**4. Discussion and Conclusions**

This project of street lighting systems reveals two important issues:


Fossil Energy-saving systems (e.g., insulation, heat pumps, windmills, PV cells), have the characteristic that the TCO is less than the investment costs. In the EVR charts, this is characterised by a line with a negative slope, since there are savings in eco-costs as well as costs (see Figure 14). These savings are developing over time. After the pay-back period of the system, the extra cost savings will have a rebound effect [49], since these savings will result in other expenditures (e.g., on cars or holidays). When the EVR of such an expenditure is more than the EVR of the savings, the net result is negative for the environment. When the EVR of the expenditure is less than the EVR of the savings, the net result for the environment is positive [49]. The net result of energy savings has, therefore, a behaviour aspect.

Products for consumer markets must have a surplus value at the moment of purchase, whereas in cases of non-profit organisations, the non-profit organisation has an intermediate position between the stakeholders that pay for the project, and the stakeholders that benefit from the project. As a consequence, eco-efficient value creation for non-profit organisations like a municipality, has two distinct project phases: (1) the choice of the system concept, and the trade-offs between the value (in this case the CPV of the citizens), the eco-burden, and the costs (TCO), are done prior to the start of the implementation project, leading to a budgetary TCO limit. (2) after the project approval, this TCO limit will restrict the further design freedom, however, the approach of eco-efficient value creation still continues for designing further details: creating maximum value at minimum eco-costs. The same situation exists for big infrastructural projects and building design.

The design of a new concept of domestic street lighting system for the city of Rotterdam is a practical example of the approach of Eco-efficient Value Creation. The new concept results in a considerable reduction of carbon footprint and eco-costs, shows the benefits for the municipality and for the residents, and results in a viable business case. The end-result might seem logical and obvious, as it is the case for many good innovations. For all parties that were involved in the design, however, it was clear that such an achievement was the result of the well-structured design process in combination with the establishment of the CPV and eco-costs for several design alternatives in the early design stages (see Supplementary Materials). The design project won the Future Ideas Thesis Competition.

**Supplementary Materials:** https://www.ecocostsvalue.com/EVR/img/references%20ecocosts/Nine%20Klaassen% 20Report.pdf and https://www.ecocostsvalue.com/EVR/img/references%20ecocosts/Nine%20Klaassen% 20Appendices.pdf.

**Author Contributions:** Conceptualisation, N.K., B.F., A.S.; methodology, B.F., A.S.; writing—original draft preparation, N.K.; writing—review and editing, J.V.; All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Conflicts of Interest:** The authors declare no conflict of interest.
