As an agent and property manager I rent houses often. Most of the time the tenant will pay for gas, electricity, water/sewer, and trash. The owner generally keeps on paying for the gardener to guarantee the lawn is maintained. In cases where the house is priced high and it is not renting, you can drop the price or offer to pay gas or electricity.
When an owner pays a utility bill I have found that it is generally higher than when a tenant pays the bill. The tenant is has more of an awareness and interest in keeping the costs down when they are ultimately footing the bill.
If your current lease does not require your tenants to pay the utilities, I don't think there is too much you can do this time around.
All the best,
Wellman Realty Company
the party using the utilities pays the utilities.
On rare occasions, a landlord will pay some utilities.
Harold Sharpe - Broker
So Cal Homes
California Department of Real Estate Broker License # 01312992