Thanks @UrbanPlumber seems more than marginal on these two units, they are hitting 6kW both on 5 kW units, one is over a 7 hour period and the other a 1.6h period, there’s more in the post here Vaillant maximum output capacity testing - #183 by TrystanLea . Like I said I think it’s a bit early to be conclusive, would like to see what difference toggling the setting makes on a single unit going flat out during defrost conditions.