A solar heating system costs $25,000 to install with a yearly operating cost of $300. An electric heating system costs $6,500 to install but incurs a yearly operating cost of $4,000. How many years will pass before the total cost of the solar heating system is less than the total cost of the electric heating system? Round your answer to the nearest year, if needed. Type in your numerical answer only; do not type any words or letters with your answer.