u/randomnameipicked

Looking at surveys and quotes from both installers, both quoted for heat loss/radiator output requirements in dt50. Is this appropriate? HG still quotes a 400% efficiency , though I was under the impression we should be looking at dt30?

Also, does it sound right that HG can achieve higher efficiency by only changing the hot water tank capacity, from 210l to 300l? For 4 occupants 300l sounds a bit too big?

Thanks!