Electricity Endesa. Endesa is the biggest electricity company in Barcelona. Usually if you are buying or renting an apartment in Barcelona, you will have to either open an account or change the present account details for the electricity supply. This can be done by telephone. You will need the contract number if there is an existing account. The meter will usually be read when you take over the apartment. Sometimes in rented flats the owner prefers that the account name stay the same and the new tenant just changes the bank account number, so the the Electricity bill is paid automatically by the new tenant's bank. Visit the Endesa website for more information and contact numbers. The website is in Spanish and Catalan only. The customer service number for Endesa clients is 800760333. The monthly Endesa electricity invoices are very complicated to understand, so Endesa have made a webpage to help explain the invoice with itemized explanations to help you understand how the electricity bill is calculated. Contact telephone for Endesa in Barcelona is free phone number 800760333 or 800760706 for emergencies. TO contact Endesa from outside Spain use the Endesa online office service