What follows from it
Designed interdependence
KF6
Self-sufficiency has diminishing marginal returns
Cutting the grid connection raises capital by between a fifth and three fifths, doubles to trebles the cost of electricity, and adds nothing at all in a normal year. At a cold southern site it buys 0.12 of bad-year self-sufficiency for about $1.4 million. The research names this ‘diminishing marginal self-sufficiency’: a community should buy increments until the next one costs more than importing the shortfall it covers, and no further. All three practitioners who addressed self-sufficiency as a goal argued against it.
The proposition the evidence supports is ‘designed interdependence’ rather than independence: a community that supplies most of its own needs and keeps deliberate connections for the rest, knowing which domain it depends on, in which season, and at what cost. That is more achievable than the phrase ‘self-sufficient community’ usually implies, and it is only a design decision if someone can compute it. A connection is worth leaning on only while it holds, and the hard year decides.
The condition travels with the conclusion. Interdependence is the better proposition for as long as the systems a community leans on are dependable. This research’s own finding is that the stressed year decides the outcome, and a grid connection is a stressed-year asset whose worth depends on it holding in exactly the conditions that stress it. So autonomy is poor value against a dependable grid, not poor value as such. Where the connection is weak, absent, or expected to fail when it is most needed, the arithmetic changes.
The founder of the best-documented community argues for staying connected to town rather than being self-sufficient in isolation, and a fully electric orchard keeps its grid connection because disconnecting would forfeit export revenue worth more than the connection costs.
And what a community leans on need not be the national system. Between the single community and national infrastructure sits an intermediate scale this research did not model but its evidence keeps pointing at: communities covering one another.