Depending on the actual shape of the house, the elevation of the terrain and the effect you want to achieve, a projector installed 20-25 ft away could be enough. Each projector covers 625 square feet, but it all depends on the way your house or yard looks like.
Divide 625 by the height of your house and you will find out how far away you need to place the projector. For example 625/20=31.25 ft away from the walls. If there are any obstacles such as fences or trees it is advisable to get more than one laser christmas projector.