## 4 Cost of Energy Results and Discussion
### Cost of Energy for Households (Without Taxes and Levie)  
Total system costs or system levelized energy costs do not represent the combined effect of energy-saving measures, higher efficiencies, and decreased costs. Therefore, the cost of energy for an average household CoE\({}_{\text{hh}}\) (\(\upxi\)/hh/year) is introduced as an example. To put the designed system intoperspective, a comparison with today's household energy costs would be interesting to make. This, however, is not as straightforward as it seems.  
The developed system and the technologies used are very different from today's fossil-based energy and transportation system. Cities today are not self-sufficient: They import energy from both the national and the international power and fuel network. These national and international electricity and fuel supply chain networks also come at a cost. This, however, falls outside the scope of this study.  
The analyzed size of this system is very small; one could compare it to a neighborhood within these big urban areas or a very small village. In addition, only the building and the road transportation sector are analyzed and integrated here. Increasing the system size and combining several different sectors would create more integration opportunities and reduce costs. For example, the equipment could be shared to avoid underutilization.  
Environmental and health savings and welfare creation (e.g., jobs) [143] compared to the present fossil system are difficult to express in costs for this specific and small-scale system. In the present situation, taxes and levies on energy can represent a great part of the energy costs for household consumers, but future estimates of taxes and levies are not within the scope of this study.  
Summarizing, it is very difficult to make a fair cost comparison. Nevertheless, a very simple energy cost comparison for an average household is shown below, without any taxes or levies. The present fossil situation is compared with the designed 100% renewable system in the Near Future and the Mid Century scenarios. Additional background data for the present situation can be found in Appendix F.  
The cost of energy for a single household CoE\({}_{\text{hh}}\) (\(\ell\)/hh/year) consists of the cost of energy for the building energy CoE\({}_{\text{hh,B}}\) (\(\ell\)/hh/year) and the transportation energy CoE\({}_{\text{hh,T}}\) (\(\ell\)/hh/year); see Table 5. The Near Future scenario CoE\({}_{\text{hh}}\) shows an increase compared to the present situation, although not by several magnitudes. For Murcia, the increase is only 30% in the Near Future scenario. This shows that even though new hydrogen technologies are used, Near Future scenario costs can come close to the present situation costs and thus give reason to explore further. We should bear in mind that the Near Future scenario only changes technologies (e.g., electric water heating and heat pumps for heating) and has no significant energy savings as in the Mid Century scenario. However, in reality, the installation of a heat pump often goes hand in hand with energy-saving measures like insulation. What's more, any further integration with other sectors and increasing the system size could also further reduce costs.  
The cost of energy for households (without taxes and levies) in the Mid Century scenario is significantly lower (up to 65%) compared to the present situation--namely 770 and 520 \(\ell\)/year per household for Hamburg and Murcia, respectively.  
Therefore, the designed system is not only renewable and reliable but also affordable.