Renewable energy sources (RES) are getting closer to grid parity within interconnected systems while their use in isolated and remote areas is already cost competitive with conventional generation. In mini-grids, isolated and far from the grid, the economics of different technology options (e.g. pure solar photovoltaic (PV), wind, concentrated solar power (CSP), and open cycle gas turbine (OCGT)) with different amounts of added capacity is assessed to allow the peak demand to increase by 5 MW (or 5%) and 10 MW (or 10%). This assessment is based on keeping the system reliability (measured in loss of load expectation, LOLE) at the same level as it was before the addition of conventional and renewable generators. An effective load carrying capability (ELCC) increase by 5 MW (or 5%) can be realized by adding a 5 MW OCGT or 10 MW PV and 10 MW wind. An ELCC increase of 10 MW (or 10%) requires either 11 MW OCGT or 7.2 MW OCGT, 2.7 MW PV, and 8.1 MW wind. In both cases, the solution with RES has 8% and 4% lower annual costs than the OCGT only solution (assuming crude costs of $40/barrel). From an economic and system reliability perspective, systems with low growth rates (<5%) in peak and energy demand could focus on adding RES capacity while systems with higher growth rates (>5%) still need to incorporate conventional generation.