Can you use it if you have led Christmas lights on house?

Yes, the only problem will be that the spots nearest to the lights will look really washed out. The laser lights are bright on their own and for an elegant effect we would advise to use only projector lights on the same surface, or it would look crowded.

However, if you have a particular setting in mind you can still use old fashioned Christmas lights in combination with the stars.

Also, consider that the projector lights are designed to the highest and most recent safety standards, for outdoor use, while most Christmas LED lights use old, possibly dangerous technology.