Retrofitting solar panels onto existing structures may lead to performance inefficiencies that can undermine expected energy output. alysis was performed in three climate zones with varying insulation levels and solar reflectances for roofs and exterior walls. 10 and an exterior wall solar reflectance value of 0. To reduce the carbon emissions of existing residential buildings while pursuing maximum cost benefits, a multi-optimization design method for the existing residential building rooftops, retrofitted by attaching the solar photovoltaic panels and thermal collectors, was proposed in the study. It provides perks beyond just monthly savings, though. They may require extensive preparation work, however, including structural assessments and electrical upgrades that can extend the project timeline. EMS retrofitting is the process of upgrading or connecting existing energy assets – such as solar panels, EV chargers, batteries or heat pumps – to a modern energy management system (EMS).