The present application relates to a vacuum solar thermal panel (1) of the type comprising: a vacuum-tight envelope (10), having at least a front plate (11) transparent to solar radiation and a support structure (12) for said front plate (11); heat-absorbing means enclosed within said vacuum-tight envelope (10); and main getter means for keeping a vacuum condition within the vacuum envelope (10); wherein the vacuum solar thermal panel (1) further comprises a pressure indicator spot (13) of reactive material deposited on an inner side of said front plate (11), said reactive material undergoing a reaction noticeable from the outside of the vacuum-tight envelope (11) when the pressure within said envelope exceeds a given threshold.