The simple model: gas as a product + a delivery service
A gas bill often looks like a math problem. But the underlying model is straightforward: you're paying for natural gas as a fueland you're paying for the system that delivers it.
If your bill has a "supply" section and a "delivery" section, that's the bill's way of separating the product (the gas) from the service (the pipes, meter, maintenance, and operations that keep gas available at your home).
This article explains those two categories in plain English and gives you a quick checklist to interpret changes. For the broader overview of gas service, start withNatural Gas Explained.
Supply (commodity) charges: what they usually include
The supply charge is the cost of the natural gas itself. It's often priced per therm. In some regions, you may be able to choose a supplier for the supply portion. In other regions, supply is bundled and provided by the same utility.
Supply rates can change based on market conditions, seasonal demand, and how utilities procure fuel. That's one reason the price per therm can look different between summer and winter.
If you're unsure how to locate the therm usage and supply price on your bill, seehow to read your gas bill.
Delivery (distribution) charges: what they usually include
The delivery charge covers the cost of getting gas to your home reliably. It often includes:
- Pipelines and distribution mains
- Local neighborhood service lines
- Meters and meter reading systems
- Maintenance, repairs, inspections, and safety programs
- Customer service and billing operations
Delivery charges can include both fixed components and per-therm components. That's why delivery can still feel "high" even when your therm usage is modest.
In places where supplier choice exists, delivery is still paid to the local utility because they operate the physical distribution system.
Customer charges and other fixed fees
Many bills include a fixed monthly customer charge (sometimes called a base charge). Think of it as the "keep the account and service active" fee. It supports the fixed costs of being connected.
This is also why bills don't scale perfectly with usage. Cutting usage helps, but it won't eliminate fixed costs.
Why your total can change even if your usage doesn't
If you used about the same therms but your total changed, one of these is usually responsible:
- Rate changes: supply and/or delivery rates adjusted.
- Billing days: the cycle was longer or shorter.
- Estimated reads: usage shifted due to corrections.
- Seasonal pricing: winter demand often affects costs.
In winter, usage changes and rate changes often happen together. If you're dealing with a winter spike, the most useful guide iswhy gas bills spike in winter.
What to check on your bill (a short, practical checklist)
- Confirm the billing period length (days).
- Note total therms and calculate therms per day.
- Compare supply price per therm to last month.
- Compare delivery rates/fees to last month.
- Check whether the meter read was estimated.
If the units on your bill are confusing (CCF/MCF/therms), readMCF vs CCF vs thermsbefore you try to do any deeper comparisons.
Common line item names (what they usually mean)
Utilities don't all label charges the same way. Here are common names you might see and the category they typically fall under. This isn't a legal definition, but it's a useful decoding key when you're trying to understand your own statement.
- Commodity / Gas cost / Supply: the fuel itself.
- Distribution / Delivery / Transportation: local network service that brings gas to your address.
- Customer charge / Basic service: a fixed monthly charge for being connected.
- Rider / Adjustment / Surcharge: a component that may change periodically (often tied to specific programs).
- Taxes / franchise fees: government-related add-ons.
If your bill includes both supply and delivery, compare the two sections separately month to month. That habit prevents a lot of confusion, because a big jump in one section can hide inside a stable overall total.
If you can choose a supplier: what changes (and what doesn't)
In some areas, customers can choose a competitive supplier for the supply portion. If you're in a supplier-choice market, this is the key rule of thumb:
Choosing a supplier typically affects supply charges, not delivery charges.
You still pay the local utility for delivery because they own and operate the distribution system. That's why people sometimes switch suppliers and are surprised the bill doesn't drop as much as expected: delivery can be a large fraction of the total.
If you're evaluating an offer, compare:
- Price per therm
- Contract length and early termination terms
- Fixed vs variable rate structure
- Any monthly fees independent of usage
Even if you don't have supplier choice, the same idea applies when you compare months: keep supply and delivery separate so you can see whether usage drove the change or pricing/fees did.
A sample bill walkthrough (fictional numbers)
Suppose your bill shows these simplified lines:
- Usage: 60 therms
- Supply: $1.40/therm
- Delivery: $0.65/therm
- Customer charge: $15.00
A quick estimate of the pre-tax total looks like:
- Supply cost: 60 x 1.40 = $84.00
- Delivery variable: 60 x 0.65 = $39.00
- Fixed customer charge = $15.00
That's about $138 before taxes and fees. Now notice what happens if usage drops to 30 therms: your variable portions cut in half, but the $15 fixed charge remains. This is why bills don't scale perfectly with conservation.
If your total is spiking specifically in winter, pair this supply vs delivery framework withthe winter spike guideto see whether the driver is more therms, higher rates, or both.
Find your marginal cost per therm (the number that matters)
If you're trying to decide whether a change is "worth it" (lowering the thermostat, sealing drafts, changing suppliers), you need one key number: your marginal cost per therm.
In plain terms, marginal cost per therm is: how much your bill changes if you use one fewer therm. Fixed charges don't change with usage, so they don't belong in that calculation.
How to estimate it from your bill
- Find the supply price per therm (or commodity rate).
- Find delivery charges that are per therm (some are fixed, some are variable).
- Add the per-therm components together.
For example, if supply is $1.40/therm and variable delivery is $0.65/therm, your marginal cost is about $2.05 per therm(before taxes). That's the number you use to estimate savings from reducing therms.
If your bill doesn't clearly show the per-therm delivery pieces, don't panic. The exact number varies by utility, but even a rough estimate is better than guessing.
What you can control (and what you usually can't)
Gas bills are frustrating because not every part responds to your behavior. Here's a realistic breakdown.
You can usually control
- Therms used: thermostat settings, run time, drafts, equipment maintenance, hot water habits.
- Supply price (sometimes): by choosing a supplier in supplier-choice markets, or by understanding plan types.
You can't usually control
- Fixed customer charges: they apply when you're connected.
- Delivery system costs: delivery rates are set through utility rate processes and tend to be stable month-to-month but can change over time.
- Weather: but you can normalize comparisons by using therms per day.
If your main concern is a winter spike, pairing this section withthe winter spike playbookwill usually point you to the most likely "control knob."
Questions to ask if your bill suddenly changed
If your total changed sharply and you can't immediately explain it through therms used or obvious rate changes, these questions usually get you to a useful answer faster.
- Was this month's meter read actual or estimated?
- Did the billing cycle have an unusual number of days?
- Were there prior-period adjustments or corrected reads?
- Did the supply rate change due to a periodic gas cost adjustment?
- Did any delivery riders or surcharges change this cycle?
You don't need to become a rate expert. The point is to learn whether the change came from usage (therms), pricing (per-therm rates), timing (days/reads), or one-time corrections.
Common misconceptions about delivery vs supply
- "Delivery is a fake fee." Delivery funds the distribution system (pipes, maintenance, safety programs).
- "Choosing a supplier removes delivery charges." In many markets, supplier choice affects supply, not delivery.
- "My therm usage is the only thing that matters."Fixed charges and rate changes can materially affect the total.
Frequently asked questions
The supply charge (commodity charge) is the cost of the natural gas fuel itself, usually priced per therm.
