The key lessons learnt reported by modellers who benefited from the support of the Commission to attend the IEW can be clustered in different groups:

1. There is a need to nurture more cooperation among modelling institutions and support access to modelling tools to a wider group of countries, more specifically:
   • Collaboration between modelling institutions is key in advancing data and modelling, and in making the tools and data available more widely.
   • Workshop such as the IEW are beneficial for Small Island Developing States (SIDSs) as they provide opportunities to get exposed to different modelling tools and create research networks. Researchers from SIDS countries should be given more opportunities to attend.
   • Countries vary tremendously in terms of the availability of data and modelling capacity in the field of energy. For example, there is very little emphasis on gathering data and modelling energy demand in Africa, and very often the continent is modelled as a single entity despite widely varying energy demand across countries. As licensed models and data prevent access and use, there needs to be a move towards open source models. This would encourage and advance collaborative model development and transparency.
2. The movement towards more integrated models able to better capture interdependencies between policy areas should be further supported as it is key to achieve a successful and just low carbon transition. Specific messages include:
   • It is important to deal with energy poverty in the context of development and climate change. Energy demand is likely to continue to increase, especially in developing countries. Therefore, advanced decarbonization technologies should be more affordable so that sustainable poverty eradication strategies can be encouraged in developing countries.
   • It is important to integrate research on energy systems with research on other systems (e.g. infrastructure needs, pollution, health care). Thinking in terms of systems and how these systems interact will enhance existing research programs and open up new research avenues. There has already been a lot of effort to link energy systems models with other systems models (e.g. transport, economic models), but this type of collaboration needs to be encouraged further and the models and data should be available as open source.
   • Future 1.5ºC and 2ºC scenarios assume aggressive energy supply transformations and significant demand reduction. This has implications for human development and the ability to end poverty. For example, projections for energy use per capita in Africa are low, and it is unlikely that many countries in Africa will realise their SDGs given the persistent energy poverty.
3. Other key lessons learnt include:
   • Even though the outputs and estimates of energy models vary widely, they all show that the transition is possible within the specified timeframe. Storage, temporal resolution and spatial resolution are the three key components for achieving the energy transition.
   • Hydrogen is a key technology in the field of long-term storage and transport. The level of deployment of hydrogen will depend on how its cost develops in the future. At the moment, there is little consistency in modelling hydrogen cost and use and as a result the estimates vary tremendously.