This hotel is a member of the Sol Melia group of hotels and I have been a member of their loyalty programme for several years.
I struggled to give this hotel an "average rating" for several reasons. But its worst failing is the problem of parking. They do not have their own car park and have to use the closest town public parking where they have reserved spaces BUT as far away as possible from the hotel and on menos 5 level of the car park. There is a lift which takes one to the surface about 25 metres from the entrance to the hotel but across a busy road - however one has to walk underground for about 300 hundred meters to reach the lift. This problem makes it very difficult for those arriving/leaving on Brittanny Ferries in their vehicles.
Breakfast is served in the cafeteria on the ground floor but there is no table service and and you have to serve yourself from the adjacent bar - you should be warned that the breakfast is not very generous, certainly not in comparison with other Tryp hotels I have stayed at in Spain - in San Sebastian and Jerez de la Frontera, for example.
The rooms are reasonably comfortable and the bathrooms clean and well appointed but a "face lift" is needed. WiFi is free.
The Tryp Arenal has a three star rating, but who awards these ratings. I think it is a 2.5 rating at best. I don't think I'll stay here in the future. But then I'm only in Bilbao to catch the ferry!

This hotel has an excellent location and kind staff, gives however an impression of uncleanliness
and seems kind of old and tired.

We stayed here as part of a Rick Steves tour. There were three of us, so we had one double and a single. The double was much nicer than the single I had. The paint was tired, the window opened onto an open shaft, and the AC didn't work at all. The room reeked of cigarette smoke. Of the five hotels we have stayed in during our trip, this was by far the worst. The location, though, was convenient. We were right on the edge of the old town, and minutes from the train station.

Charming hotel. Located in the historic area (Casco Viejo) of Bilbao, near the beautiful pedestrian streets. The hotel is close to tourist attractions and it’s a pleasure to walk down from the hotel and Stroll the area on foot. Rooms are not luxurious but clean and warm and give a good feeling. At first we were offered a room in the loft of the hotel, but the room was stuffy, and with a sky light Window only. We asked to Switch rooms and the kind receptionist gave us a room with a large window overlooking the lovely street (near the Arriaga Theatre). We arrived to Bilbao for the BBK music festival and had a great time in the city-Especially this part.