Summary: An affine Hecke algebra \(\mathcal{H}\) contains a large abelian subalgebra \(\mathcal{A}\) spanned by the Bernstein-Zelevinski-Lusztig basis elements \(\theta_x\), where \(x\) runs over (an extension of) the root lattice. The centre \(\mathcal{Z}\) of \(\mathcal{H}\) is the subalgebra of Weyl group invariant elements in \(\mathcal{A}\). The natural trace (‘evaluation at the identity’) of the affine Hecke algebra can be written as integral of a certain rational \(n\)-form (with values in the linear dual of \(\mathcal{H}\)) over a cycle in the algebraic torus \(T=\text{Spec}(\mathcal{A})\). This cycle is homologous to a union of ‘local cycles’. We show that this gives rise to a decomposition of the trace as an integral of positive local traces against an explicit probability measure on the spectrum \(W_0\setminus T\) of \(\mathcal{Z}\). From this result we derive the Plancherel formula of the affine Hecke algebra.