When shopping around for a hot water heat pump, one thing you might notice is that there seems to be a difference between so-called “split” systems and “all-in-one” systems.
Indeed, there are differences. Some are minor, and would barely factor into a buying decision. However, there are a few things that might influence you one way or the other. Here, we go into all the differences between split heat pumps and all-in-ones, so you have all the information you need to make the informed choice.
The compressor is the main difference
An all-in-one, also called an “integrated” system, combines both the compressor and the tank. They’re combined, usually with the compressor on top of the tank.
If you’re wondering what the compressor is, it’s the unit responsible for heating your water. It works by absorbing heat from the air, compressing that to increase its pressure and temperature, and then passing that heat into the water tank. (We’ve got an in-depth explanation of how heat pumps work here.)
The next question is obvious: why does it matter? While it seems like a trivial difference, it can actually affect quite a few things.
For starters, a split system has a more involved install. Since they’re not already, the compressor and hot water tank have to be connected to each other – naturally, this makes the install more intricate.
The trade-off is that you get extra versatility. It can be difficult to find an appropriate spot for both the compressor and the tank. With a split system, you might place the compressor outside and keep the tank somewhere inside, which makes it easier to find a suitable location. It’s a misconception that an all in one saves space because it’s more compact. These integrated systems need quite a bit of clearance from the wall, whereas a split system’s tank can hug the wall and reduce the system’s profile.
For example, some homeowners end up with a heat pump outside their bedroom window, which can cause an annoying amount of noise. Because the compressor is on top of the unit, up high, the sound travels much further than if it were mounted close to the ground. (Some really good heat pumps, like the Reclaim CO2 or the Sanden Eco Plus, have noise profiles quiet enough that this isn’t an issue, especially because they can be mounted low– but most are fairly loud. Not to mention that these top of the line heat pumps are split systems anyway, for reasons we’ll cover in the next section.)
Splitting gets you more efficiency
You’ll find that the most expensive (and highest efficiency) heat pumps are split systems. Fitting the compressor on the tank requires that it be fairly compact compromising efficiency, whereas split systems don’t have this restriction. They can have a larger, more efficient compressor – that doesn’t just mean saving money by using less electricity, it also means you refill the tank faster, getting more reliable access to hot water.
This means for larger families with high hot water use, a split system is often the best option. The smaller compressors of integrated systems just don’t cut it for large households. The best split systems can reheat a 315L tank in three hours, whereas an integrated system might take many hours more than that. If you end up with an all-in-one model by a bedroom window, you’ll have to put up with that noise for hours and hours.
Additionally, the smaller compressor means that integrated units often struggle to get water to sufficiently high temperatures – the temperatures needed to kill legionella and other bacteria. That doesn’t mean they’re unsafe, because they get around this by using an electric booster to get the rest of the way. What this means, though, is that they have to rely on that much less efficient booster some of the time. It might not be much in that moment, but the difference does stack up over time. Keep in mind, that’s on top of the fact that integrated systems tend to be less efficient.
This also means that split systems, typically, aren’t just more expensive to install – they’re also more expensive to buy. A great split system will be around $5,000, whereas you can find cheap integrated models starting around $2,000. That gets paid off over time by the difference in savings, but it’s more expensive upfront.
The thing to keep in mind is that you’ll want to make sure the compressor is the right size for you, even if it costs more. If you’re regularly running out of hot water and need to get a bigger compressor to refill the tank faster, that upgrade will be more expensive. You can only get the Victorian government’s sizeable Solar Homes rebate once, so make sure you use it on the right system.
Conclusion
An integrated system is cheaper and easier to get installed, but it lacks the flexibility of a split system. It might not be the right option if you have a larger household and need reliable access to a lot of hot water.
At the end of the day, there’s always a compromise made with an integrated system. You can think of it as WERN – Warranty, Efficiency, Recovery Rate, and Noise. With all of these, you’ll get better results with a split system.
Split vs integrated isn’t the only thing to keep in mind when upgrading to a heat pump. The other pages on our Learning Centre go into detail on everything else you need to know.