Why Is My Gas Bill So High? 10 Common Causes and How to Fix Each One
Troubleshoot a high natural gas bill step by step. Covers furnace efficiency, thermostat settings, water heater waste, rate changes, and seasonal spikes with real cost estimates.
Why Is My Gas Bill So High? 10 Common Causes and How to Fix Each One
A high gas bill usually comes down to one of three things: you’re using more gas than usual, your equipment is wasting gas, or your rate went up. This guide helps you figure out which one — and what to do about it.
Natural gas bills are measured in therms (1 therm = 100,000 BTU) or CCF (hundred cubic feet). One CCF ≈ 1.037 therms. For most households, the difference is negligible — but knowing your units helps when comparing bills.
Table of Contents
- Quick diagnosis: Start here
- 10 common causes, ranked by likelihood
- How to read your gas meter
- Understanding gas rate structures
- Cost and savings math
- When to call your gas utility
- FAQ
Quick diagnosis: Start here
Answer these four questions before diving into troubleshooting:
Did your therm usage actually increase? Compare the “usage” line (in therms or CCF) with the same month last year. If therms are flat but your bill went up, the issue is rate or fee changes — not your equipment.
How cold was this month compared to last year? Gas usage is dominated by heating. A month that’s 5°F colder on average can increase your gas usage by 15–25%. Check heating degree days (HDD) data from Weather Underground for your zip code.
Is your meter read actual or estimated? Estimated reads can be inaccurate. An overestimate this month will be corrected next month, but it can cause a confusing spike.
Did anything change? New thermostat, new furnace, someone working from home, a guest staying over, thermostat set higher than usual, or a renovation can all increase usage.
10 common causes, ranked by likelihood
1. Heating season weather
This is the #1 cause of gas bill spikes. Heating accounts for 60–70% of natural gas usage in a typical home. A cold snap in November or December can double your usage compared to a mild month.
What to check:
- Compare this year’s average temperature with last year for the same billing period.
- Check if your billing period included an unusually cold week.
- Look at “heating degree days” (HDD) — a standard measure of heating demand. Your utility may include this on your bill.
What to do:
- If weather is the cause, focus on efficiency improvements (insulation, thermostat settings) rather than looking for a “problem.”
2. Thermostat settings too high
Every degree above 68°F increases heating energy use by roughly 3–5%. If you keep your home at 74°F instead of 68°F, you’re using about 18–30% more gas for heating.
Recommended settings:
- When home: 68°F (20°C)
- When sleeping or away: 60–62°F (15–17°C)
- Maximum savings: 65°F when home, 55°F when away
Programmable thermostat tip: Set it to drop 5–8°F when you’re sleeping or away. This alone can save 10–15% on heating costs. If you have a smart thermostat (Nest, Ecobee, Honeywell Home), enable the eco/schedule feature.
3. Furnace efficiency decline
Furnaces lose efficiency as they age. A furnace rated at 92% AFUE (Annual Fuel Utilization Efficiency) may drop to 80–85% after 10–15 years without proper maintenance.
Signs your furnace is wasting gas:
- Runs longer to reach the target temperature
- Uneven heating (some rooms cold, others hot)
- Yellow flame instead of blue (incomplete combustion — also a safety concern)
- Soot around the furnace or vents
- Increasing gas usage year over year despite same habits
What to do:
- Annual maintenance ($80–$200) — A professional tune-up can restore 2–5% efficiency and catch problems early.
- Filter replacement — A dirty filter forces the furnace to work harder. Replace every 1–3 months during heating season.
- Consider replacement — If your furnace is 15+ years old, a new 95–98% AFUE model can cut gas usage by 20–30%. Typical cost: $3,000–$6,000 installed, with payback in 5–8 years through gas savings.
4. Poor insulation and air leaks
Your furnace may be working correctly, but you’re losing heat through:
- Attic insulation — The #1 source of heat loss in most homes. If you have less than R-38 (about 10–14 inches of fiberglass), adding insulation pays for itself in 1–3 years.
- Windows and doors — Weatherstripping and caulking cost $20–$50 and can reduce drafts significantly.
- Recessed lights — Can lights in ceilings below attics are notorious for air leakage.
