This actually is a topic near and dear to my heart. I honestly believe that with a bottom upwards, total reimplementation of our modern Western-style civilization, we could still have a reasonable facsimile of our current lifestyle, but using 15% of the present energy we use.
A brief description of the ground-up
Infrastructure changes required:Transportation: The existing interstate highway system is abandoned in favor of electric-powered high speed rail, which shares passenger and freight on the same tracks. Much of the power is generated by PV panels and wind turbines located along the rail corridors to minimize the length of the power interconnects. Many of these rail corridors are located over the old highway pavements, saving lots of money and energy for excavations. Lightweight but immensely strong and long but elegantly designed and relatively inexpensive bridges of composite materials are used. Rail hubs are co-located with the few remaining airports which remain in major urban areas. Everybody, and I mean everybody, must live within say 100 miles of a rail station (not a hub), all remaining roads are local public or private, and all private vehicles and commercial short range trucks are EVs with 100+ mile range. Provision is made to transport private EVs via rail for those that still want a "road trip" vacation. EV chargers are standardized, coin operated, and solar powered. This scheme still allows you to choose urban, small town, suburban, and rural lifestyles. Priority and government subsidies are devoted to designing new composite airliners which are powered by electric ducted-fan jets, fast and even barely subsonic.
Agriculture: Mechanized, electric farm machinery is used, greenhouses darned near everywhere extend the growing seasons, and emphasis is placed upon growing the bulk of food (say 75%) within 100 miles of where it gets consumed. The remaining 25% is exotic, imported foodstuffs from hundreds of miles away. There are exceptions - sugar cane for example should only be grown in the Tropics, and sugar beets in warmer Southern Temperate zones. Grain production is most efficient in the MidWest and Western states, and bulk grain would be shipped via the electric trains. Much of the current seafood consumption is replaced with farmed freshwater fish, and chickens already grow everywhere from the Tropics to the Arctic - but beef and pork are exotic foodstuffs in the 25% category, because of the energy expense of feeding grains to animals. Envision large urban areas surrounded by greenhouses, poultry ranches, and farmed fish ponds - largely organic and healthful foods which do not require the selective breeding for shelf life because they are consumed within two days of harvest. Yes, you may have to adjust to having bananas and other fruits as seasonal crops only - unless you would pay the premium for greenhouse crops in the off season.
Residences: All existing homes, aside from a few hundred which already display extreme energy efficiency, get either retrofitted to the new energy standards, or torn down and replaced, depending upon which is more economical. North of the Mason-Dixon line, the energy standard is the existing PassivHaus standard, which originated in Europe. South of the Mason-Dixon line, the standard is LEED Platinum. There must be 100% compliance with this requirement, aside from a limited number of historic structures which are used as Museums, not residences. The standard for workmanship is a 100 year structure lifetime, with easily upgraded and standardized mechanical systems. There are required standards for recycled material content and a contractor must demonstrate compliance with design, demolition, and construction phases. The government assists homeowners to remove/rebuild or to retrofit an existing structure to the same energy standard, which is </= 10% of present average energy consumption. (This is a huge task but completely possible, the 10% energy consumption standard is easily met with today's construction methods and materials.)
Workspaces: Government and business spaces and factory floors all need redesign and renewal or retrofit to the same goal as private residences, which is 10% of current energy consumption. This is a complex topic due to the sheer range of buildings being renewed - but note that covering the roof of a structure with solar PV, and surrounding it with wind turbines, also count as part of the 10% of current energy consumption - recall the Tesla GigaFactory, or the modern campus Apple is now building on the site of my former HP workplace in Cupertino.
Power Grid: DC high voltage main grid interconnects are built at the same time and in the same places as the high speed rail service above. Rural residences and farms are designed for "off grid" living, which is very easily done when the residence or farm consumes 10% of the current energy. This allows us to abandon over 1/3rd of the power grid, the most costly final 10 miles between main power feeds and individual consumers.
Net/Net: When we have reached the 15% of current consumption goal, the bulk of our energy can easily be supplied with renewables, and the remaining FF supplies will last for centuries. You will no longer see this looking down from space:
....because any remaining outside lighting is directional and supplied by efficient LED light sources.
My estimation of what is required for this infrastructure renewal is 25+ years and 25% of our GNP for that same period. This amounts to an entire generation of hardship for Americans - but with full employment and a necessary redistribution of population, allowing everyone the lifestyle they desire in the place they desire.
How we pay for this and more importantly, how we get the tax revenues, or stimulate the up-front business environment to do these things with private enterprise - those are interesting topics, but a separate conversation. The short version would be, we need political leadership of the quality of George Washington, Abraham Lincoln, or Franklin D Roosevelt. This seems unlikely in the present political environment.