There are several types of incinerators of municipal solid waste (MSW). Its efficiency will depend of the type (MassBurn Incineration- MBI, Fluidized bed incineration- FBI and modular incineration). The amount of energy obtained from MSW will also depend on: a) the low calorific value of MSW, which is also function of the non-organic residues content; b) the humidity content.
Typical efficiencies of the heat recovery system from hot gases are between 7 -19%. Some plants have back-up with fossil fuels.
In general terms, I think that a global energy conversion efficiency (heat to electricity) of around 18.5% is typical for MBI incinerators of medium to large scale.