The article analyzes house price dynamics in Warsaw from 2006 to 2013, considering spatial relationships. Researchers used a new method combining geographically weighted regression and penalized spline regression to better understand how time affects prices. This approach resulted in a more accurate measure of time effects and improved goodness-of-fit statistics. The study introduced a robust hedonic index that is less affected by short-term price changes, showing how interest rates and housing policy impact house prices in Poland.