We study the long-time behaviour of the solutions to Smoluchowski coagulation equations with a source term of small clusters. The source drives the system out-of-equilibrium, leading to a rich range of different possible long-time behaviours, including anomalous self-similarity. The coagulation kernel is non-gelling, homogeneous, with homogeneity
γ
⩽
−
1
, and behaves like
x
γ
+
λ
y
−
λ
when
y
≪
x
with
γ
+
2
λ
>
1
. Our analysis shows that the long-time behaviour of the solutions depends on the parameters γ and λ. More precisely, we argue that the long-time behaviour is self-similar, although the scaling of the self-similar solutions depends on the sign of
γ
+
λ
and on whether
γ
=
−
1
or
γ
<
−
1
. In all these cases, the scaling differs from the usual one that has been previously obtained when
γ
+
2
λ
<
1
or
γ
+
2
λ
⩾
1
,
γ
>
−
1
. In the last part of the paper, we present some conjectures supporting the self-similar ansatz also for the critical case
γ
+
2
λ
=
1
,
γ
⩽
−
1
.