Instantaneous Hot Water Systems: How They Work, Costs & Pros/Cons
An instantaneous hot water system, also called a tankless or continuous flow system, heats water on demand instead of storing it in a big tank. That means you don’t have to wait for a big 300-litre tank to refill and reheat; just turn on the tap, and the system starts heating water right away. It’s a space- and energy-saver, and can even save you a bit on your bills. But ‘instant’ can be a little misleading. How fast the hot water actually reaches your tap and whether this type of system is right for your home depends on your house layout, how much water you use, and your plumbing setup. In this guide, we’ll break down how these systems work, how much they cost, their pros and cons, and when they make sense for your home, so you can make an informed decision. TL;DR How Instantaneous Hot Water Systems Work When you turn on a hot tap, water starts moving through the pipe and into the hot water system. A flow sensor inside the unit detects this movement immediately and sends a signal to the electronic control unit (ECU), which acts as the system’s controller. The ECU starts the heating process: At the same time, cold water flows into a copper pipe inside the heat exchanger. The burner or elements heat the exchanger, and that heat transfers through the copper pipe into the moving water. Because the water is constantly flowing, it heats up in seconds and continues heating as long as the tap stays on. Before the water leaves the unit, a thermistor (temperature sensor) measures the water temperature as it reaches the outlet of the unit. The system is mostly set to heat water to around 60°C in Queensland homes to prevent bacterial growth and meets Australian safety standards. If the water isn’t at that set temperature, the electronic control unit (ECU) adjusts the heat instantly by: Once the water reaches that set temperature, it leaves the unit and travels through your pipes. Before it reaches bathroom taps, it passes through a tempering valve, which mixes in cold water to bring it down to a safer 50° to prevent burns. Finally, when you turn the tap off, the water flow stops. The flow sensor detects this, and the ECU shuts down the burner or heating elements, and the system goes back to standby mode. Types of Instantaneous Hot Water Systems Based on Energy Source 1. Natural Gas Systems A natural gas instantaneous system is a tankless unit connected directly to your home’s mains gas supply. These systems can deliver high flow rates because gas burners can produce a large amount of heat very quickly. This high heat output allows the system to heat more water at once, which is why they’re commonly used in family homes with higher hot water demand. In Townsville, homes that already have a gas connection often go with this option because it provides strong, consistent hot water and is typically cheaper to run than electricity. 2. LPG (Liquid Petroleum Gas) Systems An LPG instantaneous system works the same way as a natural gas unit, but instead of being connected to a gas line, it uses gas cylinders stored outside the home. These systems are more expensive to run than natural gas because you not only pay for the gas but also for delivery, bottle refills, and rental of the cylinders. As for performance, there’s no real difference. LPG units still use a gas burner, so they can produce high heat quickly and handle high demand without a noticeable drop in temperature. This makes LPG a practical option for homes that don’t have access to mains gas, which is common in rural or outer parts of North Queensland. 3. Electric Instantaneous Systems Electric instantaneous systems use high-powered heating elements instead of a gas burner to heat water on demand. They’re smaller and more compact because they don’t need parts like a burner, flue, or ventilation, so you can easily have them installed inside cupboards, under sinks, or in tight spaces. But heating water instantly with electricity takes a large amount of energy in a very short time. A standard single-phase power supply can only deliver a limited amount of electricity at once, which is not enough to heat large volumes of water for your entire house while multiple taps are running. To handle higher demand, electric systems require three-phase power. But, most homes don’t have this by default, as single-phase is the standard for residential properties. And if you want to upgrade to three-phase, it often involves changes to the switchboard and supply connection, which is quite expensive. Because of these limits, electric instantaneous systems in Townsville are only used in lower-demand setups, like a single bathroom or a granny flat, where only a small amount of water needs to be heated at a time. Based on Heating Technology 1. Standard (Non-Condensing) Systems A standard instantaneous system is the basic gas model that heats water with a gas burner, and the hot gases created during combustion are vented straight out through a flue. Some of the heat produced in the burner escapes with those exhaust gases, which means not all the energy from the gas goes into heating your water. Because of this, these units are less energy-efficient than newer designs. These systems are popular in many older homes in Australia because they are simple and cheaper to buy upfront. 2. Condensing Systems A condensing instantaneous system is a high-efficiency version of a gas unit. It works like a standard system but with one key improvement: it reuses heat from the exhaust gases. The hot gases from the burner normally leave through the flue. In a condensing system, these gases pass through a second heat exchanger, which transfers much of that leftover heat into the incoming cold water. This means more of the gas energy actually heats your water instead of being wasted. However, these systems cost more upfront, but in Townsville homes

