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Combi Boilers are often called tankless systems and never have water storage. A Combi boiler is fed with cold mains water supply and it needs a minimum pressure of 1.0 bars. They are activated by water demand in the home but they often have a pilot light. They heat water by burning gas.
Heating water for washing and other domestic uses accounts for 20% of energy use in a home, and up to 80% of homes in the UK have a combi boiler.
Adding a small water tank in the home will allow off peak electricity to be stored and the size is typically 200 to 300 litres. A typical 4 minute shower uses 6 litres of water (4 litres of hot mixed with 2 litres of cold). Adding a 210 litre tank will allow hot water storage for 12 showers and will store 12 KW/hr of off peak power reducing the gas usage in a typical home by 20%. https://showerpowerbooster.co.uk/information/what-do-you-need-for-a-good-shower/
When drawing 8 litres a minute (enough for two showers), 100% of the energy used is from stored hot water heated using surplus electricity. 100% renewable = 0% fossil fuel energy.
For potable hot water 8 litres a minute is enough for 2 showers.
Anything above 2 showers running at the same time and the process fails.
When there is no surplus electricity then the combi boiler simply reverts to burning fossil fuel taking load away from the National Grid.
Adding a simple tank in the home with a simple heat stratification devise gives an affordable energy storage tank. The ShowerPowerBooster SP2B gives the perfect fully automatic integration of any heat store with a Combination Boiler.
The diagram below shows how to integrate stored hot water with the return flow to a combi boiler using a patented ShowerPowerBooster.
