The lower house is relatively straightforward: One coalition will end up with clear majority there because the group that gets a plurality automatically gets 55% of seats. At the moment the centre-left coalition is ahead on the vote count, but only slightly.
The Senate is way more complicated, however. There’s no clear winner and it doesn’t have the same kind of overarching mechanism as the lower house. Here’s a description from JP Morgan’s Alex White on how it works:
In the Senate, the allocation of seats takes place on a regional basis, broadly following the rules of the Lower House. In each region (excluding some small regions), at least 55% of the seats are assigned to the coalition with the plurality of votes. Other coalitions and parties that exceed certain thresholds get assigned the remaining seats on a proportional basis. There is a 20% threshold for coalitions, an 8% threshold for parties running alone and a 3% threshold for parties within a coalition in order to participate in the potential allocation of seats. In case of a distribution of votes at regional level in mainly line with the national average, the allocation of seats in Chamber and the Senate should be very similar. However, as is the case in Italy, strong regional differences in the voting patterns may create a different seat allocation in the two houses. It is worth highlighting that In terms of numbers, 315 senators are elected in total, 309 of which by residents and 6 of which by Italians leaving abroad. In addition,there are current 5 senators for life that will become 6 when Napolitano’s term as president of the Republic expires. Senators for life typically do not influence key votes such as a confidence vote. The required majority is of 158 seats excluding the senators for life.