Sunamp Thermino vs Hot Water Cylinder: Which Should You Choose?

Why compare a Thermino heat battery with a hot water cylinder?

Hot water cylinders remain a familiar and widely used way of storing domestic hot water in UK properties.

But a cylinder needs enough physical space to store the required volume of water, and heat is continually lost from the stored water through the insulation surrounding the cylinder.

For many properties this is entirely manageable. In others – particularly apartments, smaller homes, renovations and projects where cupboard or plant-room space is valuable – the size of a conventional cylinder can become a significant design constraint.

Thermino approaches thermal storage differently.

What makes a Sunamp Thermino different?

Instead of using a large body of water as the primary thermal storage medium, Thermino uses Sunamp's Plentigrade phase change material.

The material absorbs thermal energy as it changes phase and releases that stored energy when hot water is required.

Mains water passes through the heat battery and picks up the stored thermal energy before being delivered as hot water.

If you would like a detailed explanation of how this works, see What Is a Sunamp Thermino Heat Battery and How Does It Work?

Sunamp Thermino vs hot water cylinder

The differences are easier to understand when the two approaches are compared side by side.

1. Thermino can free up considerably more space

Space is one of the strongest reasons to consider a heat battery.

Sunamp states that the Thermino ePlus can be up to four times smaller than the hot water cylinder it replaces, thanks to the energy density of its Plentigrade phase change material.

This can make a significant difference in a home where a large airing cupboard is currently occupied by a cylinder.

It can also give architects, developers and retrofit designers more freedom when floor area and storage space are limited.

2. Thermino is designed for very low heat loss

Any thermal storage system loses some energy while heat is being stored.

Sunamp's current UK technical data lists standby heat losses for Thermino ePlus models ranging from approximately 0.48kWh to 0.84kWh per 24 hours, depending on model size.

Sunamp describes the range as offering ultra-low heat losses and states that Thermino can achieve substantially lower heat loss than older conventional cylinders.

This does not mean every Thermino will automatically use less energy than every modern hot water cylinder. Cylinder specification, size, insulation, usage and charging strategy all affect the comparison.

3. Compact size does not mean low hot water capacity

A common question is whether a smaller heat battery can provide enough hot water for normal household use.

Thermino models are specified using equivalent hot water cylinder sizes, making it easier to compare their stored thermal capacity with conventional systems.

The Thermino ePlus range is designed to provide high-flow mains-pressure hot water, but choosing the correct model remains essential.

Household size, number of bathrooms, showers, baths, expected flow rate and usage pattern should all be considered when specifying the system.

4. Does a Thermino provide unlimited instant hot water?

No stored-energy hot water system should be described as providing unlimited hot water.

Thermino stores a finite quantity of thermal energy. Once that stored energy has been used, the battery needs to recharge.

The important point is that the correct Thermino model should be selected to match the property's expected hot water demand, just as a conventional cylinder needs to be sized correctly.

5. Thermino can make better use of off-peak charging

Thermino ePlus uses grid electricity and is designed with the ability to shift charging into off-peak periods.

When paired with an appropriate electricity tariff, this means thermal energy can be stored when electricity is cheaper and used later when hot water is required.

The actual financial saving depends on the electricity tariff, charging schedule and household hot water use, so off-peak charging should not be presented as guaranteeing a particular saving.

6. Thermino ePlus can work with solar PV

For properties with solar panels, Thermino ePlus can be configured to make use of surplus solar-generated electricity using the appropriate Optimino PV key and compatible diversion control.

This creates the opportunity to store some surplus solar energy as heat for later hot water use rather than exporting all available surplus electricity.

How much solar energy can actually contribute depends on the PV array, season, weather, household electricity demand and hot water use.

For buildings already using electric heating, this can form part of a wider all-electric energy strategy. You can explore this approach further on Infrared Heating and Solar PV.

7. Thermino works particularly well in an all-electric property

If a property is moving away from gas, both space heating and domestic hot water need to be considered.

Infrared panels or bar heaters can provide electric space heating, while Thermino ePlus can provide an electrically charged thermal store for domestic hot water.

This allows the two systems to operate independently without requiring a gas boiler for either space heating or hot water.

For buildings without gas, you may also find Is Infrared Heating a Good Option for Buildings Without Gas Supply? helpful.

8. What maintenance does a Sunamp Thermino require?

Sunamp states that the Thermino ePlus heat battery itself has no mandatory annual maintenance requirement.

However, that should not be interpreted as the entire hot water installation requiring no maintenance.

Sunamp specifies mandatory plumbing components including an isolation valve, pressure reducing valve, expansion relief valve, expansion vessel or shock arrestor and thermostatic mixing valve. A water conditioner is also required where applicable according to water hardness.

These components need to be installed and maintained in accordance with the relevant manufacturer requirements.

Correct professional installation is therefore important for both performance and warranty compliance.

9. Is Thermino suitable for retrofit projects?

Yes. The compact dimensions can make Thermino particularly useful where an existing cylinder is taking up valuable space or where a conventional replacement cylinder would be difficult to accommodate.

It can be considered for:

• Existing homes replacing direct electric hot water cylinders
• Apartments where cupboard space is valuable
• Properties moving away from gas
• Renovation and retrofit projects
• Projects incorporating solar PV
• New-build all-electric properties

Installation still requires appropriate plumbing, electrical provision, commissioning and enough physical access for the selected model.

When should you choose Thermino – and when might a cylinder still make sense?

Who should consider a Sunamp Thermino?

Thermino is particularly worth considering when the limitations of a conventional cylinder create a genuine problem for the project.

That might include:

• Homes where an airing cupboard could be reclaimed
• Apartments with limited storage space
• New-build electric-only homes
• Properties moving away from gas
• Retrofit and renovation projects
• Homes using off-peak electricity tariffs
• Properties with solar PV or plans to install it

Frequently Asked Questions

Sunamp Thermino vs Hot Water Cylinder: The Bottom Line

A traditional hot water cylinder remains a perfectly viable hot water solution, but Thermino offers a fundamentally different approach to thermal storage.

Its strongest advantages are compact dimensions, low standby heat losses, mains-pressure hot water and the ability to integrate off-peak electricity and solar PV into an all-electric hot water strategy.

For a property where space is valuable, a conventional cylinder is difficult to accommodate, or the goal is to build a modern all-electric energy system, a Sunamp Thermino can therefore be a particularly compelling alternative.

The key is correct specification. Choose the Thermino model around the property's actual hot water demand rather than simply replacing a cylinder based on its physical size.

Next Steps

You can view the available models and accessories in the Sunamp Thermino ePlus Heat Battery collection, or speak to our team for guidance on specifying the right system for your project.