Sunamp vs hot water cylinder: Which is the better choice?

If you’re replacing an ageing hot water cylinder or planning a more energy-efficient home, you’ve probably come across Sunamp heat batteries. They deliver mains pressure hot water, while taking up a fraction of the space of a traditional cylinder. But how do they compare in the real world?

Is Sunamp really better than a conventional hot water cylinder, or is it simply a different way of storing energy? Here’s everything you need to know.

How does a traditional hot water cylinder work?

A traditional hot water cylinder stores a tank full of heated water, ready for when you need it. The water is typically heated by a gas boiler, immersion heater, or heat pump before sitting inside the cylinder until it’s used.

Although modern cylinders are well insulated, they’re still storing hot water all day and night. Over time, that heat gradually escapes, meaning the cylinder needs reheating to maintain its temperature.

For decades this has been the standard way of providing domestic hot water, and for many homes it still works well.

How is Sunamp different?

A Sunamp doesn’t store hot water at all. Instead, it stores heat inside a special phase change material (PCM). When you turn on a hot tap, cold mains water passes through an internal heat exchanger where it is instantly heated before leaving the unit. As there’s no stored hot water, there are no risks associated with stagnant water, and there’s significantly less standing heat loss compared to traditional cylinders.

The result? Compact, efficient hot water, whenever you need it.

Space saving

One of the biggest advantages of a Sunamp is its size. Traditional cylinders often requite an airing cupboard or dedicated plant room, and in smaller homes, this valuable storage space can feel like a luxury.

Sunamp units are much more compact, and can often be installed under stairs, in utility rooms, garages, or kitchen cupboards where a conventional cylinder simply wouldn’t fit. For homeowners renovating or extending their property, recovering an entire airing cupboard can make a surprising difference.

Energy efficiency

Every hot water cylinder loses heat over time. Even the best insulated models gradually cool down, meaning they’ll need reheating throughout the day.

A Sunamp stores thermal energy rather than hot water, so standing losses are much lower. More of the energy you put into the unit is available when you actually need hot water. If you’re charging your Sunamp using excess solar generation or cheaper overnight electricity rates, this improved efficiency can help reduce your overall energy bills.

Performance

Both a hot water cylinder and a Sunamp can provide plenty of hot water when correctly sized. As a Sunamp heats water instantly as it flows through the unit, you don’t have to worry about maintaining a tank of stored water at a specific temperature. You’ll also get consistently strong mains pressure hot water throughout the property, provided your incoming mains supply is adequate.

Safety

Traditional cylinders store large volumes of hot water, which is why they include safety valves, expansion vessels, and other protective components.

A Sunamp stores thermal energy instead of hot water, meaning it avoids many of the risks associated with storing large quantities of pressurised hot water. For many homeowners, this provides extra peace of mind while also reducing the amount of maintenance required.

Running costs

Running costs depend entirely on how you heat your water. If your Sunamp is paired with solar panels, it can store excess electricity that would otherwise be exported to the grid. Alternatively, many owners charge their unit overnight using off-peak electricity tariffs, providing low-cost hot water throughout the day.

Traditional cylinders can also be heated during off-peak periods, but because they store hot water directly, they’ll generally lose more heat while waiting to be used.

Which system works best with solar?

This is where a Sunamp really comes into its own. Instead of exporting surplus solar electricity for a relatively low payment, you can use that free energy to charge your Sunamp and provide much of your household’s hot water.

Many homeowners combine a Sunamp with solar PV, home battery storage, and a smart electricity tariff to dramatically reduce electricity consumption.

If you’re trying to electrify your home and reduce your reliance on fossil fuels, a Sunamp fits naturally into that journey.

Installation

Replacing a hot water cylinder with another cylinder can be straightforward.

Installing a Sunamp may require some plumbing and electrical alterations, depending on your existing set-up, but the overall installation is usually completed within a day. As every property is different, it’s always worth discussing your current heating system before deciding which model is most suitable.

Which is right for you?

A traditional hot water cylinder remains a perfectly good solution for many homes, particularly if you’re simply replacing an older cylinder with a similar system. However, if you’re wanting to save space, improve efficiency, make better use of solar energy, or move towards an all-electric home, a Sunamp offers several significant advantages.

It’s particularly well suited to homeowners who want to reduce energy waste, free up valuable storage space, and take advantage of modern electricity tariffs.

The verdict

Both systems provide reliable hot water, but they do it in very different ways. Traditional cylinders have served UK homes well for decades, but they’re based on storing large volumes of hot water that gradually lose heat over time.

Sunamp takes a more modern approach by storing thermal energy instead. The result is a compact, highly efficient system that works exceptionally well alongside solar panels, battery storage, and off-peak electricity tariff.

If you’re investing in the future of your home rather than simply replacing an old cylinder, a Sunamp is well worth considering. If you’re unsure which Sunamp model is right for your household, our team is always happy to offer advice based on your property, your hot water usage, and your future plans.