Heat can be converted into electricity and conversely.
Electricity can be used to produce synthetic fuels.
Fuels can be used to produce heat and electricity, as well as operating moving machines [the latter doesn't really include nuclear].

Solar heating, solar photovoltaic and agriculture/forestry compete for land use [among themselves and with food production] and depend on latitude and weather [the number of hours of sunlight].

In the case of nuclear, with breeding/reprocessing one might not need to import any new fuel for decades.

And so on.

You can call it "resources" or "generation capacity" or something else.

If it can be argued persuasively that we're going to have to import massive quantities of oil from Saudi, gas from Russia/Algeria, coal from Russia/US/China, uranium from Australia/Canada or ethanol from Brazil, then the "energy security" argument becomes a very serious argument for demand reduction as the EU energy policy.

Those whom the Gods wish to destroy They first make mad. — Euripides