From 2010 many countries are changing their power generation mix from hydro and fuel-fired generators to hydro, wind and solar energy. In Uruguay's case, in the first quarter of 2017, the installed wind capacity exceeded the average energy load. Uruguay is an example of a working system with a great amount of Variable Energy Resources (VER). This work shows how the optimal operation of the system is programmed on a weekly, daily and hourly basis to deal with the VER. The way the forecast of the wind, solar and hydro resources availability are considered and how these uncertainties are used to generate a Spot Signal Price (SSP) that may be used to implement a Demand Response pricing scheme is shown. The developed tool is called VATES and it is running continuously on ADME's servers. The forecast of the dispatch for the next 72 hours is continuously available at http://vates.adme.com.uy