If you’re considering upgrading your hot water cylinder you will be pleased to hear there is an alternative to the greedy, bulky and inefficient traditional hot water cylinder. Most of us are familiar with the hot water cylinder, but a newer option, the Sunamp Thermino heat battery, is changing what’s possible.
How a Hot Water Cylinder Works
A traditional cylinder stores hot water itself, either heated directly by an immersion element or indirectly via a boiler or heat pump. It’s a familiar, well-understood technology, but it comes with some inherent drawbacks:
- Bulky footprint – cylinders take up significant space in an airing cupboard, utility room, or loft.
- Standing heat loss – even well-insulated tanks lose heat continuously simply by sitting there full of hot water, typically in the range of 1.4–3.3 kWh per day.
- Maintenance requirements – unvented cylinders need G3 certification at install, plus regular servicing, and are prone to limescale buildup and corrosion over time.
- Legionella risk – because a large volume of water is stored, safety checks are needed to manage bacterial risk.
How a Sunamp Thermino Heat Battery Works
A Thermino isn’t a water tank at all. It stores thermal energy in a phase change material rather than in water itself, then transfers that heat instantly to mains water as it passes through a heat exchanger. Because this material is far more energy-dense than water, a Thermino can be up to four times smaller than a cylinder delivering the same amount of hot water – often small enough to fit in a kitchen cupboard or if in an airing cupboard you get to reclaim a huge amount of space!
The benefits this brings:
- Compact size – ideal for flats, houses, retrofits, and homes where a cylinder simply won’t fit or isn’t desired.
- Much lower heat losses – because there’s no large volume of hot water sitting around losing heat, standing losses are significantly lower than a conventional cylinder. In turn this represents much lower running costs.
- Instant mains-pressure hot water – no waiting for a tank to reheat, and a consistent temperature throughout a bath fill or shower.
- No maintenance – no mandatory annual servicing on the unit itself, and minimal risk of limescale, corrosion, or Legionella since so little water is held in the battery.
- Flexible energy sources – Thermino units can be charged from grid electricity, solar PV, a boiler, or a heat pump, making them a good match for phased, budget-friendly upgrades away from fossil fuels.
Which Should You Choose?
For many homes, a Thermino heat battery offers real advantages over a traditional cylinder – particularly where space is tight, heat loss matters, or you’re planning a longer-term move to solar. That said, cylinders remain a proven, familiar technology, and the right choice depends on your property, your existing heating setup, and your budget.
The best way to know for sure is to have your home assessed by a qualified installer who can weigh up your space, hot water demand, and future heating plans, and recommend the system that will genuinely perform best for you. Cotswold Heating Solutions is an authorised, accredited installer of Sunamp products and has installed over 1000 units to date. Contact us now to receive further information or to book a free, no-obligation home survey.
