I have a similar situation, but I rent out a garage apartment which is next to my house. The internet service and TV streaming service is shared between both the house and the garage apartment. I use both services every day. Renters use both services when the garage apartment is occupied. My question is how do I calculate how much cost for each service to allocate to the rental (i.e., deduct from my taxes). Certainly both services are not fully deductible since I use them for personal use too.
use any reasonable method you can come up with. there is no correct answer in your situation. in theory it could be the number of hours the tenant uses the service as to the total hours of usage but you probably don't monitor the usage.