The journey of electricity

From the plant or rooftop to transmission, distribution, meter and socket.

The socket is connected to a continent

Three stages, three completely different voltage levels

No generation facility — a thermal plant, a wind turbine, a dam or a rooftop with solar panels — delivers electricity directly to a home. Between the point of generation and the point of consumption there are always three physically distinct stages. Generation produces electricity, usually at a relatively moderate voltage. Transmission raises that voltage through transformers to levels of hundreds of thousands of volts and carries it, through high-voltage lines, to large substations near consumption areas, minimizing Joule-effect losses along the way — developed in detail in this section's dedicated leaf on that phenomenon. Distribution, finally, reduces the voltage in several successive stages — regional grids, then neighborhood grids, finally each building's service connection — until it reaches a level safe for household or commercial use.

What has to be built for that chain to work

High-voltage towers, overhead or underground cables, transformers of different sizes at each voltage-reduction stage, and substations equipped with automatic protection systems require significant amounts of steel, aluminum, copper, insulating materials, dielectric cooling oils, concrete for foundations, and rights-of-way along the whole route. All that infrastructure is inspected, has nearby vegetation trimmed, is repaired and renewed continuously over decades of service life — maintenance that is rarely seen but is constant.

Burying a cable is not a cost-free option

Replacing an overhead line with an underground cable can reduce visual impact on the landscape and some vulnerability to wind or ice, but it is not a solution free of cost or land use: it requires excavation along the whole route, more complex electrical insulation than an open-air cable, more demanding thermal management — a buried cable dissipates the heat from Joule losses worse than one exposed to air —, and a notably higher installation cost. There is no option for transporting electricity completely free of territorial impact; there is a choice between different types of impact and different costs.

Electricity carries no label of origin

Once electricity from any source enters the grid, it can no longer be tracked individually: all connected plants and farms contribute to the same shared physical flow, and grid operators adjust generation and demand in real time for the whole system, not plant by plant or consumer by consumer. This means that talking about "100% renewable electricity at my socket" is, in the strict physical sense, a contractual and accounting simplification — based on certificates of origin — rather than a description of which specific electrons reach a given home at any instant.

Why the electricity bill includes much more than generating electricity

The price any consumer pays for electricity does not reflect only the cost of generating it: it also includes the cost of transmitting and distributing it, the reserve capacity the system keeps available, the operation and maintenance of the whole grid, technical losses along the way, and in many countries, sector-specific regulatory charges or taxes. That structure varies considerably from country to country, which is why comparing electricity prices between countries using only each primary source's generation cost almost always gives an incomplete picture.

Reaching the grid is part of the generation project

An excellent energy source — steady wind, abundant sun, an ideal water drop — located far from consumption centers is useless without an adequate connection to the transmission grid. Evaluating any new generation project requires including, from the start, the cost and construction timeline of its connection lines, the necessary substations, the future maintenance of that added infrastructure, and social acceptance of the chosen route — not just the generation technology itself. And at the other end of the chain, saving electricity in a specific home not only avoids generating that energy at the source: it also avoids a share of the transmission and distribution losses it would have suffered along the way.

Connecting costs as much as generating

In favor of evaluating generation and connection together: a plant or renewable farm without an adequate connection line delivers no usable electricity to anyone; including the connection cost from the very start avoids apparently cheap projects that turn out much more expensive once the necessary infrastructure to reach the grid is added.

To watch: burying cables reduces visual impact but not the cost or the land needed; an overhead line is cheaper and easier to inspect and repair, but more visible and somewhat more vulnerable to extreme weather. Neither option is free in terms of land or cost.

The mistake of comparing electricity price while ignoring the grid: when two generation sources are compared only by their production price, without including the connection line's cost, transmission maintenance, or associated losses, the comparison is incomplete and can systematically favor projects located far from demand over closer ones, even if their generation is somewhat more expensive.

Before talking about "100% renewable electricity" in a contract or a label: understand that, physically, the grid mixes all connected electricity into a common flow; the label is usually based on accounting certificates of origin, not on the exact physical origin of the electrons reaching a specific socket at a given instant.

The numbers, with their source

Seven hundred kilometers of cable under the sea

The North Sea Link, operating since 2021 between Norway and the UK, is a 720 km-long high-voltage direct current (HVDC) submarine cable, with a capacity of 1,400 MW and a voltage of ±515 kV — it was, when it launched, the world's longest subsea interconnector. In 2023 it was overtaken by the Viking Link, between the UK and Denmark, at 765 km total length (650 km subsea). These projects illustrate at real scale why very-long-distance underwater electricity transport uses direct current instead of alternating current: an AC submarine cable of that length would generate parasitic reactive currents — from the cable's own capacitance surrounded by salt water — that would drastically limit usable transportable power beyond a few tens of kilometers.

Sources: Wikipedia — North Sea Link; Wikipedia — Viking Link.

Why these projects exist: sharing resources between regions

An interconnection of this scale allows a country with a hydropower surplus at a given moment — Norway, for example, with its reservoirs — to export electricity to a country with more demand or less renewable generation available at that instant, and vice versa when the situation reverses. That ability to share resources between regions reduces the amount of backup generation capacity each country would need to build separately — the same principle developed in this section's generation-demand balance leaf, applied at international scale instead of within a single national grid.

What this table is missing

These figures describe the infrastructure's capacity and length, not its total economic cost nor how long it took to obtain all the environmental and seabed-use permits needed — at this scale, permitting can take years and be as decisive for the final schedule as the physical construction of the cable itself.

Sources