This paper compares various flexibility options to support renewable energy integration across the energy transition using energy system modelling. We analyse new flexibility assets such as electricity storage, heat pumps, demand-side response with existing wet appliances, electric boilers for domestic hot water and distribution grid expansion, along with energy efficiency measures in electrical appliances and building retrofitting. We propose an open-source sector coupling model (GRIMSEL-FLEX) to minimise, from a social planner perspective, the total cost of the energy system for electricity and residential heating supply in Switzerland, including various types of consumers and urban settings. We find relevant feedback mechanisms among various flexibility options. Firstly, electric boilers have a larger flexibility potential than demand-side response with wet appliances since they reduce storage investments by more than 26% by 2050 (only 12% for demand-side response). Secondly, 34% more electricity storage is needed if heat pumps replace all fossil-based heating and 80% to replace all heating systems entirely. Thirdly, we find a shift in the operation of heat pumps, electric boilers and wet appliances from night to midday, resulting in larger photovoltaic deployment (22%-66% for the residential sector). Finally, electricity storage capacity induced by heat pump deployment is highly dependent on the retrofitting rate. With 1% per annum, 86% of storage investments can be avoided and it can be counterbalanced with a high retrofitting rate of 2% per annum.