The UK ended its involvement with the bloc at the end of January. Currently, the arrangement remains much the same, with the free movement of goods, services, and people still possible. The UK also remains part of the internal energy market.
However, 2020 sees the UK enter a transition period that will see it negotiate its future relationship with the EU.
The new rules, whatever they may be, are due to take effect on 1 January 2021.
WindEurope said it "[doesn't] anticipate new tariff barriers if a deal can be reached", but warned that "even allowing for a starting point of convergence, 11 months is an extremely tight deadline for agreement".
The lobby group is also concerned about the impact Brexit could have on the UK's status as the leading offshore wind market.
"The UK remains the world's largest offshore wind market. But the European Commission has taken a hard line on future UK participation in the North Seas Energy Forum. This could have a negative impact on the deployment of offshore wind in Europe – one of the touchstones of the energy transition," WindEurope said.