The warming of the Earth continues with unprecedented speed and the global mean average temperature over the last 3 years exceeded 1.5 Celsius compared to pre-industrial value indicating the urgency to improve understanding of the risks and consequences related to the ongoing climate change. To do so and to project the future climate evolution Earth System Models (ESMs) are a central tool. ECE-HR is linked to the EU-Horizon project OptimESM that is coordinated by SMHI. The goal of OptimESM is to better describe and understand the Earth system (including e.g. interactive vegetation, the carbon cycle, polar ice sheets) and its response to changes in greenhouse gas forcing and land-use. To reach this goal, OptimESM aims to increase the resolution of ESMs to more reliably represent key physical climate processes, climate variability and regional climate change including extreme events. As part of the EU-project OptimESM, SMHI has already made steps towards a new, high-resolution-version of EC-Earth, EC-Earth4-HR. This model version will be applied in ECE-HR to run control, historical and future simulations following the protocol of the High Resolution Model Intercomparison Project (HighResMIP). Thus, ECE-HR is contributing to answer the main research questions that HighResMIP is addressing, e.g. can high-resolution help to reduce key structural uncertainties of future climate projections and can it improve the representation of future weather extremes and pattern effect, but allows also to investigate the relative importance of better representing Earth system processes versus increasing the resolution. Thus ultimately, contributing to the question, what is the optimal distribution of computing resources between model complexity and model resolution for a variety of different climate processes.