What size Sunamp do I need?

Choosing the right Sunamp heat battery size comes down to one thing: how much hot water your household actually uses day to day.

Sunamp Thermino heat batteries come in four main sizes: 70, 150, 210 and 300. These sizes correspond to the capacity of hot water cylinder that they replace. Thanks to their compact, modular design, Sunamp units can deliver the same hot water performance as much larger cylinders, while taking up significantly less space.

Sunamp size guide at a glance

Model	Equivalent Hot Water Cylinder Capacity	Equivalent Energy Storage	Typical Property Size
70	70L	3kWh	1 bed
150	150L	7kWh	1-2 bed
210	210L	10kWh	3 bed
300	300L	13.5kWh	4+ bed

 

Sunamp sizes explained

Each model is designed to suit a different level of household demand. The right choice depends on how many people live in your home, and how your hot water is used.

The Sunamp Thermino 70 is the smallest option, and only available in the ePlus range. This is typically suited to a one bedroom property with very low water demand. The Thermino 70 provides the equivalent of 70L of hot water storage, which is around 3kWh of thermal energy.

The Sunamp Thermino 150 is a common choice for smaller homes and flats. It typically suits one to two bedroom properties, providing the equivalent of 150L of hot water, or around 7kWh of energy storage.

The Sunamp Thermino 210 is designed for average family homes, usually with three bedrooms. It offers the equivalent of 210 litres, or around 10kWh of storage, making it suitable for households with more regular or overlapping hot water use.

Finally, the Sunamp Thermino 300 is the largest option available and is typically used in homes with four or more bedrooms. It provides the equivalent of 300 litres of hot water storage, or around 13.5kWh of energy capacity, and is ideal for higher demand households.

Why household size is only part of the story

While the size of your property is a useful starting point, it doesn’t necessarily tell the full story. Tow homes with the same number of bedrooms can have very different hot water needs.

For example, a couple in a two bedroom who take staggered showers will use far less hot water than a family of four who all shower within an hour in the morning. This is why your usage patterns are just as important as household size when choosing the right Sunamp.

Showers, baths, and peak demand

The biggest factor in sizing your Sunamp is not how much hot water you use in a day, but how quickly you use it.

If your household uses showers at different times, a smaller unit may be perfectly adequate. The system has time to recharge between uses. However, if multiple people are showering back-to-back or if you regularly run baths, your peak demand can significantly increase. In these cases, it’s better to size up to avoid running out of hot water at busy times.

Solar and time-of-use or smart tariffs

If you’re pairing your Sunamp with solar panels or a time-of-use electricity tariff, sizing up could be a good decision.

A slightly larger unit allows you to store more energy when it’s cheapest or when your solar system is generating. Instead of exporting surplus solar generation for a low return, you could convert it into usable hot water for later in the day.

Getting the balance right

There is no ‘one size fits all’ answer, but there is a simple rule of thumb that helps guide most installations.

If your home has lower demand or predictable usage, the smaller models like the Thermino 70 or 150 will usually be sufficient. If you have a busy household, overlapping showers, and higher water demand, stepping up to the 210 or 300 could be the better long-term choice.