- Ductwork leaks — Leaky ducts in unconditioned spaces (attics, crawl spaces) can waste 20–30% of your heated air.
Quick test: On a cold windy day, hold a lit incense stick near windows, doors, electrical outlets on exterior walls, and any penetrations. Smoke moving horizontally indicates an air leak.
5. Gas water heater waste
Water heating is typically the second-largest gas expense (15–25% of gas usage). Common waste sources:
- Temperature set too high — Many water heaters are set to 140°F by default. Lowering to 120°F saves 4–22% on water heating costs with no noticeable difference in comfort.
- Sediment buildup — Minerals settle at the bottom of the tank, creating an insulating layer between the burner and water. Flush the tank annually.
- Old and inefficient — Standard tank water heaters are 58–65% efficient. A tankless condensing model can be 95–98% efficient.
- Leaking T&P valve — If the temperature and pressure relief valve is dripping, the heater is over-pressurizing and wasting hot water.
6. Rate increase
Natural gas prices are volatile. Your utility’s “gas cost recovery” rate can change monthly or quarterly. In 2025, many US utilities increased rates by 15–30% compared to 2024.
What to check on your bill:
- Cost per therm — Compare with the same month last year.
- Delivery charges — Your utility may have raised the fixed delivery charge.
- Pipeline or infrastructure surcharges — Becoming more common.
- Weather normalization adjustment — Some utilities smooth out weather impacts; others don’t.
What to do: If rates increased significantly, check if you’re in a deregulated state where you can choose a gas supplier. You may be able to lock in a lower rate through a third-party supplier.
7. Gas leak (safety concern)
A gas leak is both a safety emergency and a source of wasted gas. Signs include:
- Rotten egg smell — Mercaptan, the odorant added to natural gas.
- Hissing sound — Near gas lines, valves, or appliances.
- Dead vegetation — Plants dying near an underground gas line.
- Higher-than-expected usage — Even a small leak adds up over a billing period.
⚠️ If you smell gas: Leave the house immediately. Don’t use light switches, phones, or anything that could create a spark. Call your gas utility’s emergency line (or 911) from outside.
8. Gas fireplace or logs left on
Gas fireplaces and decorative gas logs use 25,000–60,000 BTU/hour. Leaving a gas fireplace on overnight (8 hours) at 40,000 BTU uses about 3.2 therms — roughly $3–$5/night depending on your rate. Over a month, that’s $90–$150.
Check: Make sure your gas fireplace is completely off (pilot lights on older models also consume gas continuously — about 600–900 BTU/hour, which adds up to $10–$20/month).
9. Drafty or inefficient windows
Single-pane windows or old double-pane windows with failed seals let significant heat escape. Replacing windows is expensive ($300–$1,000/window), but low-cost alternatives help:
- Window film insulation kits — $15–$30 per window, reduces heat loss by 40–70%.
- Thermal curtains — $20–$60 per window, blocks drafts and radiant heat loss.
- Weatherstripping — $5–$15 per window, seals gaps around the frame.
10. Billing cycle length or estimated readings
A 35-day billing period will naturally cost more than a 28-day period. And estimated readings can be wildly off if your usage pattern changed.
What to check:
- “Days of service” on your bill
- Whether the read was actual or estimated
- If estimated, the next actual read will correct any overcharge
How to read your gas meter
Gas meters measure usage in cubic feet. The display has 4–5 dials or a digital readout.
Analog meter
- Read the dials left to right
- If a pointer is between two numbers, use the lower number
- If a pointer is directly on a number, check the dial to its right — if that dial hasn’t passed 0, use the number before
Digital meter
- Simply read the numbers displayed
- Some smart meters cycle through multiple displays — look for the consumption reading (usually labeled “usage” or showing a gas flame icon)
Tracking usage between bills
- Read your meter on the same day each month.
- Subtract last month’s reading from this month’s.
- Multiply by the conversion factor (if billed in therms, multiply cubic feet by 1.037).
Understanding gas rate structures
Fixed rate
You pay a set price per therm for the duration of your contract. Predictable but may be higher than market rate when prices drop.
Variable rate
Your rate changes monthly based on market prices. Can be cheaper during low-demand periods but risky during cold winters or supply disruptions.
