How the US Power Grid Works: A Plain Guide (2026)

A family in Allentown turns on a window AC unit on a July afternoon. Somewhere in western Pennsylvania, a natural gas turbine spins a little faster. The adjustment happens in under a second, coordinated across hundreds of miles of wire by computers and grid operators who never sleep.

That invisible choreography is the US power grid, and most Americans never think about it until the lights go out. But understanding the basics pays off, especially in a state like Pennsylvania where you can legally choose who generates your electricity and what you pay for it.

The phrase 'the US power grid' is a small simplification. There are actually three main interconnections operating largely independently of one another.

The Eastern Interconnection covers roughly everything east of the Rockies, including Pennsylvania. The Western Interconnection covers the western states. ERCOT covers most of Texas as its own island. These three regions exchange very little power with each other because the connections between them are limited and expensive to build.

Within the Eastern Interconnection, smaller regional grid operators manage the day-to-day balancing act. Pennsylvania falls almost entirely within the territory of PJM Interconnection, a regional transmission organization that coordinates power across 13 states and the District of Columbia. PJM runs a wholesale electricity market, dispatches power plants in real time, and plans the transmission infrastructure that underpins every kilowatt-hour a Pennsylvania family uses.

The grid has three main layers, and each one does a distinct job.

Generation. Power plants convert some form of energy, whether natural gas, wind, nuclear, or solar, into alternating current (AC) electricity. In Pennsylvania the mix includes substantial nuclear output, natural gas, and a growing share of renewables. The electricity leaves a plant at relatively low voltage.

Transmission. Before traveling long distances, that electricity is stepped up to very high voltages, often 138,000 to 765,000 volts, by transformers at the plant. High voltage means lower current, which reduces the energy lost to heat over long wires. These high-voltage lines, the ones strung on steel towers across open countryside, form the transmission grid. PJM operates and monitors thousands of miles of these lines across its territory.

Distribution. Near your neighborhood, substations step the voltage back down, first to a medium range and then to the 120/240 volts that arrive at your meter. The local utility, PECO in the Philadelphia region, PPL Electric in the Lehigh Valley and central Pennsylvania, Duquesne Light in Pittsburgh, or FirstEnergy Pennsylvania, which does business as Met-Ed in eastern and southeastern Pennsylvania, Penelec in the north and center, West Penn Power in the southwest and south-central region, and Penn Power in the west, owns and maintains these local wires. This is the part of the grid that the Pennsylvania Public Utility Commission (PA PUC) regulates most directly.

Unlike water in a pipe, electricity cannot be stored at scale in the grid itself. Generation and consumption must match almost exactly, every second of every day. If too much power floods the system, frequency rises above the standard 60 Hz. If too little is available, frequency drops. Either extreme can damage equipment or trigger cascading outages.

PJM solves this through markets. Generators bid their available capacity and price into a day-ahead market and a real-time market. PJM's computers accept the cheapest bids first, working up the stack until supply meets forecasted demand. That process sets the wholesale price that flows, eventually, into the supply rates Pennsylvania utilities charge their default-service customers.

Pennsylvania restructured its electricity market in 1996 under the Electricity Generation Customer Choice and Competition Act. The idea was to separate the competitive parts of the business (generation and supply) from the natural-monopoly parts (wires and delivery).

Today, your utility still owns the wires and is responsible for delivering power reliably. That part of your bill, the distribution charge, is not something you can shop. But the supply portion, the cost of the actual electricity, is open to competition. You can stay on your utility's default service, or you can enroll with a licensed competitive electric generation supplier (EGS).

The benchmark that tells you whether your utility's default service is a good deal is called the Price to Compare. The PA PUC requires each utility to post its current Price to Compare so customers can make an informed decision. The state comparison tool, PAPowerSwitch, lists licensed suppliers and their current offers alongside each utility's Price to Compare.

Default supply rates vary significantly across the state as of August 2026. PECO customers in the Philadelphia area are on the lower end, at roughly 11.8 cents per kilowatt-hour. West Penn Power sits at about 12.1 cents. PPL Electric and Penelec are both around 13.1 cents. Met-Ed is near 14.0 cents, and Duquesne Light customers in the Pittsburgh area are at the high end, approximately 14.1 cents per kilowatt-hour.

The lowest competitive supplier rate currently available in Pennsylvania is approximately 10.4 cents per kilowatt-hour, though that rate varies by utility territory and changes frequently. For a household using 900 kilowatt-hours per month, the difference between the highest default rate and the lowest competitive rate amounts to a meaningful annual sum, which is exactly why the PA PUC built the shopping infrastructure in the first place.

For live, up-to-date comparisons across all utility territories, visit ElectricRates.org's Pennsylvania page or PAPowerSwitch directly.

The transmission and distribution infrastructure that keeps the lights on costs money to build, maintain, and upgrade. Those costs show up in your delivery charge, not your supply charge. When a storm knocks out lines in your area and your utility sends crews overnight to restore power, you are seeing the distribution layer of the grid at work.

PJM also runs a capacity market called the Reliability Pricing Model, where generators are paid to guarantee they will be available during peak demand periods. That capacity cost is recovered through wholesale prices and eventually embedded in the supply rates utilities charge. So the work of keeping the grid reliable in the dead of winter is already baked into your bill, whether you are on default service or a competitive supplier.

Knowing how the grid works clarifies what you actually control. You cannot change the physics of transmission or your utility's distribution charges. But you can control who sells you the electricity that travels over those wires.

Start by finding your utility on your bill and looking up its current Price to Compare, either through the utility's website or PAPowerSwitch. Then check whether any competitive supplier in your territory is offering a rate below that benchmark. Contracts vary in length, and some carry early termination fees, so read the terms before enrolling. Fixed-rate contracts lock in a price for the contract period; variable-rate contracts move with market conditions.

If you are a lower-income household, ask the PA PUC or your utility about the Customer Assistance Program (CAP), which can cap your bill as a percentage of income regardless of which supply option you choose.

The grid is vast and complex. Your decision, though, is straightforward: compare the Price to Compare to what competitive suppliers are offering, and choose accordingly. ElectricRates.org's Pennsylvania page keeps current rates in one place so you do not have to hunt across multiple sites.