  The emergence of distributed generation and the electrification of demand
have opened the possibility for prosumers to participate in electricity
markets, receiving economic benefits on their bills and contributing to the
reduction of carbon emissions, aligning with United Nations Sustainable
Development Goal 7. Consumers and prosumers can participate through implicit
and explicit demand flexibility and (collective) self-consumption. This study
analyses the potential markets in which prosumers can participate and indicates
whether these are currently open. The markets studied include day-ahead,
intraday, ancillary services, adequacy services, constraint management, and
local flexibility markets. Additionally, collective self-consumption is
analysed as a service through which prosumers can participate in the
electricity market. Previous studies are usually focused on a single market or
in a single country, making impossible a complete comparison. This analysis has
been done in Spain, Italy, Croatia, and the United Kingdom as representative
countries to obtain a methodology to assess countries' openness to prosumer
participation in electricity markets, comparing regulatory frameworks and
assigning scores based on their prosumer inclusion across various markets. This
work updates current literature reviews with the changes and a new description
of local market designs in Spain. This methodology can be used to compare other
countries' grade of openness. The results of this study show that the analysed
countries can be categorised into three groups: almost open, partially open,
and closed markets. Analysing the differences, recommendations on the following
steps to foster user participation are suggested for each group.
