Over our 15 years in the business, we’ve gotten lots of questions about our heat pump hot water systems. A lot of these answers are too short for a typical article, so we’ve compiled a list here to help you become a hot water expert.

In this article, you’ll learn about tanks with stainless steel or glass lining, tank size, split or integrated systems, noise, and the most important question of all: will you run out of hot water?

Do I need a stainless steel or a glass lined tank for my hot water heat pump?

Glass lined tanks are typically used in places where the water has a high mineral content, or for bore water. If your water isn’t particularly high in mineral content, then you’re better off with a stainless steel tank.

Glass lined tanks require a minimum five years warranty, which has become the industry standard. Steel tanks typically have a warranty of ten years – some premium providers, such as Reclaim Energy, offer a 15 year warranty on their stainless steel tank and an industry leading 10 year warranty on their glass-lined tank.

A stainless steel tank will require less maintenance, as it doesn’t require the sacrificial anode that glass-lined tanks do.

How big should the tank for my hot water system be?

The tank size for a heat pump hot water system largely depends on how many people live in the household. Typically, a tank of around 300-350L is enough to ensure a family of four to five people doesn’t run out of hot water.

Standard thinking is that the average person needs 50L of hot water a day, and that your storage should have 1.5 days capacity. You may have higher needs though, especially if you’re fond of long showers.

Keep in mind, you may one day sell the house to new occupants, so it’s best to determine the size based on how many people the house could fit, rather than how many currently live there. For example, if you have a study that might be used as a bedroom, consider counting that as an extra person – it’ll help with resale value.

When it comes to fitting the tank on your property, you’ll need to have a look at where you think it’ll go, as some manufacturers offer different shapes. Reclaim, for example, offer a tall and squat tank (which requires additional lead-times) – for narrow but tall spaces and wider but shorter spaces.

Will I run out of hot water?

As explained above, if you choose the right sized tank, you shouldn’t expect to be caught out with a cold shower.

However, some factors other than tank size do come into play. Since heat pumps extract heat from the outside air, some systems can struggle to keep up on cold days. CO2 Systems that can operate at -10° are the best investment if you want to be sure that you won’t suddenly run into issues with cold water.

Some systems come equipped with an electric booster that kicks in when the system isn’t able to collect enough heat on its own. This ensures your water stays hot, but it can also lead to much larger electricity bills than otherwise. A system that runs efficiently enough to not require a booster is the best bet to keep your long-term bills low – but obviously, it will be more expensive upfront.

There have been some reliability issues with lower quality systems that mean – even in weather that should be favourable – there’s no hot water. We go into this in more detail in our article about heat pump price ranges.

What’s the difference between a split system and an integrated hot water heat pump?

An integrated unit has the heat pump/compressor mounted on top or attached beside the tank. This means the system is fairly compact and can be simpler to install (other than possibly requiring two people to move, as they’re heavier).

A split system separates the tank and the heat pump. When the system is installed, the two units need to be linked together, which does make the installation more complicated.

However, you get much greater flexibility. You could, for example, keep the heat pump unit outside and keep the tank inside. While the actual install on the day becomes more complicated, it’s also significantly easier to find a spot to install the units – space is less of an issue.

Is noise an issue?

Noise depends on two factors: the model of heat pump and where you place it. Typically, you can expect a pump to run at around 50dB, which is louder than you’d want by your bedroom window when you’re trying to sleep. However, if you’re able to keep the pump somewhere that you don’t expect people to be sleeping, it’s not a huge issue.

Higher-end pumps give you greater flexibility. Some get down to 37dB, which can be installed basically anywhere without the noise being a serious issue. It’ll make it much easier to find a good spot, and helps to keep your options open.

Have more questions?

G Store is committed to educating you on all things hot water. Check out other pages in our learning centre – or, get in touch with our expert team for specialised knowledge on questions specific to your property.

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