Certain customers have two separate utilities providing them service; one utility that generates the electricity and another that transmits and distributed it to the customer's home. These customers might have two separate tariffs, one from each utility. To combine tariffs, select the option as shown below.
Clicking on this option would open a pop-up asking you to add two json files. Once you have loaded the two json files, the Tariff Builder/HOMER Grid application will combine the rates from both tariffs.
The next step is to decide if "..the combined tariff represent the costs from both the electricity provider and the distribution utility". If you click "Yes" to this question, then this combined tariff represents the full set of charges for the customer, including both generation and distribution. If you click "No" to this question, then this combined tariff is still not complete and includes only the charges from the distribution tariff. In this case, you will have an additional step after loading the combined tariff into your model. See "Electricity Provider Rates" for more information on this.
You can verify if tariff loaded into your model has the rates from both tariffs by clicking on the respective tabs to view the list of rates.