This study investigates the desalination needs and available technologies in Sri Lanka. Lack of rainfall, pollution due to agricultural chemicals, presence of fluoride, increasing demand, exploitation of ground water and brackishness have created scarcity of fresh pure water specially in near costal and dry zones in Sri Lanka. Due to Cronic Kidney Disease (CKD) around 500 people died in dry zones annually which is suspected to cause by Arsenic and Cadmium contain in ground water due to agriculture chemicals.   The available desalination methods are Reverse Osmosis (RO), Solar distillation and conventional methods. The cost for RO is Rs.0.10 cents per liter and solar distillation Rs.2.96 per liter. Although the price shows that the RO is better but due to high initial investment as a third world country it is very difficult to afford huge initial investment without government intervention. The experimental solar desalination units only produce nearly 5liters of potable water per day and directly impacted by availability of solar radiation. The energy availability of Sri Lanka and future potable water demand predicted as 2188.3 Mn liters as maximum demand which will be in 2030, therefore by that time the government should have a proper plan to cater the demand and desalination plants need to be planned and built based on the demand of dry zones and specially agriculture areas.   The applicability of renewable energy for desalination in local arena was also simulated taking the Delf Reverse Osmosis plant for the simulation. Results show that the optimum design is combination of Solar PV and existing 100kW Diesel generator Set with Battery bank and converter.