Which Fuel Is Currently Cheaper Per BTU?
Natural gas is currently cheaper per BTU than heatypes of heating systems ting oil in most U.S. boiler replacement costmarkets, cosfurnace installation cost ting approximately $6–$10 per million BTU versus $10–$15 per million BTU for heating oil. However, fuel prices vary by region and fluctuate with market conditions—and in some rural areas of the Northeast and Upper Midwest where oil is the dominant heating fuel, gas may not be available at all.
Fuel Price Comparison (2024–2025 approximate ranges)
| Fuel | Price per Unit | BTU per Unit | Price per Million BTU |
|---|---|---|---|
| Natural Gas | $1.20–$1.80/therm | 100,000 BTU/therm | $6–$9 |
| Heating Oil | $3.20–$4.50/gallon | 138,500 BTU/gallon | $10–$15 |
| Propane | $2.00–$3.00/gallon | 91,500 BTU/gallon | $11–$17 |
Natural gas has the lowest fuel cost per BTU where it’s available. Heating oil is more expensive per BTU but delivers more energy per gallon, making it comparable on volume usage.
Which Furnace Type Has Higher Efficiency Ratings?
Modern condensing <a href="/gas-furgas furnaces naces-2/”>gas furnaces reach 95–99% AFUE, while oil furnaces typically range from 83% to 89% AFUE for standard models and up to 95% AFUE for high-efficiency condensing units. The efficiency gap between gas and oil has narrowed in recent years as high-efficiency oil furnaces have improved.
Efficiency Comparison
| Furnace Type | AFUE Range | Typical Category |
|---|---|---|
| Standard gas | 80–84% | Non-condensing |
| Mid-efficiency gas | 85–89% | Non-condensing |
| High-efficiency gas | 90–99% | Condensing |
| Standard oil | 83–86% | Non-condensing |
| High-efficiency oil | 87–95% | Condensing |
One key distinction: oil furnaces burn hotter than gas, which can cause more wear on components over time, potentially affecting longevity. However, modern oil burners are engineered to manage this heat output effectively.
What Maintenance Does Each Type Require?
Oil furnaces require more frequent and more intensive maintenance than gas furnaces. The combustion characteristics of oil—higher particulates, more soot, acidic byproducts—mean components soil faster and inspection intervals are shorter.
Oil Furnace Maintenance Requirements
- Annual professional service is essential — oil combustion produces significant soot that accumulates on burners, nozzle assemblies, and heat exchangers
- Nozzle replacement annually — oil nozzles are wear items that degrade over time and affect spray pattern and combustion quality
- More frequent filter changes — particularly important with oil to prevent nozzle clogging
- Annual combustion analysis — verify CO and combustion efficiency; more critical than with gas
- Oil tank inspection — above-ground or underground tanks should be checked for leaks, water accumulation, and sediment
Gas Furnace Maintenance Requirements
- Annual professional service — same as oil for safety and efficiency monitoring
- Nozzle/ burner cleaning — gas combustion is cleaner; less frequent cleaning needed
- Standard filter changes — monthly to quarterly depending on filter type
- Combustion analysis — verify proper gas pressure and no dangerous CO levels
- Condensate drain maintenance (condensing units) — flush annually to prevent clogs
Which Furnace Type Works Better in Cold Climates?
Both gas and oil furnaces perform effectively in cold climates, as they generate heat through combustion regardless of outdoor temperature. Neither has the “cold weather limitation” that air-source heat pumps do—the fuel burns regardless of how cold it is outside.
The choice between gas and oil in cold climates comes down to:
- Fuel availability — gas may not be available in rural areas; oil is often the only option
- Fuel cost — gas is usually cheaper per BTU even in cold climates
- Storage requirements — oil requires an on-site storage tank (underground or above-ground); gas is piped in from a utility
- Delivery logistics — oil requires scheduled deliveries; running dry in extreme cold is a risk without proper monitoring
In northern states (Maine, Vermont, New Hampshire, northern New York, Michigan, Wisconsin, Minnesota), oil furnaces remain common precisely because natural gas distribution infrastructure never reached many rural and semi-rural areas. For homeowners in these regions, the gas-vs-oil comparison is partly academic—oil may be the only practical choice.
Frequently Asked Questions
Is it worth converting from oil to gas?
Converting from oil to gas can cost $4,000–$10,000 including gas line installation, new venting, and furnace replacement—but the long-term fuel savings often justify the investment in areas where gas is significantly cheaper than oil. Consider consulting our guide to the besbest gas furnaces 2025 t gas furnaces of 2025 if you’re considering the switch. The payback period depends on current oil costs, projected gas costs, how long you plan to stay in the home, and the cost of the gas line installation (the biggest variable).
Get at least three quotes from licensed HVAC and gas fitting contractors before committing. The existing oil tank and chimney may need to be decommissioned, which adds cost.
Which lasts longer, gas or oil furnace?
Both gas and oil furnaces have similar average lifespans of 15–20 years with proper maintenance. Oil furnaces may experience slightly higher wear from hotter combustion temperatures, but modern units are engineered to manage this. The maintenance quality matters more than the fuel type.
Does an oil furnace produce more carbon monoxide?
Both oil and gas furnaces produce trace amounts of CO during combustion—proper ventilation and annual inspections prevent dangerous accumulation. Oil furnaces can produce more particulates if the burner is dirty or the nozzle is worn, which can affect combustion quality. Annual combustion analysis is critical for both fuel types.
Can I use an oil furnace if gas becomes available later?
Converting from oil to gas later is possible but involves significant cost: running a gas line (if not already available), modifying or replacing the furnace, and updating the venting system. It’s not a simple swap. If gas is coming to your area, many homeowners choose to convert at the point of furnace replacement to minimize the disruption and cost.
Are there high-efficiency oil furnaces?
Yes—high-efficiency condensing oil furnaces reach 90–95% AFUE. These units use a secondary heat exchanger to extract additional heat from exhaust gases, similar to high-efficiency gas furnaces. They require oil-to-water heat exchangers and more complex venting, and they cost more than standard oil furnaces. For homeowners in oil-only areas who heat heavily in winter, the fuel savings over a 15-year furnace life often justify the higher upfront cost.
