1 According to the Fire Protection Research Organization's 2009 Fire Sprinkler Cost Assessment, sprinkler installation costs homebuilders $0.38-$3.66 per sprinklered square foot, with an average cost of $1.61 per sprinklered square foot.2  For an average 2,200-square-foot home, expect to pay about $3,542. For a 3,500-square-foot home, expect to pay about $5,635. 2  Fire sprinklers cost 1%-2% of the cost of a new home. 3  In already existing properties, sprinkler systems typically cost $2,000-$16,000.