Lances were relatively thin and long (details in the article), comparable to lances on these frescos. Tested lances were made of solid pine wood (presumably Scots Pine, since article was of British origin). With lance rest impact energy can go over 250 joules, however at 250-260 joules lances started to break. This added energy seems to be in ballpark of up to 110 joules which in turn is in ballpark of 2.5 kilograms of added weight via the skill of the rider. According to following scientific paper, couched lances without lance rest (gadget on plate armor) can achieve up to 230 joules of KE, this is combination of ballistic properties of the lance and skill of the rider the can put some weight into the lance. Damage of couched lances with RBM combat module equals joules of kinetic energy of such attack.
