Hot Water Systems: The Complete Guide

Having the right hot water storage system for your home is just like having the right tool for a job.

Climate, household demand, space, environmental concerns. They’re all crucial factors that can help you decide what system to pick. Plus, putting thought into it now means you won’t be pressed into a stressful decision at 10pm on a Sunday night.

Altogether, heating water can make up close to 30 per cent of your household’s energy use.

Choosing the right hot water system for you

What’s right for you? That’s a question we can’t answer! Instead, we’ll provide plenty of recommendations and information, but the final decision is always yours.

Before looking at the gas vs solar vs electric debate, let’s start with the basics.

What you need to consider

Each hot water unit caters to certain needs. Large storage tanks can supply huge amounts of water for a big household. The yearly expenses are quite high, though. Conversely, a solar hot water system will save money and is environmentally friendly, but may not meet high demand on its own.

Some of the most important aspects for you to consider are:

  • How many people live in your house?
  • Are there peak times where you all have to use hot water?
  • The size of the house and the number of bathrooms
  • Initial costs and long term expenditure
  • How hot do you want the water?
  • Temperature control ability
  • Energy efficiency and environmental impact
  • Energy star rating
  • Space available for installation

Certain factors will be more important to you than others. Is it cutting down on electricity bills, creating fewer greenhouse gasses, or just making sure everyone gets a warm shower in the morning?

Instantaneous or storage tank

Breaking news: a storage tank hot water system isn’t always the best option. We certainly don’t want to disregard it, but in many cases, the long term benefits don’t match up to the alternatives available now.

Why? Let’s compare.

Instantaneous hot water system

An instantaneous, or continuous flow hot water unit only heats water as you need it. How exactly does it work? Well your water pipe runs through a wall mounted unit and as you turn the hot water tap on, a heat exchanger heats the water.

The majority of instantaneous systems run on gas, which equals strong savings.

Storage tank hot water system

Size is the strongest selling point for a storage tank. With units ranging up to the 400l in capacity, there is a huge offering for busy families and households.

Hot water will always be on tap. However, that same convenience means water is heated all day and night, while you’re working or sleeping. You wouldn’t want a kettle to be boiling non stop just for a cuppa after work, so the wasted energy is a bit of a letdown.

On the plus side, most of the costs are associated with electric tanks and savings are available with gas and solar.

Gas, electric or solar hot water systems

What’s the best fuel source for your hot water? Knowing that we’re all stung when the electricity bill comes in, an efficient fuel source can relieve some of the pain. Here’s the good and bad.


For a lot of us, electricity is the only option. Upfront costs on an electric hot water system are generally the lowest, and convenience is high. But with yearly running costs adding up it may be time to consider a change.

Even switching from an electric storage tank to an electric instantaneous unit will provide some noticeable cost savings.

It’s also good to note most companies produce energy efficient models which are generations ahead of technology from 15 years ago.

Electric heat pump

This one’s a bit of a bonus category for electric as it straddles the line of renewable energy. A heat pump hot water system draws in warm air, which is converted into heat, warming up the water.

It’s more efficient than a traditional electrical heater, with three times as much energy created.

There are a couple of drawbacks, though. It requires a good, constant supply of warm air, and can be pretty noisy.


Natural gas costs you a third of what electricity does every year. That’ll negate any high purchase costs within two years of use.

Continuous flow gas heaters are arguably the most efficient model out there. As mentioned earlier, water is heated on demand only, and at a lower cost. The only major considerations are the fact a gas hot water system should be placed outside for safety reasons, and we don’t all have access to gas.


How does a solar hot water system work? On each panel something called an evacuated tube absorbs the sunlight, which is transferred to your tank and heats the water. The larger the tank, the more tubes are needed, e.g. one tube for every 10 litres.

Addressing the elephant in the room, solar does set you back in the first instance. It’s not cheap to buy and installation is specialised. And there is the drawback that when sunlight disappears, you’ll need a gas or electric booster to maximise efficiency all year round, in all conditions.

Despite the negatives, the running costs are incredibly low and you will basically be banking the savings within a few years.

Which hot water system should I buy?

So, what’s the best choice for a hot water system? That’s up to you! Each one has pros and cons for you to consider.

One thing we know at Metropolitan Plumbing is that we are here to help you with any hot water system installation, servicing and repairs. And even though we won’t make the decision for you, we can assess your home and provide the perfect recommendation.

Published: 24 Jun, 2020

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