A high temporal precision model was developed to assess the performance of thermal load following micro-CHP system design variants in detail for a number of design days. Carbon savings (relative to a base-case energy system) and prime mover lifetime drivers (thermal cycling and operating duration) were quantified. Novel performance metrics were defined, including Potential Thermal Supply Demand Ratio, and Effective Carbon Intensity of μCHP-Generated Electricity. Significant relative carbon savings were found for design variants with a PTSDR between 0.1-1.5, suggesting that it is a design selection parameter for thermal supply/demand matching. Alternative μCHP operating regimes, restricted seasonal operation, changing thermal demand, fuel and electricity grid carbon intensities, and energy storage (using batteries and hydrogen) were studied. It was found that annual relative carbon savings in excess of 23% were achievable for appropriately-sized design variants, with relatively high electrical efficiency, once a complex control strategy is applied. The control strategy also reduces thermal cycling for the μCHP design variant (versus the Thermal Load Following operating regime), hence increasing prime mover lifetime.