We've had a Mega Flow tank that works alongside combi boiler for the last 7 years. It's attached to a timer that also does the heating. I've always had it set to heat the water twice a day but I'm wondering if that's the most cost effective solution? Gas engineer told me it was cheaper to have it on all the time but that doesn't sound right to me. Obviously with gas bills through the roof I'm looking for the cheapest solution.