If the Grid Went Dark, What Fails First?

In a blackout, everything stops at once. Right? Not even close. Hidden countdowns start all over town. Which dies first: the traffic light, the cell tower, or the tap? And once a whole grid is dead, what do you start it with? Along the way: why solar homes go dark in full sun, how roughly 1,500 MW of data centers dropped off the grid almost at once, and why restarting a grid takes... power. Then the real test: April 28, 2025, when all of mainland Spain and Portugal went dark. This is an illustrative scenario: the city is not a real place, but its numbers and events come from the sources below. Real systems differ by city, utility and state. Previous in the series: If a City's Water Stopped, What Fails First?    • If a City's Water Stopped, What Fails First?   Which countdown would you want to last the longest? Tell us in the comments. Chapters 0:00 Does everything stop at once in a blackout? 0:41 Who runs out first: hospitals, signals, towers or fridges? 2:00 So which dies first: the light, the tower or the tap? 2:29 Why does rooftop solar go dark in full sun? 2:57 What if the customers vanish instead of the power? 3:39 Why does restarting a grid take power? 4:24 How did Spain and Portugal come back from zero? 5:44 Most outages are local: who gets power back first? Real photos and footage: public domain / CC0 / CC BY / CC BY-SA, credited below. Credits (CC BY / CC BY-SA; images cropped or resized, a passer-by's face blurred in the Pamplona photo): • USA, 2013 · "Battery backups for a traffic controller system" by Z22 · CC BY-SA 3.0 · https://commons.wikimedia.org/wiki/Fi... • Amersfoort, Netherlands, 2008 · "Solar panels on housing in the Netherlands" by Eneco Group · CC BY 2.0 · https://commons.wikimedia.org/wiki/Fi... • Auckland, New Zealand, 2018 · Forest355 · CC BY-SA 4.0 · https://commons.wikimedia.org/wiki/Fi... • Ashburn, Virginia, 2020 · Vahurzpu · CC BY-SA 4.0 · https://commons.wikimedia.org/wiki/Fi... • Rhea County, Tennessee, 2015 · David Ratledge · CC BY 4.0 · https://commons.wikimedia.org/wiki/Fi... • Pamplona, Spain, 2025 · Asier Azpilikueta · CC BY-SA 4.0 · https://commons.wikimedia.org/wiki/Fi... • Heisdorf, Luxembourg · Philippe HURLIN · CC BY-SA 4.0 · https://commons.wikimedia.org/wiki/Fi... Licenses: CC BY 2.0 https://creativecommons.org/licenses/... · CC BY 4.0 https://creativecommons.org/licenses/... · CC BY-SA 3.0 https://creativecommons.org/licenses/... · CC BY-SA 4.0 https://creativecommons.org/licenses/... U.S. public domain: USACE (P. Bloodgood, D. Barnes, M. Sauret, M. Maddox, J. Day, S. Bennett, Capt. R. Hignight, Savannah District) · FEMA (B. Koplitz, M. Nauman, E. Hernandez) · U.S. Navy (MC2 C. Croom) · USMC (LCpl D. Hess) · USAF (A1C F. Harris, SrA J. Hancock) · U.S. Army (S. Rhodes, J. Switzer) · DOE · EPA (E. Vance) · TVA · NOAA/CSU-CIRA · NASA Earth Observatory (L. Dauphin; Black Marble data R. Shrestha, NASA GSFC). CC0: Feliperpv, Chaotic Enby, Lojwe, Nvss132, DronePhotographer, QuantumDrip, Wikideas1, Theodore Christopher. Full credit list with places, dates and links: pinned comment. Sources: TxDOT, UPS/BBU for traffic signals; California Vehicle Code 21800; Texas Transportation Code 544.007; Florida Statutes 316.1235; FCC letter to Rep. Griffith (Jan 16, 2025); FCC DIRS Hurricane Helene status report (Sep 28, 2024); CDC, Protect Yourself During a Power Outage; Ready.gov, Power Outages; EPA Power Resilience Guide (2023); NYC Health, drinking water tanks; CMS-2786R (K918); CMS Appendix Z (E0041); Otis, elevator safety in natural disasters; NREL, Kroposki (2016); IEEE 1547-2018; DOE, Solar and Resilience Basics; DOE, The Road to Resilience with Rooftop Solar (2020); DOE, Inverters and Grid Services Basics; DOE, microgrids and black start; PNNL-32773 (2022); NERC EOP-005-3; NERC Incident Review (Jan 2025); PJM Inside Lines (Aug 11, 2026); ENTSO-E Expert Panel Final Report (Mar 20, 2026); EIA Today in Energy (Dec 1, 2025); DOE Quadrennial Energy Review 2017, Chapter IV; DOE, Restoring Power After a Storm (2018). UnderTown. Your city runs on things you never see. The appearance of U.S. Department of War (DoW) visual information does not imply or constitute DoW endorsement. #powergrid #blackout #engineering