The increasing number of Distributed Generation Units (DGs) in distribution grids is challenging the way electrical systems are designed and operated. For traditional power systems, Low Voltage (LV) networks play a passive role in voltage regulation, but when DGs are present the LV network may play an active role in voltage control. In this paper, a voltage control strategy using mini Combined Heat and Power (mCHP) is proposed. For this aim, the electrical and thermal dynamics of a mCHP plant are considered, a voltage controller is designed and a voltage control mode is developed, which prolongs the regulation action of the mCHP unit using heat storage. Simulations are conducted considering thermal and electrical demand of a typical multi-family house in the climate region of North Rhine-Westphalia, Germany. Aspects of resulting voltage and thermal profiles, compared to a traditional heat lead mode, are discussed for an exemplary day.