters have an insulated tank that stores hot water ready for use. The system uses a gas burner located at the bottom of the tank to heat the water. When hot water is used, cold water enters the bottom of the tank and is heated. Available in sizes from 90L to 170L for domestic use. Good for households with moderate hot water demands. Provides mains pressure hot water. Takes up more space than instantaneous systems. Some heat loss occurs through the tank walls.
2. Tankless Gas Water Heaters: Tankless gas water heaters, also known as instantaneous gas hot water systems, heat water only when needed without storing it. When you turn on a hot water tap, cold water flows through a heat exchanger that is warmed by a gas burner. Compact wall-mounted design saves space. No standby heat loss as water is only heated when needed. Endless supply of hot water (never runs out). More energy-efficient than storage systems. May struggle with multiple hot water demands simultaneously.
3. Condensing Gas Water Heaters: Condensing gas hot water systems are a highly efficient type that captures heat from exhaust gases that would otherwise be wasted. This recovered heat is used to pre-heat the incoming cold water before it reaches the main heat exchanger. Higher energy efficiency ratings (often 5+ stars). Lower operating costs than standard gas systems. Reduced environmental impact. Higher initial purchase cost but better long-term savings. Available in both storage and tankless models.
4. Non-Condensing Gas Water Heaters: Non-condensing gas water heaters are the traditional type of gas hot water system. They vent exhaust gases directly outside without capturing the heat contained in these gases. More affordable upfront cost. Simpler design with fewer components. Easier installation process. Lower energy efficiency compared to condensing models. Higher operating costs over time.
5. Hybrid Gas Water Heaters: Hybrid gas hot water systems combine gas heating with another technology, typically a heat pump or solar assistance, to improve efficiency. These systems use gas as the primary or backup heating source. Reduced gas consumption. Lower running costs than standard gas systems. Greater environmental benefits. More complex installation. Higher initial investment with longer payback period.
6. Continuous Flow Hot Water Systems: Continuous flow gas hot water systems are an advanced form of tankless water heater with higher flow rates and more consistent temperature control. They can handle multiple hot water demands simultaneously. Available with flow rates from 12L to 32L per minute. Can serve multiple bathrooms at once. Electronic temperature control. Consistent hot water temperature. Requires both gas and electrical connections.
7. Instantaneous Hot Water Heaters: Instantaneous hot water heaters are smaller capacity tankless systems ideal for point-of-use applications or smaller households. They provide hot water on demand but are limited in their flow rate compared to continuous flow systems. Flow rates typically between 10L to 16L per minute. Perfect for supplying one or two outlets. Highly energy efficient with 4-5 star ratings. Compact design for easy installation. Available with pilot light or electronic ignition.

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1. Storage Tank Gas Water Heaters

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Storage tank gas water heaters are traditional systems that heat and store water in an insulated tank, keeping it ready for use at any time. A gas burner located at the bottom of the tank heats the water to a preset temperature. When hot water is used, cold water enters the tank through a dip tube at the bottom while hot water is drawn from the top.

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These systems work on a simple principle: the thermostat monitors water temperature and activates the gas burner when it falls below the set level. The burner heats the water, and the process continues to maintain the desired temperature. A flue in the center of the tank vents combustion gases outside, while simultaneously transferring heat to the surrounding water.

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The average lifespan of a storage tank gas water heater is 10-15 years with proper maintenance compared to tankless systems that can last 20+ years. Regular maintenance, including checking the pressure relief valve and flushing the tank annually, can extend its lifespan.

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For energy efficiency, gas storage water heaters typically have a Uniform Energy Factor (UEF) rating between 0.60-0.70, meaning they convert 60-70% of the gas energy into heat for water with higher UEF values indicating better efficiency. Modern high-efficiency models can achieve ratings up to 0.80, with ENERGY STAR certified models offering better performance.

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The average cost of installing a standard storage tank gas water heater in Australia ranges from $1,200 to $2,000, including the unit and professional installation. High-efficiency models can cost $300-$500 more. Annual maintenance costs are relatively low, typically $100-$150 for professional servicing, which should include flushing the tank and checking valves and connections.

