You are allowed to deduct the cost of utilities used in rental activity if they are ordinary and necessary.
However, the IRS is strictly against mixing personal and business expenses.
For example, a mobile phone used solely for rental activity is deductible, but the base rate on your primary telephone line is considered a personal expense and is not a legitimate deduction for your rental activity.
You cannot deduct any part of the cost of the first phone line even if your tenants have unlimited use of it. If you install a second phone line strictly for your tenants’ use, all of the cost of the second line is deductible as a rental expense.