In response to variation generation of renewable resources, it is necessary to assess the impacts on electricity demand characteristics. Renewable resources under consideration are photovoltaic, wind, small hydro, biomass, and biogas. It is proposed to treat renewable generation as negative load. Electricity demand is characterized by using peak demand, energy demand, and load factor as well as it is divided into three groups: peak, intermediate, and base. Variation of renewable generation is expressed through a concept of net load. Changes of demand characteristics can be analyzed from annual and seasonal changes of load duration curves after integrating renewable resources. The impacts on demand characteristics and load groups have meaningful implication on operating costs. Numerical results were obtained by using hourly load data and generation portfolio of Thailand. © 2014 Elsevier Ltd.