A hot shower or bath isnât just a luxury; itâs also great for relaxing the muscles and the mind, improving sleep, reducing inflammation and joint pain, and boosting circulation. And itâs not just about bathing â hot water is essential for washing dishes, clothes, cooking, cleaning and more. If youâre constantly running out of hot water, choosing the right size from the start is the best way to avoid those cold, frustrating surprises. Hot water system size is crucial because it determines whether your household will have enough hot water for all your daily needs. When considering system size, think about how much hot water your household uses for activities like showers, laundry, and dishwashing, as this will help you select the right capacity. Ultimately, the size system suits your household best when it matches your unique lifestyle and usage patterns.
Introduction to Hot Water Systems
Hot water systems are a cornerstone of modern living, providing the heated water we rely on for showers, baths, washing clothes, and cleaning dishes. With so many options available, choosing the right hot water system for your home can feel overwhelming. From solar hot water systems and heat pump systems to electric hot water systems, each type offers unique benefits and considerations. The key to finding the right hot water system is to match it to your household size, daily water usage, and energy efficiency goals. By understanding your needs and the features of different hot water systems, you can ensure a reliable supply of hot water while keeping your energy bills in check.
Why Size Matters
When updating your hot water system there are several reasons to get the size right:
- Donât run out of water: If the tank or flow rate is too small, you wonât have enough hot water between heating cycles. A properly sized storage system or storage hot water system is essential to supply hot water during peak demand.
- Be energy & cost efficient: Oversizing means wasted money upfront and on energy bills.
- Make your system last: An underpowered or undersized storage hot water system may struggle to supply hot water efficiently, causing it to work harder, wear out quickly, and require more repairs or earlier replacements.
Convinced that choosing wisely from all those hot water system sizes is critical to keep those steaming showers flowing? Our Sydney plumbers have come up with a step-by-step guide on how to get a head-start on matching the right-sized hot water system to your property, family and needs:
Step 1: Whatâs Your Overall Demand?
Each person in your home uses between 50â75 litres of hot water daily. For a family of four thatâs 200â300 litres per day, so itâs important to have a water heater or hot water heater that matches this demand. Usage varies: some like long, luxurious showers or baths, others quick or even cold showers. Consider the number of bathrooms and the use of appliances like dishwashers and washing machines that draw on your hot water system. Different water heaters have varying capacities to meet household needs. As hot water is used, cold water enters the system to be heated for the next cycle.
Step 2: Try a Hot Water Calculator
Most manufacturers and plumbers have sizing charts or online calculators. These tools help determine the appropriate hot water tank, water tank, or storage tank size by matching your household size, routines and appliances to the right hot water system. Calculators also consider different system types, such as electric storage and electric storage hot water systems.
Step 3: What Flow/Delivery Rate Do You Need?
Besides tank capacity, flow and delivery rates also matter. This is how quickly hot water gets to your taps, especially when multiple outlets are in use. Typical Australian rates:
- Electric hot water systems: 20â25 litres/minute. This includes electric water heaters such as electric storage systems, which have set flow and recovery rates depending on tank size and heating element.
- Gas hot water systems: Up to 40 litres/minute
- Instant hot water systems: Variable (10â32 litres/minute). Continuous flow systems (also known as a continuous flow system) provide hot water on demand, are sized by the number of outlets, and do not use a storage tank.
- Local water pressure can affect flow rates.
Hot Water System Sizing Charts
Here are Australian guidelines for sizing your hot water system. Proper sizing is essential for both storage water heater and storage systems, which are among the most common types used in homes:
| Number of People | Peak Usage | Electric Tank (L) | Gas Tank (L) |
| 5â8 | High | 400 | 340 |
| Low | 250 | 170 | |
| 3â6 | High | 315 | 260 |
| Low | 160 | 160 | |
| 2â4 | High | 160 | 160 |
| Low | 125 | 135 | |
| 1â3 | High | 125 | 135 |
| Low | 80 | 90 |
For gas tank options, note that gas models using natural gas may have different sizing requirements due to their efficiency and heating characteristics.
For instant systems, select based on number of simultaneous outlets (e.g., a 24L unit for three outlets running at once).
Peak Usage and Simultaneous Hot Water Demand
âPeak usageâ refers to times when hot water demand spikes, such as when everyone showers in the morning. Using off peak times and off peak electricity can affect how much hot water needs to be stored, as the system must supply hot water during periods of high demand even if heating only occurs overnight. If you select an off peak tariff, you may need a larger tank to ensure there is enough hot water available throughout the day. If multiple appliances or taps are used at once, choose a system with enough flow rate and/or tank size to prevent cold showers.
