The paper analyses the cost properties of a sample
of Italian utilities providing in combination gas, water and electricity
services. The estimates from a multi-product Composite cost
function (Pulley and Braunstein, 1992) are compared with the ones
coming from other traditional functional forms such as the Standard
Translog, the Generalized Translog, and the Separable Quadratic. The
results show that the composite model provides a better description
of data and highlight the presence of global scope and scale
economies for the median firm of the sample.