How the electrical grid is like the road network

Via US Department of Energy, CC licensed

They both have different “functional classes”.  Roads are typically classified as local, state-aid, county highways, state highways and federal highways (loosely).  Electrical systems are generally separated into the distribution network (poles to your house) and the power transmission network (power plants to substations).  Unlike roads, transmission and distribution systems are typically not owned by government in the U.S. (but are heavily regulated).  Some utilities own both transmission and distribution components (and sometimes generation).

As David points out, electric utilities are mostly private, natural monopolies.  Many are government-granted monopolies (as in Minnesota where the PUC determines service territories).  Roads are also monopolies of a sort – government is the sole provider of the service.  As a result (as David also points out) risk-taking is low but service levels are generally high (power is almost always on, roads are almost always passable) and prices determined through regulation.

Electricity retail sales via EIA

Electricity retail sales via EIA

Both roads and grids face something of an existential crisis, although perhaps to varying degrees.  Total electric power sales in the U.S. peaked in 2007, about the same time as vehicle miles traveled peaked in many parts of the developed world.  Declining VMT plus a reluctance to raise gas taxes means many jurisdictions face funding dilemmas even for maintenance of roads we’ve already built.  Fixed costs for maintenance and sunk costs looking for a return on investment create threats if past trends of continued growth were used to justify new investments.

New technologies could also plague/benefit both systems.  Electric vehicles mean gas tax revenues may eventually fall further/go away altogether and self-driving cars and other trends mean that VMT and car ownership could continue to decline.  Increasing amounts of distributed generation of electricity means utilities face fundamental challenges to their business model.

Both systems are generally highly regulated, and decisions about significant changes could be slow and incremental.  There are both good and bad impacts here.

Both systems face significant portions of policy makers and the public trying to internalize externalities that both systems have historically not had to address.  These efforts and opinions on these externalities vary by location.  Air pollution and land use pattern impacts in the case of roads, and mostly air pollution in many forms in the case of the electrical grid (but also land use impacts: mining, groundwater contamination, etc).

In both systems, we’ve prioritized equal access for all over the most efficient delivery, which might exclude some potential users.  At our highest levels of government, we’ve prioritized and subsidized a massive expansion of both.  This has both good and bad effects.

The flow of things (cars, electrons) through both is controlled in giant rooms filled with computer screens and engineers.

They both can kill you very quickly if used improperly.

How the grid is not like the road system

I can make my own electricity, and in most places I can send it to the power grid, but very rarely are you allowed to build your own road that serves any significant purpose.  Functionally, you can’t build your own car, either (although, you can make a bike).

Absent any maintenance, most roads would last quite a long time without anyone touching them, and in most places usage of the network would still be feasible, even without modern traffic control.  The grid on the other hand, takes constant monitoring and adjusting to make your lights turn on when you think they should, and really wouldn’t operate without constant human (and computer) oversight.

The costs of the electrical grid, as far as I can tell, are more directly born by the user.  If a utility wants to upgrade something, they submit a request to the PUC who authorizes the cost to be borne by rate-payers.  Road costs (including transit and other user costs) can be distributed over a wide variety of sources, public and private.  (I may be off the mark here, so fill me in if necessary).

The flow of things in the electrical grid has been historically one-way: from generator to consumer through a tree-like network (this is changing).  Transportation networks are generally more spider webby, with flows in many directions at once.

One squirrel or tree branch can shut down huge portions of the electrical grid, but small mammals generally cannot shut down roads.

One is generally overhead, the other is generally underfoot.

Roads have a lot more songs written about them.


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2 Responses to How the electrical grid is like the road network

  1. Bill Lindeke
    Bill Lindeke September 5, 2013 at 11:28 pm #

    that last point is great.

  2. Walker Angell
    Walker Angell September 6, 2013 at 4:37 pm #

    Interesting analogies. When I designed data/voice xmission networks we often compared what we did to traffic engineering, never thought about the grid comparison.

    I’ve looked in to the funding a couple of times. It’s quite convoluted. As best I could tell funding for road construction and maintenance was about 50% from user fees (sales, registration, gas, and wheelage taxes, and tolls) and 50% from general funds. Surface roads a bit more from general funds, approaching 70% in some counties, and interstate highways a bit less. One problem was how often sub projects, like sound barriers, landscaping, sewer, or even land acquisition, were funded from general funds but completely separate from the road project so the amount funded by general funds may be a bit more.

    As you pointed out though, we’re not even keeping up with maintenance, so we’ll need to come up with more funding for transportation in the future. I don’t have a problem with a road being funded from general funds if the road is designed to serve the general taxpayer and not just drivers. A well-designed complete street that includes a safe cycle-track or path and a welcoming pedestrian-way serves everyone and thus should be mostly paid for by everyone. In this case the 50/50 split of user fees and general funds is likely appropriate. Drivers will pay more (user fee plus their portion of general fund contribution), but they also require perhaps 20 to over 100 times as much in terms of land, construction, and maintenance cost.

    A road designed just to serve motor vehicle drivers should be paid for 100% from user fees since that is who it serves exclusively.