Sunamp, the heat battery manufacturer, has added low-power models to its Thermino range of thermal stores for hot water, launching them at ISH in Frankfurt on 18 March 2025. The new units have a heating element capacity of 1800 watts, alongside existing models rated at 2800 watts at 230V, 50 Hz1.
The company said the low-power versions were developed for the Italian market, where homes may have fuse ratings as low as 16A, giving a total supply of 3kW. Reducing charging power below 2kW allows the batteries to serve those homes, and Sunamp also names holiday lodges and park homes, which often have a 16A supply, as applications where incoming power capacity is limited1. Charging more slowly increases charge time by one third, but Sunamp states the energy content of the products is unchanged, so the volume of hot water available on tap stays the same1.
The low-power option is offered in both Thermino models: the ePlus, described as a space-saving alternative to direct hot water cylinders, and the xPlus, which replaces traditional indirect and heat pump hot water cylinders1. Thermino batteries use Sunamp's Plentigrade phase change material and are stated to be up to 4x smaller than the equivalent hot water cylinder. They can store energy from renewable and non-renewable sources, take grid electricity during off-peak periods when tariffs are lower, and release it as mains pressure hot water at a constant temperature on demand1. The new models remain compatible with solar PV diversion controllers including my-PV, Elios4you from 4-noks and myenergi eddi1.
"Sunamp thermal batteries are engineered for easy installation and operation and fit a variety of settings so I'm delighted that we can now offer even greater choice. The new low-power options are ideal for homes with lower fuse ratings."
The 1.8kW alternative is also available to Sunamp's OEM and White Label partners, according to Maurizio Zaglio, the company's global head of partnerships1. Low-power Thermino thermal storage is now available through Sunamp authorised distributors1. No UK-specific pricing, eligibility or installation figures were given in the announcement.
| Model | Element capacity | Stated role |
|---|---|---|
| Thermino ePlus (low power) | 1800W | Space-saving alternative to direct hot water cylinders |
| Thermino xPlus (low power) | 1800W | Replaces traditional indirect and heat pump hot water cylinders |
| Existing Thermino models | 2800W at 230V, 50 Hz | Existing range |
Why it matters for households
A heat battery stores heat rather than keeping a cylinder of hot water standing ready, and the practical constraint on fitting one has often been the electrical supply available to the property. A home with a 16A fuse, or a lodge or park home on a restricted supply, could previously struggle to run a unit drawing close to 3kW. A model that charges below 2kW widens the set of homes where a heat battery can be installed without an electrical supply upgrade, which is the point at which a household's hot water stops depending on a gas connection or a large stored volume. The trade-off is slower charging, which matters most where a household wants to refill the battery within a short off-peak window or a short spell of surplus solar generation. For homes weighing a battery against a conventional cylinder, the comparison turns on space, recovery time and how the unit is charged; the differences between a heat battery and a hot water cylinder set out those trade-offs. Because the low-power models work with solar diversion controllers, they can also absorb surplus generation from a rooftop array, a route that connects to heat pump and wider emerging technology decisions in a home.
What happens next
The low-power Thermino models are available now through Sunamp authorised distributors, and through the company's OEM and White Label partners1. No UK launch date, price or installer certification details beyond that were reported.