Natural Gas Bill Increase Calculator: Percentage Change in Your Bill
Work out the percentage increase in your natural gas bill between two periods — and the dollar difference — so you can tell whether it's higher gas prices, more usage from cold weather, or a delivery-rate change driving the cost up.
Adjust the inputs and select Calculate for a full breakdown.
Compare Common Scenarios
How the numbers shift across typical situations for this calculator:
| Scenario | Bill increase | Dollar change |
|---|---|---|
| $90 to $108 (+20%) | 20.00% | 18 |
| $60 to $150 (+150%, winter heating) | 150.00% | 90 |
| $110 to $121 (+10%, rate hike) | 10.00% | 11 |
| $80 to $88 (+10%) | 10.00% | 8 |
How This Calculator Works
Enter your previous bill and your new bill for comparable periods. The calculator finds the percentage increase and the dollar difference. For a fair comparison, use the same billing-period length and be aware that weather strongly affects gas usage.
The Formula
Percentage Change
Old is the starting value, New is the ending value
Worked Example
A natural gas bill rising from $90 to $108 is a 20% increase — $18 more for the period. Gas bills move for a few reasons: the commodity (gas) price changed, your usage rose (a cold snap means more heating), or the utility's delivery/distribution rates increased. Winter bills are far higher than summer ones for heating homes, so always compare similar seasons — a 'huge increase' from October to January is mostly more heating, not necessarily higher rates.
Key Insight
Natural gas bills are split into two parts, and understanding the split is key to diagnosing an increase: the commodity charge (the gas itself, which fluctuates with volatile wholesale markets) and the delivery/distribution charge (the utility's regulated cost to pipe it to you). A bill jump could be the gas price spiking (often seasonal or driven by supply events), the regulated delivery rate rising, or simply higher usage from colder weather. To separate them, compare the per-unit (per therm or per CCF) gas cost and your usage volume across the two bills — many bills break this out. If it's usage, conservation helps: a programmable/smart thermostat, sealing drafts and adding insulation, lowering the heat a few degrees, and water-heater efficiency all cut gas use, with heating being the dominant driver in cold climates. If it's the commodity price, some areas let you choose a competitive gas supplier or lock a fixed rate, which can hedge volatility. Compare similar seasons (winter to winter), since the biggest swings are weather-driven. The percentage shows the jump's size; pinpointing whether it's price, rate, or usage tells you whether to conserve, shop suppliers, or simply expect it to fall when the weather warms.
Frequently Asked Questions
How is the natural gas bill increase calculated?
Subtract the old bill from the new bill, divide by the old bill, and multiply by 100. From $90 to $108 is ($108 − $90) / $90 = 20%, an $18 increase for the period.
Why did my natural gas bill go up?
Three main reasons: the commodity (gas) price rose, your usage increased (colder weather means more heating), or the utility's delivery/distribution rate changed. Compare the per-unit gas cost and your usage volume across bills to see which is driving the increase — many bills break out these parts.
Why are winter gas bills so much higher?
Because heating is the dominant use of natural gas in cold-climate homes, so winter usage far exceeds summer. A big increase from autumn to mid-winter is mostly more heating, not necessarily higher rates. Compare similar seasons (winter to winter) for a fair read on whether rates actually changed.
How can I lower my natural gas bill?
If it's usage: a programmable or smart thermostat, sealing drafts, adding insulation, lowering the heat a few degrees, and an efficient water heater all cut gas use. If it's the commodity price, some areas let you choose a competitive supplier or lock a fixed rate to hedge volatile wholesale prices.
What's the difference between supply and delivery charges?
The supply (commodity) charge is for the gas itself and fluctuates with wholesale markets; the delivery/distribution charge is the utility's regulated cost to pipe it to your home. A bill increase can come from either, plus your usage — separating them tells you whether to shop suppliers, expect regulated rate changes, or conserve.
Related Calculators
Methodology & Review
The increase is the change between the old and new bill divided by the old bill, multiplied by 100. It compares two bills directly and does not separate a commodity-price change from higher usage (e.g. colder weather) or delivery-rate changes.
Written by Ugo Candido · Last updated May 22, 2026.