Budget billing
Your utility averages your annual costs into equal monthly payments. You pay the same amount each month, with a “true-up” at the end of the year. This doesn’t save money, but it prevents winter shock bills.
Delivery vs. supply
Your gas bill has two main components:
- Supply charges — The cost of the gas itself. In deregulated states, you can shop for this.
- Delivery charges — The cost of transporting gas to your home. This is set by your utility and regulated by your state’s public utility commission.
Cost and savings math
| Fix | Monthly Savings | Upfront Cost | Payback Period |
|---|---|---|---|
| Lower thermostat to 68°F from 72°F | $15–$40 | $0 | Immediate |
| Programmable thermostat schedule | $20–$50 | $25–$250 | 1–6 months |
| Annual furnace maintenance | $10–$25 | $80–$200 | 4–12 months |
| Water heater temp: 140°F → 120°F | $5–$20 | $0 | Immediate |
| Weatherstripping doors/windows | $10–$30 | $20–$50 | 1–3 months |
| Attic insulation (R-11 → R-38) | $30–$80 | $1,000–$2,500 | 1–3 years |
| New 96% AFUE furnace (replacing 70% AFUE) | $40–$100 | $3,000–$6,000 | 3–8 years |
Example scenario:
- Old furnace: 70% AFUE, using 120 therms/month in winter at $1.20/therm = $144/month
- New furnace: 96% AFUE, using 87.5 therms/month = $105/month
- Monthly savings: $39
- Annual savings (5-month heating season): $195
- At a $4,500 installation cost, payback: ~23 years (gas-only savings)
- With electric savings from the blower motor and potential rebates: 8–12 years
When to call your gas utility
Contact your gas utility when:
- You suspect a gas leak — Call the emergency line immediately. Don’t wait.
- Your meter appears damaged or reading incorrectly — Request a meter inspection.
- You want a billing review — They can explain rate changes and check for errors.
- You need help with payment — Most utilities offer payment plans and assistance programs (LIHEAP) for income-qualified customers.
- You want to switch rate plans — Ask about fixed-rate options or budget billing.
- You suspect an estimated reading was wrong — Request an actual read.
FAQ
What’s a normal gas bill?
The average US household gas bill ranges from $40–$80/month in summer (mostly water heating and cooking) to $100–$250/month in winter (heating-dominated). Bills in cold climates (Minnesota, Michigan, New York) can exceed $300/month in peak winter.
Why is my gas bill high in summer?
If your gas bill stays high in summer, the most likely culprits are your gas water heater (check temperature settings) or a gas fireplace pilot light left on. Other possibilities: gas dryer used frequently, gas stove/oven used heavily, or a small gas leak.
Should I switch to electric heat?
It depends on your local electricity rates, climate, and insulation quality. In areas with cheap electricity and moderate winters, a heat pump can save significantly. In cold climates with expensive electricity, gas heating may remain cheaper. See our guide on gas vs electric heat cost comparison.
How do I know if my furnace needs replacing?
Consider replacement if:
- It’s more than 15–20 years old
- Your gas bills have been steadily increasing despite same usage habits
- Repair estimates exceed $500–$1,000
- The heat exchanger is cracked (carbon monoxide risk — replace immediately)
Can I negotiate my gas rate?
In deregulated states (Ohio, Pennsylvania, Georgia, Michigan, New York, Illinois, and others), you can choose your gas supplier. Compare offers at your state’s public utility commission website. In regulated states, rates are set by the commission — you can attend public hearings or file comments during rate cases.
Related guides
- How to Read Your Gas Bill — Detailed bill breakdown
- Why Is My Electric Bill So High? — Troubleshoot electricity costs
- How to Lower Utility Bills — Comprehensive savings strategies
- Fixed vs Variable Utility Rates — Choose the right rate plan
- Hidden Fees on Your Utility Bill — Find charges you can dispute
Bottom line: The fastest way to reduce your gas bill is to lower your thermostat by 2–4°F and replace your furnace filter. These two steps take less than 30 minutes and can save 5–15% on heating costs immediately. For long-term savings, invest in insulation and consider upgrading to a high-efficiency furnace when yours reaches end of life.