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Pros:

• Lower upfront cost compared to tankless systems
• Simpler installation, especially as a replacement for an existing tank system
• Can supply multiple fixtures simultaneously without pressure drops
• Less complicated to repair with more available service technicians

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Cons:

• Higher energy consumption due to standby heat loss
• Limited hot water supply based on tank capacity
• Takes up more space than tankless alternatives
• Gas storage systems are particularly inefficient in cold climates due to high heat loss at the point where the gas flame heats the tank 
• Shorter lifespan than tankless models

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2. Tankless Gas Water Heaters

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Tankless gas water heaters, also known as instantaneous or continuous flow systems, heat water directly as it flows through the unit without storing it. When a hot water tap is turned on, cold water travels through a pipe into the unit where a gas burner heats it instantly via a heat exchanger.

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These systems operate on demand—they detect water flow when a hot water tap opens, which triggers the gas burner to ignite. The water circulates through the heat exchanger, where it's rapidly heated to the set temperature. Once the tap is closed, the unit shuts down, conserving energy when hot water isn't needed.

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The average lifespan of a tankless gas water heater is significantly longer than storage models, typically 20+ years with easily replaceable parts that may extend their life by many more years. Regular maintenance, including descaling to remove mineral buildup, is essential to maintain efficiency and longevity.

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For energy efficiency, tankless gas water heaters are considerably more efficient than storage models, with UEF ratings typically between 0.80-0.95. According to the EPA, tankless water heaters can use up to 34% less energy than storage tank water heaters for households using 41 gallons or less of hot water daily.

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The average cost of installing a tankless gas water heater in Australia ranges from $1,800 to $3,000, including the unit and professional installation. Installation costs can be higher if gas line upgrades or additional venting is required. Annual maintenance costs average $150-$200, primarily for descaling and checking gas connections.

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Pros:

• Energy savings of 24-34% for homes that use 41 gallons or less of hot water daily 
• Endless supply of hot water without the limitations of a tank
• Compact design that saves valuable space
• Longer lifespan with replaceable parts
• More precise temperature control

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Cons:

• Higher upfront purchase and installation costs
• May require upgrading gas lines or venting systems
• May not supply enough hot water for simultaneous, multiple uses in large households 
• Requires both gas and electrical connections
• Slightly longer wait time for hot water to reach fixtures

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3. Condensing Gas Water Heaters

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Condensing gas water heaters are advanced heating systems that maximize energy efficiency by capturing and utilizing heat from exhaust gases that would otherwise be wasted. These systems use a secondary heat exchanger to extract additional thermal energy from combustion gases, allowing them to achieve significantly higher efficiency ratings than conventional models.

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These systems work through a dual heat exchange process. The primary heat exchanger functions similarly to traditional gas water heaters, transferring heat from the burner flame directly to the water. What sets condensing models apart is the secondary heat exchanger, which captures heat from hot exhaust gases before they exit through the flue. As these gases cool below 55°C (131°F), water vapor in the exhaust condenses, releasing latent heat that is then transferred to incoming cold water, preheating it before it reaches the primary heat exchanger.

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The average lifespan of condensing gas water heaters is typically 15-20 years when properly maintained with annual professional servicing. While their more complex design with additional components might suggest a shorter lifespan, modern models use corrosion-resistant materials like stainless steel alloys to counteract the effects of acidic condensate, helping them last as long as or even longer than non-condensing models.

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For energy efficiency, condensing gas water heaters significantly outperform non-condensing models, achieving Uniform Energy Factor (UEF) ratings of up to 0.96, meaning they convert up to 96% of the fuel they use into heat for water. The typical efficiency rating for these systems is around 90-98%, compared to the 80-85% efficiency of non-condensing models. This translates to approximately 10-15% greater fuel efficiency.

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The average cost of installing a condensing gas water heater in Australia ranges from $2,000 to $3,500, including the unit and professional installation. While this is higher than non-condensing models, government rebates and incentives for high-efficiency systems may offset some of this cost. Annual maintenance costs average $150-$250, as these systems require regular professional servicing to ensure the condensate drain lines remain clear and heat exchangers function properly.

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Pros:

• Superior energy efficiency with UEF ratings up to 0.96
• Lower operating costs that offset the higher initial investment over time
• Reduced environmental impact with lower greenhouse gas emissions
• Can use PVC or polypropylene venting materials as the exhaust is cooler, reducing installation costs
• Higher flow rates available for larger households

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Cons:

• Higher upfront purchase and installation costs
• More complex design requiring professional installation
• Requires a drain for condensate disposal
• More frequent maintenance needed due to additional components
• Takes up slightly more space due to the secondary heat exchanger

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4. Non-Condensing Gas Water Heaters

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Non-condensing gas water heaters are traditional gas-powered systems that use a single heat exchanger to transfer heat from the burner flame to the water without recovering heat from exhaust gases. These systems represent the conventional approach to gas water heating that has been used for decades.

