Viessmann integration and switching boiler to use electric for DHW during cheap periods

Hi All

Recently setup the viessmann integration on HA , I’m considering buying a smart switch for our megaflow water cylinder to heat hot water (DHW) when our electricity becomes cheap overnight rather than use gas from the boiler.

I can see there is a HA switch for DHW to turn it on and off. Wondering if anyone has tried this method with success? I have octopus agile here in the uk, and we occasionally get negative pricing, so would like to take advantage of those periods for the hotwater.

Thanks alot