Hi Sharon, thanks for the feedback, glad it’s helping.
For E7 or E10 systems I’d always recommend having a friendly heating engineer or electrician check it out, as there are various different ways the systems can be put together. So there’s no ‘standard’ answer unfortunately. Hot water storage could mean one of two things: a) hot water for use in your hot taps (ie running water) or b) hot water to be pumped round your heating system (ie energy storage). The second, (b), is great for use with E10. The key to saving money with E10 is if you can shift your electric load into the off-peak times. If you also need to run your heating during the peak (expensive) times then you’ll need to crunch the numbers to check if it works out cheaper or not.