The combined-heat-and-power (CHP) plants play a central role in many heat-intensive energy systems, contributing for example about 10% electricity and 70% district heat in Sweden. This paper considers a proposed system integrating a high-temperature thermal storage into a biomass-fueled CHP plant. The potential and benefits for the individual CHP plant, as well as for the electric grid at large-scale implementation, are studied. The original and integrated systems have been compared by energy and exergy analysis, the results indicating only minor differences. Individual CHP companies can benefit from saving fuel and become more flexible towards customer demands. The integrated system can contribute to new storage capacity in the national electric grid, valuable as the share of variable renewable electricity increases, such as wind and solar power. In a reasonable future scenario with a broad implementation of the integrated system, 53% of electricity that would otherwise be curtailed, could be absorbed and used. At the same time it will be able to replace about 21% of the fuel in the CHP plants. This can help to phase out nuclear power towards the goal of “100% renewable electricity”.