Britney Spears' San Fernando Valley Winter Wonderland

1215_brintey_house_AKMBack home from her whirlwind world tour, Britney Spears has decked the halls of her brand new L.A. mansion with boughs of holly ... and tons and tons of colorful Christmas lights.

The 30-year-old singer has spared no expense to get into the festive light-everything holiday spirit -- casting a bright glow across her stuffy ultra-exclusive San Fernando Valley neighborhood.

All Brit Brit really wants for Christmas is ... a huge electric bill. Clark Griswold would be proud.

Fa la la la la la la la laaaa.