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These systems operate with a straightforward design: cold water enters the heat exchanger where it's warmed by the gas burner's flame. The resulting hot exhaust gases, which can reach temperatures as high as 300-400°F (149-204°C), are vented directly outside through a flue system. Unlike condensing models, these systems do not attempt to capture the significant heat energy contained in these gases, which accounts for their lower efficiency.

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The average lifespan of non-condensing gas water heaters is typically 15-20 years, which is similar to condensing models, when properly maintained. Their simpler design with fewer components can mean fewer failure points, but this advantage is somewhat offset by the hotter operating temperatures that may cause more wear on parts over time.

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For energy efficiency, non-condensing gas water heaters typically achieve Uniform Energy Factor (UEF) ratings of around 0.80, meaning they convert about 80% of the fuel they use into heat for water. This efficiency level, while lower than condensing models, still represents a significant improvement over older conventional water heaters and some electric models.

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The average cost of installing a non-condensing gas water heater in Australia ranges from $1,400 to $2,200, including the unit and professional installation. While the upfront cost is lower, the venting system requires more expensive materials like stainless steel due to the higher temperature of exhaust gases. Annual maintenance costs are typically $100-$150, which is lower than condensing models due to the simpler design.

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Pros:

• Lower upfront purchase and installation costs
• Simpler design with fewer components that may require repair
• Slightly smaller size and lighter weight due to single heat exchanger
• Proven reliability with decades of real-world performance
• Less complex maintenance requirements

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Cons:

• Lower energy efficiency with typical UEF ratings around 0.80
• Higher operating costs over the system's lifetime
• Lower energy efficiency with ratings around 80%, leading to higher energy consumption
• Requires more expensive metal venting materials due to hotter exhaust
• Greater environmental impact with higher carbon emissions
• May not qualify for energy efficiency rebates and incentives

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5. Hybrid Gas Water Heaters

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Hybrid gas water heaters are innovative systems that combine gas heating technology with another heating method, typically a heat pump, to maximize energy efficiency. These systems use gas as either the primary heating source or as a backup to supplement the other technology, offering the best of both worlds in terms of efficiency and performance.

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These systems work by utilizing a heat pump as the primary heating method, which extracts heat from the surrounding air and transfers it to the water. When hot water demand increases beyond what the heat pump can efficiently provide, or when ambient temperatures are too low for optimal heat pump operation, the gas burner activates to supplement or replace the heat pump's operation. This dual-heating approach allows the system to optimize energy use based on demand and external conditions.

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The average lifespan of hybrid gas water heaters typically ranges from 13 to 15 years, which is longer than conventional electric water heaters that usually last 8 to 12 years. With proper maintenance, including annual professional servicing and regular system checks, these systems can often reach the upper end of their expected lifespan, providing reliable service for many years.

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For energy efficiency, hybrid gas water heaters are among the most efficient water heating options available, with Uniform Energy Factor (UEF) ratings that can reach up to 0.90 or higher. These systems can reduce energy consumption by up to 60-70% compared to standard electric water heaters, resulting in significant savings on energy bills over time. Many models achieve efficiency ratings above 90% when operating in their optimal mode.

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The average cost of installing a hybrid gas water heater in Australia ranges from $2,500 to $4,000, including the unit and professional installation. While this represents a higher initial investment compared to conventional systems, government rebates for energy-efficient appliances may help offset some of this cost. Annual maintenance costs average $150-$300, reflecting the more complex technology that requires professional servicing to ensure optimal performance.

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Pros:

• Superior energy efficiency compared to conventional gas or electric systems
• Lower operating costs that can save hundreds of dollars annually
• Reduced environmental impact with lower greenhouse gas emissions
• Versatile operation that adjusts to demand and environmental conditions
• Eligible for energy efficiency rebates and incentives in many areas

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Cons:

• Higher upfront purchase and installation costs
• More complex system with additional components that may require repair
• Requires adequate space for installation with proper ventilation
• Performance can be affected by ambient air temperature and humidity
• May require both gas and electrical connections for operation

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6. Continuous Flow Hot Water Systems

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Continuous flow hot water systems, also known as instantaneous or tankless water heaters, provide hot water on demand without storing it in a tank. These gas-powered systems heat water instantly as it passes through the unit, delivering a constant supply of hot water whenever needed.

