The European day-ahead market is characterized by different types of orders and rules, such as block orders and the uniform purchase pricing rule. Block orders are present in many central and northern European countries, whereas the uniform purchase price is enforced in the Italian market under the name of Prezzo Unico Nazionale (PUN). In this paper, we analyze the effects of introducing block orders into the Italian market. In particular, we assess how block orders could affect the computation time, the PUN level, and the number of paradoxically rejected orders. The analysis is performed by varying five main determinants, represented by the total number of blocks, the demanded/offered quantity, the block timespan, the block location, and the demand/supply ratio. Numerical results are obtained by using real Italian market data.