This is for an eHW 9 Heat Battery heated by renewable grid electricity.
Heated anytime vs heated overnight on ultra cheap tariff.
Heat battery insulation is exceptional, so any heat stored overnight will still be there the following evening. Heat batteries don’t suffer from the cooling effect of fresh cold water entering to replace hot water drawn off, thus cooling the whole of the water in the tank.
Over 10 years the hot water heating savings are (£296 x 10) £2960.00
Size 9 mains pressure tank vs a 210 litre mains pressure tank.
Annual service of a mains pressure tank £75.00 vs No annual service for a Heat Battery.
This calculation is not taking in to account the lower heat loss compared to a mains pressure tank that will further add to your savings.
Mains pressure annual service is £75.00
Total savings of a heat battery heated via off peak over night electricity compared to a mains pressure tank heated on a normal tariff over 10 years is £3710.00, paying for itself very quickly.
* Actual savings will depend on how you use your water and how you charge the battery - there are so many possibilities.