The recent steep decline in the cost of PV panels and wind turbines provides an opportunity to utilise Hybrid Renewable Energy Systems (HRES) to fulfil thermal loads as well as the electrical demand. Two coupled system architectures are proposed and studied along with the base case of uncoupled architecture for comparison. The coupled systems include wind turbines, PV panels, battery bank, diesel generators (DG) or diesel-based Combined Heat and Power unit (CHP), boiler and thermal storage tank. Adopting a full factorial design of the experiment approach for each architecture, the optimum system is determined for a variety of combinations of the major influencing factors, namely, renewable resource intensity, thermal-to-electrical demand ratio and price of diesel fuel. Statistical analysis is conducted to investigate the effects of each factor on the cost of the system. The optimisation and statistical analysis show that, based on current prevailing components prices, an integrated system, which utilises excess electricity for fulfilling thermal loads, is cheaper than the base case with or without CHP unit.