In recent years, renewable energy technologies have been advocated in Fiji on the basis that they improve energy security and serve as a risk-mitigation measure against oil price volatility. Despite this, there have been no published attempts to measure the impact of renewable technologies on energy security or to assess the major threats to that security. This analysis is important if the benefits of renewable energy sources in Fiji are to be evaluated adequately. This article considers the key threats to the security of electricity supply in Fiji for grid-connected and off-grid areas and uses these as a basis for a definition of energy security that is relevant to Fiji. It proposes a method for assessing the potential contribution of renewable technologies to the security of electricity supply in Fiji, based on mean-variance portfolio theory used in financial markets.