Can an Excel spreadsheet stored in Sharepoint 2013 be edited in the browser using the Excel web app?

Hi,

In skydrive or Office 365, I'm able to save an Excel spreadsheet, and open it for editing in the browser. But in a Sharepoint 2013 server installed on-premise, I am only able to open it in read-only mode in the browser. I order to edit it, I am having to download the file and edit in Excel on the pc.

Is there some setting in the Sharepoint 2013 server that will allow the Excel web app to edit the file in the browser?

Thanks,

Sam