In winter seasons there is much need of components like water heaters, gas furnaces and heat pumps. Homeowners who rely on gas furnaces and why they face higher gas bills they thought that it is due to furnace which uses gas. So the truth is that gas and propane only delivers heat modern furnaces also consume electricity for working effectively. That’s why understanding how many watts does a gas furnace use helps you to manage your bills, selecting suitable generators and preparing for power outages.
So in this guide by MileHi HVAC we will explain average wattage and how you can reduce your operating cost by keeping your comfort.
Average watts of a gas furnace
A standard gas furnace normally uses 400 to 1200 watts while running. However many homes have furnaces in the 600 to 800 watt range. But this wattage depends upon different variables like furnace size, efficiency rating and blower motor.
In gas furnaces gas is used as primary source for giving heat and electricity is used for some elements like ignition, airflow and safety concerns. So this system is known as gas furnace wattage which is typical at lower level than electrical heating systems.
Electrical Components and their power use
| Component | wattage | purpose |
| Blower motor | 300–750 watts | Moves warm air |
| Ignition System | 80–120 watts | Lights burners |
| Control Board | 20–50 watts | Manages heating cycle |
| Draft Inducer | 50–100 watts | Vents exhaust |
| Transformer | 10–20 watts | Powers thermostat |
Keep this thing in mind that startup wattage is higher than running wattage. When the furnace starts it draws 1.5 to 2 times than normal operating power. So consider this factor while choosing a backup generator.
At Milehi Hvac, we see many homeowners surprised by their furnace’s electrical needs. Our furnace installation services in Denver include detailed power consumption analysis to help you choose the most efficient system for your home.
Gas Furnace Wattage by Size and BTU Rating
As gas furnace wattage depends upon various factors so gas furnace electricity usage directly depends upon the furnace size. Lager furnaces typically require more powerful blowers which leads to increase in electrical consumption.
BTU and wattage of furnaces
- 40,000-60,000 BTU have wattage of 400-600 watts.
- 60,000-100,000 BTU have wattage of 600-900 watts.
- 100,000-150,000 BTU have wattage of 900-1200 watts.
So high efficiency furnaces which have AFUE ratings above 90% often use variable speed ECM blower motors. These types of motors also reduces electrical demand by 30-50 percent
Average Wattage by Furnace Type
Comparing different heating systems shows why gas furnaces are energy-smart.
| Heating System | Wattage Range | Energy Source |
| Gas Furnace | 400-1,200 watts | Natural gas + electricity |
| Electric Furnace | 10,000-50,000 watts | Electricity only |
| Oil Furnace | 800-1,400 watts | Heating oil + electricity |
| Heat Pump | 3,000-5,000 watts | Electricity only |
| Propane Furnace | 400-1,200 watts | Propane + electricity |
Gas furnaces offer the best balance. They use 400-1,200 watts of electricity while natural gas provides the actual heat. The gas furnace wattage stays relatively low because electricity only powers auxiliary systems.
Electric furnaces are power-hungry. They consume 10,000-50,000 watts because electricity generates all the heat. A typical 15,000-watt electric furnace costs significantly more to operate than a comparable gas unit.
You may read How Long Does A Gas Furnace Last?
Factors Increasing Furnace electrical use
Due to the following several factors your furnace will consume more electricity.
Blower Motor
Old motors run on full power with 400 to 800 watts. But modern ECM motors run and use power according to the demand, often using 200 to 600 watts. So this is reducing the gas furnace wattage over time.
Climate and runtime
Electrical consumption also depends upon the time you are using the furnace. Mostly in colder regions, furnaces run all the time almost 8 to 12 hours. So a longer runtime also leads to more usage of electrical power.
Duct Condition and house insulation
Even though the gas is still delivering heat but due to poor insulation and leaky ducts the furnace will run longer cycles compared to normal operating systems. As a result, blower runtime raises gas furnace electrical usage.
Lifespan and maintenance
Regular maintenance matters a lot because with dirty filters and dust buildup electrical usage increases by almost 10-25% so with proper inspection and maintenance the motor will run effectively without any cost.
Calculating Your Gas Furnace Electricity Cost
Knowing your actual costs helps with budgeting and generator planning.
