A Home Insurance excess is the amount you will have to pay towards a claim. This usually consists of a voluntary excess (this is something you can choose when taking out a policy) and a compulsory excess which is set by the insurer. You would need to pay both the voluntary and the compulsory in the event of a claim.
The voluntary excess you choose may affect your premium. A lower excess means your premium may go up in price and if you choose a higher excess, this may bring your premium down. Please remember that the excess you choose, is what you will have to pay in the event of a claim.