This work aims to quantify the effect of the ongoing increase of the solar photovoltaic (PV) electricity production to the economic feasibility of residential PV systems in Finland. Due to the lack of feed-in tariffs for PV, the sensitivity of the hourly electricity spot price in the Nordpool day-ahead market for the Finland (FI) market area towards increasing PV production is a key factor when predicting the profitability of the residential PV systems. Due to the weather-dependent power production profile, PV is vulnerable to the cannibalization effect: the drop of the PV electricity value due to high PV production. A regression model applied to the year 2023 data of the Finnish power system identifies the effect of different predictors with the electricity spot price, thus quantifying the cannibalization effect. The parametrized model enables producing synthetic electricity spot price profiles with different PV capacities. These profiles allow calculating the annual value of the produced PV electricity for residential PV systems. The additional value created with a 4 kWp vertical bifacial PV system compared with equally sized, conventional, southfacing and tilted monofacial PV rises from 14% to 25% when national PV capacity rises from 1000 to 5000 MWp.