I paid my electricity bill without reading it for two years. Then my bill jumped forty dollars in one month and I actually looked at the breakdown. There was a “delivery charge” that cost more than the electricity itself. I had been paying it every month without knowing it existed.

Here is how to read your bill and spot the charges you can do something about.

The two-part bill most people do not understand

Your electricity bill has two main charges: supply (the actual electricity you used) and delivery (the cost of getting it to your house through power lines). In many states, supply is measured in kilowatt-hours — that is the part you can control by using less electricity. Delivery is often a fixed charge plus a per-kWh fee that you cannot avoid.

On my bill, delivery was higher than supply. I was using $45 worth of electricity and paying $52 to have it delivered. The total was $97, but only $45 of it was within my control.

What each line item means

Customer charge: A fixed monthly fee just for being connected to the grid. Usually $5 to $15. You cannot reduce this.

Distribution charge: Pays for local power lines, transformers, and meters. This is usually per kWh, so using less electricity reduces it.

Transmission charge: Pays for long-distance high-voltage lines. Also per kWh. Reducing usage helps here too.

Generation / supply charge: The actual electricity. This is the main number you can control by using less power.

Taxes and surcharges: State and local taxes, plus sometimes things like renewable energy surcharges or low-income assistance fees. Fixed costs you cannot change.

How to actually lower your bill

Since delivery charges are mostly per kWh, every kilowatt-hour you save reduces both your supply and delivery costs. A kilowatt-hour saved is worth more than just the supply rate.

The biggest home electricity users: air conditioning, electric heat, water heaters, clothes dryers, and refrigerators. Target the big ones first. Setting your AC two degrees higher saves about ten percent on cooling costs. Washing clothes in cold water eliminates the water heater cost for laundry. Running the dryer one less load a week adds up over a year.

Also check if your utility offers time-of-use rates. Electricity is cheaper at night in many areas. Running the dishwasher and doing laundry after 9 PM can cut those costs by a third or more.

Check for errors

Look at your meter reading on the bill. Compare it to the reading on your actual meter. Utilities sometimes estimate usage when they cannot access the meter. You could be paying for electricity you did not use. If the estimated reading seems too high, call the utility and request an actual reading.

I cannot get rid of the delivery charge, but knowing about it changed how I think about saving electricity. Every watt saved counts double now.