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These systems operate through a relatively simple process: when a hot water tap is opened, a flow sensor detects the water movement and signals the system to activate. Cold water passes through a heat exchanger, where a gas burner rapidly heats it to the preset temperature. Once the water reaches the desired temperature, it's delivered directly to the tap. When the hot water tap is closed, the system automatically shuts down, conserving energy when hot water isn't needed.

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The average lifespan of continuous flow gas hot water systems typically ranges from 15 to 20 years, which is significantly longer than conventional storage tank systems. Some premium models with proper maintenance can last 20+ years, making them one of the most durable water heating options available. Their extended lifespan is largely due to the absence of a storage tank, which eliminates issues like tank corrosion that commonly lead to system failure.

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For energy efficiency, continuous flow gas systems typically achieve Uniform Energy Factor (UEF) ratings between 0.80 and 0.95, with premium models reaching up to 6+ star energy ratings. These systems are approximately 22-34% more energy efficient than traditional storage tank water heaters because they eliminate standby heat loss associated with keeping a tank of water hot 24/7.

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The average cost of installing a continuous flow gas hot water system in Australia ranges from $1,000 to $1,500 for the unit itself, with total installation costs typically between $1,500 and $2,500 depending on complexity. Running costs are generally lower than storage systems, ranging from $150 to $500 per year depending on household size and hot water usage. Annual maintenance costs are relatively low, typically $100-$150 for professional servicing, which should include checking gas connections and cleaning heat exchangers.

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Pros:

• Endless supply of hot water without the limitations of a tank
• More energy-efficient than storage systems due to elimination of standby heat loss
• Compact wall-mounted design that saves valuable space
• Longer lifespan than conventional storage systems
• Lower running costs compared to electric or storage gas systems
• Precise temperature control for consistent hot water delivery

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Cons:

• Higher upfront cost compared to basic storage systems
• May require upgrading gas lines for adequate gas flow
• Potential "cold water sandwich" effect between uses
• Output can be limited during periods of high simultaneous demand
• Slightly longer wait time for hot water to reach distant fixtures
• Requires both gas and electrical connections for operation

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7. Instantaneous Hot Water Heaters

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Instantaneous hot water heaters are compact, point-of-use systems that heat water on demand without using a storage tank. These systems are typically smaller than continuous flow models with lower flow rates, making them ideal for single-point applications or households with limited hot water needs.

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These systems operate using a relatively simple mechanism: when a hot water tap is opened, cold water flows through the unit, triggering a flow sensor. This activates either a gas burner or heating element that rapidly warms the water as it passes through a heat exchanger. Unlike continuous flow systems which are designed for whole-house applications, instantaneous units are typically designed for point-of-use installation closer to where hot water is needed, such as under a sink or near a shower.

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The average lifespan of gas instantaneous hot water heaters is approximately 15-20 years with proper maintenance. These systems often last longer than storage tank models because they don't suffer from tank corrosion issues and have fewer moving parts that can fail. Models with high-quality heat exchangers made from stainless steel or copper typically offer the longest service life.

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For energy efficiency, instantaneous hot water heaters generally achieve 4-5 star energy ratings, with a typical Uniform Energy Factor (UEF) ranging from 0.80 to 0.85. These systems are more efficient than storage tank models because they eliminate standby heat loss, but their efficiency is typically slightly lower than larger continuous flow systems. The overall energy savings can range from 20-30% compared to conventional storage tank systems for small household applications.

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The average cost of installing an instantaneous gas hot water system in Australia ranges from $800 to $1,200 for the unit itself, with total installation costs between $1,200 and $1,800. These systems are generally less expensive than larger continuous flow models but may have higher per-liter hot water costs due to their smaller size. Annual maintenance costs are minimal, typically around $80-$120 for professional servicing, primarily to check gas connections and clean the heat exchanger of any mineral buildup.

