Abstract This paper analyses Slovak electricity market with a focus on photovoltaic energy. It evaluates the impact of the solar electricity penetration into electricity mix on spot prices, seeks evidence of the merit order effect in the Slovak electricity market and quantifies it based on hourly data. The multivariate regression analysis covers the period 2011–2016. The rather small merit order effect estimated by an OLS time series model leads to the small decrease of Slovak electricity wholesale prices. This spot price reduction attributable to the photovoltaics does not outweigh the costs of the support scheme borne by end users what implies a consumer loss.