This paper analyzes a simple microeconomic model of electricity market equilibrium. The parameter that shifts the demand between different points of time appears as an additive term. The equilibrium analysis can then be conveniently focused on the relation between two quantities, namely the electricity supply from intermittent sources and the subsistence level of electricity use. Our model is able to mimic the common empirical finding that a higher penetration of variable renewable electricity leads to a lower value factor for this type of power sources.