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Pros:

• Compact size ideal for space-constrained installations
• Lower upfront cost compared to larger continuous flow systems
• Energy-efficient operation with no standby heat loss
• Point-of-use installation reduces water wastage waiting for hot water
• Available with either pilot light or electronic ignition options
• Simple installation process compared to whole-house systems

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Cons:

• Limited flow rates typically between 10-16 liters per minute
• Can only service one or two outlets effectively at a time
• Not suitable for households with high simultaneous hot water demands
• May struggle with temperature stability during fluctuating water pressure
• Typically requires annual maintenance to prevent scaling in heat exchanger
• Shorter warranty periods compared to premium continuous flow models

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How to choose the best Gas hot water system type

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When selecting a gas hot water system, the decision should be based on your specific needs, considering both residential and commercial applications, as well as numerous practical factors.

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Residential applications typically have intermittent hot water demands with peak usage in mornings and evenings. For most households, a continuous flow system with a capacity of 20-26 liters per minute provides sufficient hot water for multiple simultaneous uses. These systems offer an excellent balance of efficiency and performance for daily family life while being more environmentally friendly with lower emissions compared to standard electric heaters.

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Commercial applications require systems that can handle sustained high-volume hot water demands. Commercial-grade continuous flow systems offer higher flow rates and can be installed in banks (multiple units working together) to meet extensive hot water needs. For restaurants, hotels, or gyms, condensing continuous flow systems provide the best efficiency and can handle the heavy daily usage with designs specifically meeting high demand requirements for apartments, office buildings, and schools.

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• Small households (1-2 people): An instantaneous or small continuous flow system (16-20L/min) is typically sufficient. These systems provide adequate hot water for a single bathroom home while minimizing energy costs. Storage tank systems are generally oversized and less economical for small households.
• Medium households (3-4 people): A medium-capacity continuous flow system (20-26L/min) or a condensing model offers the best balance of performance and efficiency. These systems can handle multiple simultaneous hot water demands such as a shower running while the dishwasher is operating with capacities around 26L per minute being suitable for medium to large households.
• Large households (5+ people): For homes with high hot water demands, either a high-capacity continuous flow system (26-32L/min) or multiple continuous flow units working together are recommended. Alternatively, a larger storage tank system (170L+) might be necessary if multiple bathrooms are frequently used simultaneously.

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Installation costs vary significantly based on the system type:

• Storage tank systems: $1,400-$2,200 installed, with simpler installation requirements if replacing an existing tank
• Continuous flow systems: $1,500-$2,500 installed, potentially higher if gas line upgrades are needed
• Condensing systems: $2,000-$3,500 installed, offering the highest efficiency but at a premium price
• Instantaneous systems: $1,200-$1,800 installed, economical for point-of-use applications

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Space requirements should factor heavily in your decision:

• Continuous flow and instantaneous systems are wall-mounted and take minimal space, making them ideal for apartments or homes with limited installation areas
• Storage tank systems require significant floor space and adequate clearance for maintenance
• Condensing systems are slightly larger than standard continuous flow models due to the secondary heat exchanger

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Lifespan and durability vary by system type:

• Storage tank systems typically last 10-15 years
• Continuous flow and condensing systems generally last 15-20 years
• Instantaneous systems typically last 15-20 years
• Higher-quality stainless steel heat exchangers significantly extend system lifespan compared to copper heat exchangers

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For the best long-term investment, continuous flow models can last more than 20 years, which is approximately twice as long as traditional storage tank systems. This extended lifespan, coupled with their energy efficiency and space-saving design, makes them the preferred choice for most modern Australian homes despite the higher initial investment.

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By carefully weighing these factors against your specific needs, budget constraints, and installation limitations, you can select the gas hot water system that will provide the most effective and economical hot water solution for your home or business.

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What are the hot water system types?

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Hot water systems can be categorized based on their energy source and how they function. Here's a breakdown of the main types of hot water sytems:

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Based on energy source:

• Gas: Uses natural gas or LPG to heat water
• Electric: Uses electricity to power heating elements
• Solar: Harnesses solar energy through roof-mounted collectors
• Heat Pump: Uses electricity to extract heat from surrounding air

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Based on function:

• Storage/Tank Systems: Heat and store water in an insulated tank
• Continuous Flow/Instantaneous Systems: Heat water on demand without storage
• Heat Exchange Systems: Transfer heat from one medium to another
• Combination Systems: Hybrid systems that use multiple energy sources or functions

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The combination of energy source and function creates various hot water system options. For example, you can have a gas storage tank system, an electric continuous flow system, a solar storage system with gas boosting, or a heat pump storage system.

