Energy Recovery Ventilator (ERV) is one of the efficient ways to reduce fresh air load. However, there is a major concern, which energy recovery cannot trade off ERV's fan power consumption, even with causing counteraction to precool (preheat) fresh air in winter (summer). In this study, energy recovery is quantitatively evaluated during cooling season and heating seasons for an office building in Chongqing by employing TRNSYS. Based on the ERV's fan power consumption and energy saving which is converted to chiller's electricity consumption, outdoor fresh air is divided into four zones (zone I, zone II, zone III and zone IV) on a psychometric chart (ID chart). The results show that ERV which only operates in profit zones (zone III and zone IV) can increase electricity saving by 65.23% and reduce operating time by 31.18% than that operating throughout heating and cooling seasons. The proposed operation condition zones method can help identify profit pattern, minimize the energy consumption of ERV and air conditioning system. (C) 2015 Elsevier B.V. All rights reserved.