Planning for Household Changes
Consider future needs â growing families, guests or renovations can increase hot water demand. When planning ahead, itâs important to choose a storage hot water system or storage hot water systems with a storage tank that is appropriately sized to accommodate potential growth. Size a little larger if you foresee more occupants but donât oversize.
How Appliances Affect Hot Water Sizing
Washing machines, dishwashers and other appliances impact hot water demand, with the washing machine being a key factor in many households. Check appliance specs or estimate usual loads and add this to your daily demand. The number of hot water taps used simultaneously and the desired water temperature also influence the required system size. If appliances run while people are showering your system must handle this peak.
Types of Hot Water Tanks
- Mains Pressure: Delivers strong flow, suitable for most homes.
- Gravity Feed: Older, usually lower pressure, used in multi-storey or remote homes.
- Continuous Flow (Instantaneous): No tank, heats water as needed, sized by simultaneous outlets.
For storage water heaters, an insulated tank is important to reduce heat loss and maintain water temperature, especially in cold weather and cold climates.
Heat pumps and heat pump hot water systems are energy-efficient alternatives that often use an outdoor unit. These systems rely on heat pump technology to extract heat from the air, making them effective even in cold climates and during cold weather. A pump hot water system can help you save energy and reduce running costs.
For solar options, solar water heaters, solar hot water system, and other solar systems use solar powered collectors to heat water. Solar power can be used directly for water heating, or a solar PV system can generate electricity to power electric water heaters. Some solar systems include a gas booster or gas boosters to maintain hot water supply during periods of low sunlight or high demand. Note that gas systems typically use fossil fuel.
Each type has sizing and installation differences.
Energy Efficiency Options
When selecting a hot water system, energy efficiency should be at the top of your list. Solar hot water systems are a popular choice for households with ample roof space and high hot water demand. By harnessing solar panels to heat water, these systems can significantly reduce your reliance on grid electricity and help lower your energy bills. If your roof space is limited, heat pump systems offer another energy-efficient solution. These systems use heat from the surrounding air to heat water, making them ideal for a variety of home layouts. Electric hot water systems, while generally less efficient, can still be cost-effective when paired with off-peak tariffs or solar PV systems. By evaluating your homeâs energy usage patterns and exploring options like solar hot water systems and heat pump systems, you can choose a hot water system that saves energy and money in the long run.
Safety and Hygiene Standards
Australian standards require hot water storage tanks to keep water above 60°C to inhibit Legionella. Tempering valves are critical for preventing scalding especially in homes with children, elderly or healthcare settings.
Energy Tariffs and Tank Sizing
For electric systems, your energy tariff (peak, shoulder, off-peak) impacts capacity needs. This is especially relevant for electric storage water heater, electric storage, and electric storage hot water systems, which are common options affected by tariff selection. Off-peak tariffs mean youâll need a larger tank to store enough hot water for the day, while peak tariffs allow for smaller tanks as youâll be reheating more frequently.
Installation and Maintenance
Proper installation and regular maintenance are essential for getting the most out of your hot water system. A licensed professional can help you select and install the most efficient hot water system for your household, ensuring it meets your specific needs and complies with safety standards. Routine maintenance, such as checking the temperature and pressure relief valve, inspecting the heating element, and monitoring the thermostat, can help prevent common issues like overheating or leaks. By staying on top of maintenance, youâll extend the life of your hot water system, maintain its efficiency, and enjoy a steady supply of hot water whenever you need it.
Upgrading Your Hot Water System
If your current hot water system is struggling to keep up or your energy bills are on the rise, it may be time to consider an upgrade. Investing in a new hot water system can improve energy efficiency, increase your hot water supply, and reduce long-term costs. When upgrading, think about your household size, typical water usage, and the energy efficiency of different systems. Modern options like solar hot water systems, heat pump systems, and high-efficiency electric hot water systems are designed to deliver reliable hot water while minimizing energy consumption. Itâs also important to check that your new system is compatible with your homeâs existing plumbing and electrical setup. By choosing an efficient hot water system that fits your needs, youâll enjoy lower energy bills and a more sustainable home for years to come.
Quick Reference Tables for Sizing
Summary tables or online calculators can help quickly estimate the right system size. Check your existing water bills, tank capacity and actual household usage to refine your choice and avoid guesswork.
Weâll Help You Choose Hot Water System Sizes
However, itâs also important to consult with a hot water system plumber before deciding on the right hot water size, because youâll also need to factor in the hot water system installation, the available energy sources, ongoing maintenance considerations and the best brands and warranties.
And here at Rapid Service Plumbing, weâve installed, repaired and worked on so many different properties and hot water technologies that we can easily recommend the perfect hot water type, size, and model for your home & budget â no worries! For a no-obligation consultation & quote with a $0 call-out fee all across Sydney and beyond, get in touch with Rapid Service Plumbingâs hot water specialists today.
