When you flip a light switch, cozy up next to a space heater or turn on your electric stove to prepare dinner, electricity flows instantly. But behind that simple action is a modern engineering marvel, the power grid, which consists of millions of miles of power lines.

The power grid is a vast network that generates, moves and manages electricity so it’s available whenever you need it. While most of us don’t think about it day to day, understanding a few basics can help you appreciate just how important this invisible system really is to daily life.

In this month’s blog, we look at three things you should know about the power grid:

1. Electricity has to be generated before you use it.

Unlike water in a tank, electricity traditionally hasn’t been stored in large amounts (though this is changing somewhat today). This means that most of the power you use is being generated by a power plant and distributed to your home not long before you flip that switch.

Electricity comes from many different sources – fossil fuels, renewable sources, nuclear, etc. – but unless it’s stored in batteries, a pumped-hydro facility or other new storage technologies, it must be generated to match usage. This is a delicate balancing act that we’ll explore later.

2. The grid is a giant delivery system.

Once electricity is generated, it has to travel – sometimes hundreds of miles from a central power plant – to reach your home. This happens through a complex network of millions of miles of power lines and equipment that work a lot like highways for electricity.

High-voltage transmission lines carry electricity long distances from power plants. Substations then lower the voltage so it can safely move into neighborhoods, and distribution lines are the smaller wires you see on poles that bring electricity directly to your house.

This delivery system has to be carefully maintained. Storms, accidents or equipment failures can interrupt the flow of electricity, which is why utility crews work quickly to restore power when outages happen and why new technologies are being added to improve the grid.

3. Grid operators keep everything in balance.

Here’s something that many people don’t know: the amount of electricity being generated must always match the amount being used – down to the second. If supply and demand fall out of balance, the grid can become unstable and even shut down (i.e., blackouts).

That’s where grid operators come in. These are highly trained professionals who monitor the system 24/7. They use advanced tools to predict how much electricity people will need and make sure enough power plants are running to meet that demand. They also adjust when unexpected things happen, like a sudden heat wave that causes millions of air conditioners to turn on at once.

Plus, grid operators typically will maintain a reserve margin, which is “a specified amount of backup electricity generating capacity that is available to compensate for potential forecasting errors or unexpected power plant shutdowns.”

The power grid is one of the most important systems in our daily lives. It keeps our homes comfortable, our devices charged and our communities running. By understanding how electricity is safely and efficiently generated and delivered, you gain a new appreciation for the massive machine that powers modern life. The next time you flip a switch, remember that there’s a whole world of technology and teamwork behind that simple spark of light.