There are risks, however, you can do a few things to protect the owner and yourself, if you're the property manager. First, set a maximum dollar amount per month that will be covered in the lease. If the average bill is $120, then put in the lease that the tenant is responsible for anything above $130, assuming the # of occupants is similar. Also, have the owner set themselves on an equal payment plan with the utility company. That will keep them from having large spikes. Lastly, make sure to collect a large enough security deposit to cover the owner if the tenant were to move out or go way above the allocated utility amount. Obviously, you can't collect more than what State Law allows, but, if the term is at least 30 days, you can collect a security deposit equal to two months rent. Encourage the tenant to conserve energy by offering them a credit equal to what they didn't use vs. what was allocated. My property management division will include utilities, lawn care and even a set number hours of cleaning service per month depending on the tenant's needs. It is usually when working with contracted employees where their company is paying a set housing allowance.
Hope this helps.