Fixed vs Variable Electricity Rates: What Can Change?

A fixed supply price still leaves room for a bigger bill

A fixed electricity rate usually locks the supply price per kilowatt-hour for a stated term. It doesn't lock how many kilowatt-hours your home uses, and it doesn't necessarily lock the utility's delivery charges. A variable supply rate can change under the contract's pricing rules. The first price you see may apply for only one billing cycle.

This comparison is for households whose address is eligible to choose a retail electricity supplier. That choice isn't available at every US address. The examples below use Pennsylvania's retail-choice system; its disclosure and renewal rules shouldn't be treated as nationwide protections. Start with your state utility commission's shopping information and your delivery utility's service area, rather than assuming an offer covers you.

For an eligible customer, the decision is partly about what you can budget for and partly about what you're agreeing to do when the term ends. A lower starting price is useful information. It isn't the full contract.

Separate the supplier's promise from the utility's charges

Pennsylvania's official PAPowerSwitch site distinguishes the company selling electricity from the company delivering it. Choosing a supplier doesn't replace the local distribution company. On a bill, look for the generation or supply section before comparing a supplier's cents-per-kWh offer with your current price.

PPL Electric Utilities tells its Pennsylvania customers to use its Price to Compare, the default supply rate, as a shopping reference. That is a comparison for the supply portion, not a quote for the entire bill. Compare prices covering the same service and usage dates; an offer starting after a default-rate change needs the new reference price.

Even with an unchanged supply rate, higher usage means a higher supply charge. At an illustrative 12¢ per kWh, 700 kWh costs $84 for supply and 1,000 kWh costs $120. Delivery, fixed charges and any other applicable bill items come afterward. A fixed per-kWh contract is different from an offer advertising a fixed monthly payment.

Read the variable-price clause before comparing the first month

PAPowerSwitch explains that variable prices can change at intervals set by the agreement, potentially by the hour, day or month. Don't assume that every variable plan tracks a published wholesale index, or that a falling market automatically produces the same reduction on your bill. Read the factors the supplier says it uses.

Pennsylvania's disclosure rule, 52 Pa. Code § 54.5, requires a variable-price contract to explain the basis for changes, any limits on those changes and the first billing cycle's price. It also requires an explanation of when and how you'll learn about a new price, including disclosure if you won't know until billing. Those details answer a more useful question than whether a sales page calls the plan flexible: how much notice and how much exposure would you actually have?

For a Pennsylvania variable offer, request the available monthly price history for your customer class and distribution territory, up to the previous 24 months. The rule provides for that history and warns that it doesn't predict future prices. Use it to see the range of past bills, not to turn last winter's prices into a forecast.

One low month can disappear in the three-month total

Here is an invented supply-only comparison, not an available tariff or a prediction. Both plans serve the same household using 800, 1,000 and 1,200 kWh over three months. Plan A stays at 12¢ per kWh. Plan B starts at 10¢, then charges 13¢ and 16¢. Assume no supplier monthly fees, credits or cancellation charges; exclude delivery and taxes from both sides.

Weight each price by the electricity used at that price

Plan B saves $16 in the first month but costs $42 more across the three months. Its usage-weighted supply price is $402 ÷ 3,000 kWh = 13.4¢ per kWh. Simply averaging 10¢, 13¢ and 16¢ gives 13¢, which understates this household's cost because the most expensive month also has the most usage.

The result could reverse with different future prices. A fixed contract buys price certainty for the covered term; it doesn't guarantee the lowest cost. When comparing real offers, calculate each month's usage multiplied by that month's price, then add every applicable supplier fee. Keep the same consumption assumptions on both sides.

The US calculator linked below models one rate, fixed charges and separately entered taxes and fees. You can run individual monthly scenarios with known prices. It doesn't forecast variable rates or reconstruct time-of-use periods, tiers, demand charges or solar credits. Don't enter only an introductory supply rate and treat the result as the full utility bill.

A real contract shows why the end date matters

The Constellation Pennsylvania residential disclosure linked in Sources, plan ID 12926, describes an initial 12-month fixed supply contract. Its summary provides a 90-day satisfaction period and a $150 early-termination fee outside the stated fee-free periods. It also says cancellation after the second expiration notice and before the term ends carries no early-termination fee. These are terms from that document checked November 2, 2026, not a recommendation or a quote for your address.

That document says failure to respond to its notices may lead to a 12-month extension at the price in the renewal notices, with separate cancellation terms for the renewal period. A renewal therefore doesn't always mean an automatic move to a monthly variable rate. Read the actual end-of-contract provision rather than relying on a general description of fixed plans.

PAPowerSwitch's Pennsylvania guidance describes two expiration notices, the first 45–60 days before the contract ends and the second 30 days before. Read the new price, the response deadline and the available options together. An unchanged supplier name doesn't mean an unchanged deal. Other states have their own rules.

Save the disclosure, then put the renewal review on your calendar

Before enrolling, save the exact offer and disclosure statement. Mark the initial price and its duration, any separate monthly charge, the service start date, the term length and the renewal provision. For a variable offer, record the pricing factors, change limits and notification method. For either plan, identify the cancellation charge and the circumstances in which it is waived.

Ask the supplier to resolve any mismatch between the sales page and those documents in writing. If a fee applies, compare it with the dollar difference you expect over the remaining term using your own consumption. A 1¢-per-kWh difference is $10 on a 1,000-kWh month, so a cancellation fee can outweigh a small price difference for months.

Keep the confirmation with your bill and set a reminder before the contract's renewal notices are due. When the notice arrives, compare the renewal offer with the default supply option and other eligible offers for the same service period. The number to carry forward is the next contract's price and terms, not the introductory price that first caught your attention.