Evolution of the radius of non-accreting and accreting young Sun models calculated with the 1D stellar evolution code. The non-accreting model is shown as the black line. Coloured curves indicate accreting models with a rate Ṁ = 10^-4M_⊙ yr^-1 assuming different treatments of accretion: cold accretion (red dash); hot accretion assuming uniform redistribution within the stellar interior of the accretion energy rate L_add with α = 0.2 (magenta dash-dot ); hot accretion assuming an accretion boundary condition L_surf = L_add with α = 0.2 (blue dash) and α = 0.3 (green dot).