At Rose Cottage in Oxfordshire, Gareth and his family were looking to cut their energy bills and transition away from gas. With a powerful solar PV system already in place and plans to fit a heat pump, they wanted a reliable hot water solution that could maximise their renewable generation.
The challenge – a hassle-free hot water cylinder replacement
Gareth’s 300-litre hot water cylinder failed just three days before he was due to fly to Australia, leaving the family with no hot water and very little time to act. He had already been researching Thermino heat batteries, but the situation had become urgent.
The replacement for Gareth’s broken cylinder needed to be installed immediately, with no disruption to the family’s plans. He was looking for something which would be compatible with his large 12kW solar PV array and a future heat pump, while providing a reliable hot water supply to meet the family’s demand. Lowering their household energy bills was also a priority, with Gareth looking to reduce outgoings in preparation for retirement.
The solution – a Thermino heat battery for solar hot water
Sunamp installation partner Ecosmartheat stepped in immediately, fitting a Thermino the next day and restoring hot water after just 24 hours without it. The unit was brought in on a stairclimber and installed neatly in place of the old cylinder, instantly freeing up space in the utility room.
The Thermino now works seamlessly with Gareth’s solar PV system. Because the array can only export 6kW, excess generation is automatically diverted into the Thermino via the myenergi Eddi diverter and used to provide hot water on-demand.
Since having the Thermino installed, Gareth has also switched to a Daikin air to air heat pump – another big step towards a gas-free home. The heat pump has the added advantage of providing air conditioning as well as heating, something which is increasingly important as summer temperatures in Oxfordshire consistently top 35°C.
The benefits – reliable performance, lower bills and a path away from gas
Gareth was certain that a Thermino would be a good move, having modelled performance before making the switch.
To prove how the system worked in practice he built Decarbonarma, an online monitoring platform showing real-time solar consumption, hot water charging and savings from the Thermino. Gareth is pleased to report that the data confirms what he modelled in theory – the heat loss, thermal capacity and efficiency reliably match the expected specifications.
During the 24-day period shown in the graph below, the Thermino charged fully on 12 of the 24 days without any overnight top-up – demand was covered entirely by solar generation.
Even on the days where overnight top-up was required, this was minimal, with solar covering 93.3% of total hot water demand.
This is a typical scenario as Gareth estimates around 90% of Rose Cottage’s hot water now comes from solar energy. The remaining 10% comes from off-peak electricity – resulting in hot water which is “almost free”.
Installing the Daikin heat pump has also made a big difference, cutting the family’s heating bills by £100-£150 a month and keeping gas consumption to a minimum. In fact, Gareth’s solar array now covers almost all household energy consumption including hot water, heating and charging two electric vehicles.
Switching to a Thermino has brought other benefits for the family too. They’ve never run out of hot water despite high usage, and replacing the bulky old hot water cylinder has freed up space and improved the look of their utility room.
Gareth said, “The great thing about it is that it’s quite a simple system. We didn’t want anything too complicated and the Thermino does exactly what it says on the tin. The thermal capacity to retain heat is unbelievable, the heat losses are as low as promised and there are no moving parts, so not much that can go wrong. It just works.”
"The great thing about it is that it’s quite a simple system. We didn’t want anything too complicated and the Thermino does exactly what it says on the tin. The thermal capacity to retain heat is unbelievable, the heat losses are as low as promised and there are no moving parts, so not much that can go wrong. It just works."
Gareth, Rose Cottage homeowner