Step 1: Find your furnace’s wattage rating on the data plate inside the blower compartment door. Look for voltage and amperage. Multiply these numbers together. A furnace running on 120 volts at 5 amps uses 600 watts.
Step 2: Estimate daily runtime hours. Most furnaces run 6-10 hours per day in winter.
Step 3: Calculate daily kilowatt-hours. Multiply wattage by hours and divide by 1,000. A 700-watt furnace running 8 hours uses 5.6 kWh daily (700W × 8 hours ÷ 1,000).
Step 4: Find your electricity rate on your utility bill. The national average is 17 cents per kWh. Denver residents typically pay 12-14 cents per kWh.
Step 5: Multiply daily kWh by your rate and days per month. That 5.6 kWh furnace costs about 76 cents daily at 13.6 cents per kWh. Over a 30-day month, that’s $22.80 just for the electrical portion.
| Daily Runtime | Monthly kWh (700W furnace) | Monthly Cost (14¢/kWh) |
| 6 hours | 126 kWh | $17.64 |
| 8 hours | 168 kWh | $23.52 |
| 10 hours | 210 kWh | $29.40 |
| 12 hours | 252 kWh | $35.28 |
Picking the Right Generator for Your Furnace
If the electricity fails during winter you won’t want to be left cold. A generator ensures your furnace operates when the power grid is, off.
What Size Is Necessary? Calculate your furnace’s wattage during operation. Then increase that by 25%. This additional margin accounts, for the power spike when the motor starts. For example with a 700-watt furnace your generator should supply least 875 watts.
What Individuals Truly Purchase:
- For furnaces using 400-600 watts opt for a generator rated, between 1,500 and 2,000 watts.
- Sized models that consume 600-900 watts—opt for 2,000 to 2,500 watts instead
- Larger furnaces, with 900-1,200 watts—ideally you need 3,000 to 3,500 watts
The majority of households manage well with a 2,000-watt generator. It can operate your furnace. Still provide sufficient power for a few lights and your refrigerator when the rest of the power is out.
If you want the whole house covered, standby generators start around 7,500 watts. These things kick on automatically when the power drops and can handle your entire electrical panel without you lifting a finger.
How to reduce furnace electrical demand
- Use a variable speed ECM motor
- Replace air filters every month
- Seal the duct leaks
- Install a small thermostat
- Schedule annual maintenance with professionals
When replacement time comes, Milehi Hvac offers furnace installation services in Denver with detailed energy savings analysis.
Conclusion
A typical gas furnace uses 400–1,200 watts of electricity with most homes averaging 600–800 watts during operation. This adds roughly $20–40 per month to winter electricity bills.
Knowing how many watts does a gas furnace use allows homeowners to budget accurately, select proper backup power and make informed efficiency upgrades. With proper maintenance and modern equipment, gas furnaces remain one of the most cost-effective heating solutions available.
Need expert help choosing an energy-efficient furnace? Contact Milehi Hvac for professional furnace installation services in Denver. We’ll help you find the perfect system to reduce costs and keep your home warm all winter.
FAQs
Will a 2000-watt generator run a gas furnace?
Yes, a 2000-watt generator handles most residential gas furnaces comfortably. Standard furnaces use 600-800 running watts with starting surges around 900-1,200 watts. This leaves enough capacity for a few lights and small appliances.
How many amps does a gas furnace use?
Gas furnaces typically draw 5-15 amps at 120 volts. Smaller units use 5-8 amps while larger systems with powerful blowers draw 10-15 amps. High-efficiency models with ECM motors often use fewer amps.
Can a gas furnace run without electricity?
No, modern gas furnaces cannot operate without electricity. They need power for the ignition system, blower motor, and safety controls. Even though natural gas provides the heat, electrical components are essential for safe operation.
Can a 3500 watt generator run a gas furnace?
Yes, a 3500-watt generator can run most gas furnaces since they mainly power the blower and controls. Make sure it can handle the furnace’s startup (surge) wattage.
Can I plug my gas furnace into a generator?
Yes, but only through a proper transfer switch or interlock for safety. Never plug directly into an outlet without approved electrical protection.
Will a 5000 watt generator run a gas furnace?
Yes, a 5000-watt generator can easily run a gas furnace and other essentials. It provides enough capacity for startup surges and additional appliances.
