The United Nations Brundland Commission popularized the term “sustainability” in 1987 and defined it as “meeting the needs of the present without compromising the ability of future generations to meet their own needs”. Too often this definition has been simplified in the energy field to imply that energy obtained from inexhaustible resources is de facto sustainable energy. Hence, renewable energy has become an equivalent to sustainable energy, but also nuclear is branded as such given the tiny amounts of the superabundant isotopes required to produce energy for as long as human civilization would need it.

Yet, the sustainable concept is far more restrictive than either inexhaustible or renewable. The question one must ask is whether any limitless form of energy leaves future generations’ ability to meet their own needs intact. The answer usually concentrates on establishing the ability of future generations to meet their needs for energy (or energy services: heat, light, force, transport, etc.) and the immediate consequences for the environment. In that narrow sense renewables and nuclear may qualify as sustainable. But is that enough?

We hardly reflect on how past and present decisions regarding the energy system may endanger future generations’ abilities to meet their own needs. All kinds of needs, some of which we may be unable to anticipate from our present. For instance, enjoying a landscape or ploughing a fertile land may become impossible after a large hydropower dam has been built. The livelihoods of future generations will be altered forever because of the downstream effects of dams: the loss of fisheries, decreased amounts of water, and a reduction in the fertility of farmlands and forests due to the loss of natural fertilizers and irrigation in seasonal floods. Another water related example: water is seldom considered as an “energy” resource, and yet, the United States requires more freshwater for producing hydroelectricity and cooling thermoelectric plants than for any other use including agriculture! Access to freshwater may became an imperative urge for future generations, limiting not only the ability to meet their energy needs but more peremptory ones.

Past energy decisions condition future generations to meet their needs when past choices impose a cost payable in the future. Let it be the recycling of defunct solar panels or the building and supervision of permanent storage for nuclear spend fuel for centuries to come. Moreover, energy infrastructure tends to indebt several generations since the capital costs repayment schedules expand over decades. They impose a sort of intergenerational opportunity cost on future generations: since coming generations will have to pay past debts they will have to forgo part of their consumption and investment opportunities, which may compromise their ability to meet their own needs.

The weight that past choices have in limiting present and future decision making regarding energy seems large. Energy systems are subject to strong and long-lived path dependence, due to technological, infrastructural, institutional and behavioural lock-ins. Thus, for building a truly sustainable energy system, we shall be aware of the implications that our current choices will have for future generations. Analysing historical energy choices and whether they jeopardized our ability to meet our present needs, may help to shed some light determining the way forward.

M. d. Mar Rubio-Varas, editor of The Economic History of Nuclear Energy in Spain, is Associate Professor in the Department of Economics at the Public University of Navarre, Spain.