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What is the cheapest gas hot water system type?

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Storage tank gas water heaters are typically the cheapest gas hot water system option in terms of upfront cost. These systems usually range from $800-$1,200 for the unit itself, with total installation costs between $1,200-$1,800 for standard installations.

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They're more affordable for several reasons:

• Simpler technology: Storage tanks use basic heating principles without complex electronics or multiple heat exchangers
• Established manufacturing processes: These systems have been produced for decades, lowering production costs
• Straightforward installation: Installation is typically less complex than continuous flow systems, requiring fewer modifications to existing plumbing and gas lines
• Lower material costs: They don't require the specialized components found in condensing or continuous flow systems

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However, it's important to note that while storage tank systems have the lowest initial cost, they may end up being more expensive in the long run due to:

• Higher energy consumption due to standby heat loss
• Shorter average lifespan of 10-15 years (versus 15-20+ for continuous flow)
• Limited hot water supply that may require oversizing for larger households
• Higher ongoing maintenance costs over the system's lifetime

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For those on a tight budget, a storage tank gas system offers the most affordable entry point into gas hot water, but those looking for better long-term value might consider the higher initial investment of a continuous flow or condensing system.

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What is the most expensive gas hot water system type?

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Condensing gas hot water systems with solar boosting are typically the most expensive gas hot water system type. These premium systems combine advanced condensing technology with solar energy capture, resulting in prices ranging from $3,500 to $5,000+ for complete installation.

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Condensing systems alone (without solar components) are already at the high end of gas water heaters, generally costing $2,000-$3,500 installed. The addition of solar collectors and associated components further increases both equipment and installation costs. These hybrid systems are expensive due to their complex dual heat exchange design, high-grade materials like stainless steel heat exchangers, sophisticated electronic controls, and the specialized installation expertise required.

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While these systems represent the highest upfront investment, they offer superior energy efficiency and the lowest ongoing operational costs among gas systems, potentially offsetting the initial expense over their extended 15-20+ year lifespan.

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What Are the Energy Efficiency Ratings for different gas Hot Water Systems type?

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In Australia, gas hot water systems are rated using a star rating system and Uniform Energy Factor (UEF) measurements. The UEF indicates what percentage of energy input is effectively converted to hot water, with higher numbers representing better efficiency.

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Energy efficiency ratings by system type:

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Storage Tank Gas Water Heaters

• Star Rating: Typically 4-5.3 stars
• UEF/Efficiency: 0.60-0.70 (60-70% efficient)
• High-efficiency models can reach up to 0.80 UEF
• Standby heat loss through tank walls reduces overall efficiency
• Annual gas consumption for standard models: 20-25 GJ/year for average household

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Non-Condensing Continuous Flow Gas Water Heaters

• Star Rating: 5-6 stars
• UEF/Efficiency: 0.80-0.85 (80-85% efficient)
• No standby losses as water is only heated when needed
• Higher instantaneous gas consumption but lower overall usage
• Annual gas consumption for standard models: 15-20 GJ/year for average household

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Condensing Continuous Flow Gas Water Heaters

• Star Rating: 6-7 stars
• UEF/Efficiency: 0.90-0.98 (90-98% efficient)
• Secondary heat exchanger captures waste heat from exhaust gases
• Most efficient gas water heating technology available
• Annual gas consumption for standard models: 12-17 GJ/year for average household

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Instantaneous Point-of-Use Gas Water Heaters

• Star Rating: 4-5 stars
• UEF/Efficiency: 0.80-0.85 (80-85% efficient)
• Smaller size limits maximum efficiency despite on-demand operation
• Best efficiency achieved with mechanical ignition rather than pilot light
• Annual gas consumption varies widely based on point-of-use application

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Hybrid Gas-Solar Hot Water Systems

• Star Rating: Can reach 7+ stars with optimal solar contribution
• UEF/Efficiency: Variable based on solar contribution, but gas component typically 0.80-0.95 efficient
• Solar component reduces gas consumption by 50-75% depending on climate
• Gas booster activates only when solar heating is insufficient
• Annual gas consumption highly variable by location: 5-12 GJ/year for average household

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These efficiency ratings help consumers compare different hot water system types and make informed decisions based on both upfront costs and long-term operational expenses. The energy rating label on gas hot water systems displays both the star rating and estimated annual energy consumption, allowing for direct comparison between models.

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