Work on fixed installations (faste installationer) has to be done by an autoriseret elinstallatørvirksomhed (authorised electrical firm). Ask whether they hold the authorisation themselves or bring someone who does, and get that on the invoice.
Esbjerg is more houses and industry than tight apartment blocks. Wind on the west coast affects roofs, facades and outdoor work more than in eastern Denmark. The same 2 businesses as the Danish page: Høgholm ApS, E Electric ApS.