Expert Advice on Hot Water Systems

If you’re building a new home or are considering changing or upgrading the hot water system in your home, there are several options to choose from. We’ll look at a few options here that the team at Sumich Plumbing & Drainage can help you with, and will help you sort through a few pros and cons of each.

Factors to consider first before looking at different hot water systems

There are several factors that need to be considered before choosing the hot water cylinder system that is right for you:

  • How much hot water your household uses
  • How much you’re willing to spend upfront for installations or upgrades
  • The size of your house and storage space
  • Whether you have access to a gas supply
  • How much you’re willing to spend on running costs

Should you heat your water with gas or electricity?

The two most common fuel sources for heating water in New Zealand are gas and electricity. Which one you decide to use depends on what hot water system you prefer and whether or not you have access to gas.

There are other options, such as solar power or authorised wood burners, but for ease and simplicity, we’ll focus on the most common hot water systems here.

If you decide to use a gas-powered system, remember that only authorised gasfitters are allowed to install, maintain, repair or replace gas appliances in New Zealand. The team at Sumich Plumbing & Drainage are certified gas fitters and registered members of the New Zealand Plumbers, Drainlayers & Gasfitters Association and can help with any of these systems.

Electric Hot Water Cylinder

A hot water cylinder holds a set amount of water that is heated to a pre-set, desired temperature. (The system needs to be set up correctly to ensure the water temperature is kept at 60°C to prevent the growth of legionella bacteria.)

Electric hot water cylinders use an electric element inside the tank to heat the water to a temperature set by a thermostat. The immersion element looks like a metal loop or coil, and acts in a similar way to the electric element inside a kettle to heat the water.

CONS: It will not work during a power outage. They can be more expensive to run than other systems. If you select a cylinder size that isn’t large enough for your household’s hot water needs, you may find that you run out of hot water often.

Gas Hot Water Cylinder

Similar to an electric hot water cylinder, a gas hot water cylinder holds a set amount of water that is heated to a pre-set, desired temperature. The heating of the water, however, is not done by an electric element. The heating of the cylinder is done by natural (mains) gas or bottled (LPG) gas.

Cold water enters the tank at the bottom of the cylinder through a cold water supply tube; the dense cold water at the bottom of the cylinder is then heated by a gas burner located beneath the sealed tank. As the water heats up, it rises to the top of the cylinder. A hot water discharge pipe draws off hot water when needed.

CONS: If you select a cylinder size that isn’t large enough for your household’s hot water needs, you may find that you run out of hot water often. Running costs can be higher than other systems as you need to pay for your gas supply.

Instantaneous / Continuous Flow Hot Water

A continuous flow hot water system works by pushing cold water through piping and applying heat directly to these pipes to heat the water. You may also hear it referred to as instantaneous hot water because it heats water on demand, as you need it. Your plumber may refer to this system as a califont – it’s all the same thing.

The system relies on gas to heat the water, and it can run on both LPG and natural gas. Because you’re not heating water and then storing it in a tank for later use, a gas continuous flow system is more efficient than a hot water cylinder.

PROS: The biggest advantage to using this system is that it provides unlimited hot water. It also includes energy and cost savings compared to traditional hot water cylinders as you’re paying to heat water only as you use it, not to store it. They are also an excellent option for homes with small spaces, as the unit does not have a tank to store water and can be mounted outside. Gas continuous flow systems have reduced gas emissions compared to other gas systems.

CONS: It will not work during a power outage as most systems require an electrical supply. As with gas hot water cylinders, gas continuous flow systems also contribute to climate change by producing greenhouse gases.

Heat Pump Hot Water (HPHW) System

A heat pump hot water heater system uses technology that is similar to a heat pump used to heat rooms. It uses electrical energy and a refrigerant to extract energy from outdoor air to heat the water. The heated water is then stored in an insulated hot water tank.

You can either have a system comprised of two separate units – the heat pump and the hot water cylinder – and these can sit beside each other or one inside and one outside. This might depend on whether you have room in your home for a hot water cylinder or prefer to have it outside.

PROS: They can be more energy efficient than other conventional hot water cylinders. They’re relatively inexpensive to run. They suit a household with moderate to high hot water needs. They can be retro-fitted to work with some models of conventional hot water cylinders. Some systems can also be used to help with central heating.

CONS: They are a bit more expensive upfront to install. They are not as efficient in colder parts of the country. 

Getting the best advice on the hot water system that’s right for you

All of our plumbers at Sumich have extensive knowledge of the different water heating systems available. We’ll ensure you have a system that is most appropriate for your household and your water usage. Get in touch for a free quote* excluding roofing on installing or replacing a hot water system, or upgrading from Low Pressure to Mains Pressure hot water.


There are a number of plumbing and drainage companies in Auckland, so why choose Sumich?

Founded by owner-operator Chris Sumich in 1991, Sumich Plumbing & Drainage has one of the most experienced teams operating in Auckland. Our team has a combined experience of over 100 years and we’ve seen a comprehensive range of scenarios and solutions over the years. Clients trust us to give honest, transparent advice and service.

As registered members of the New Zealand Plumbers, Drainlayers & Gasfitters Association, we are professional, licensed Auckland plumbers for all of your plumbing, drain laying, gas fitting and heating needs. Give us a call to see how we can help.