A gas furnace uses electricity for controls, the blower motor, ignition, and safety devices while burning natural gas or propane for heat. Understanding the monthly electricity use helps homeowners estimate utility costs, compare systems, and plan efficiency upgrades. This article breaks down energy use by component, typical monthly kWh ranges, factors that influence consumption, and practical ways to reduce electrical demand.
| Furnace Component | Typical Power Draw | Estimated Monthly kWh |
|---|---|---|
| Control Board/Igniter | 50–200 watts (intermittent) | 5–15 kWh |
| Draft/blower Motor (ECM variable) | 200–1,200 watts (varies) | 30–300 kWh |
| Humidifier/Accessories | 20–200 watts | 5–50 kWh |
| Average Combined Monthly Use (Mild Winter) | — | 30–120 kWh |
| Average Combined Monthly Use (Cold Winter) | — | 120–400+ kWh |
How Gas Furnaces Use Electricity
A gas furnace relies on natural gas or propane for heat but still uses electricity for several critical functions. Typical electrical components include the electronic control board, electronic ignition (hot surface or intermittent pilot), blower motor to circulate warm air, and auxiliary devices like condensate pumps, thermostats, and humidifiers. Each component contributes to total monthly kWh consumption.
Key Components And Their Electrical Consumption
Control Board And Ignition
Control boards and electronic ignition systems draw power in short bursts during start-up and cycling. A hot-surface igniter may draw 50 to 120 watts for a few seconds to a minute each cycle, while intermittent pilot systems draw much less. Over a month, control and ignition systems typically account for 5–15 kWh depending on cycling frequency.
Blower Motor Types And Impact
The blower motor is the largest electrical consumer in a gas furnace. Two common motor types are permanent split capacitor (PSC) and electronically commutated motors (ECM). PSC motors are less efficient and may draw 600–1,200 watts at high speed. ECMs are variable-speed and more efficient, often drawing 200–600 watts depending on speed and airflow needs.
ECM motors can cut blower electrical use by 30–70% versus PSC motors, particularly in systems with long runtimes or variable-speed operation.
Accessories And Auxiliary Loads
Other electrical loads include whole-home humidifiers, electronic air cleaners, condensate pumps, and smart thermostats. Individually, these are modest—typically 10–200 watts each—but combined they can add 5–50 kWh per month.
Typical Monthly Electricity Use By Climate And Usage
Monthly electricity consumption for a gas furnace varies widely based on climate, thermostat settings, house insulation, and furnace efficiency. The figures below offer realistic ranges for U.S. climates.
Mild Climates
In mild climates with short heating seasons, a gas furnace may run minimally. Typical monthly electrical use for heating months is 30–120 kWh. Most consumption comes from the blower and intermittent ignition cycles.
Moderate Climates
For regions with moderate winters, monthly use often falls in the 80–200 kWh range. Longer runtimes and more frequent cycles increase blower energy consumption, especially with PSC motors or older systems.
Cold Climates
Homes in cold climates with extended heating seasons can see monthly electrical use for the furnace of 150–400+ kWh. Multi-family cycles, high fan runtime, and repeated ignition events push consumption higher.
Sample Calculations: How To Estimate Monthly kWh
Estimating monthly furnace electricity use requires assessing average wattage and runtime. The equation is simple: kWh = (Watts × Hours) / 1000. The examples below illustrate common scenarios.
Example 1: Efficient Furnace With ECM Motor
Assume an ECM blower averages 300 watts while running, control/ignition contributes 10 kWh monthly, and average runtime is 6 hours per day for 30 days. Fan energy = 300 W × 180 hours = 54,000 Wh = 54 kWh. Total = 54 + 10 = 64 kWh/month.
Example 2: Older Furnace With PSC Motor
Assume PSC blower at 800 watts, control/ignition 15 kWh, runtime 8 hours per day for 30 days. Fan energy = 800 W × 240 hours = 192,000 Wh = 192 kWh. Total = 192 + 15 = 207 kWh/month.
Example 3: Cold-Climate Heavy Use
Assume blower averages 600 watts, runtime 12 hours per day, control/ignition 20 kWh. Fan energy = 600 W × 360 hours = 216,000 Wh = 216 kWh. Total = 216 + 20 = 236 kWh/month. Additional accessories could add another 20–50 kWh.
Factors That Influence Electrical Consumption
Furnace Age And Efficiency
Older furnaces tend to have less efficient blower motors and outdated control systems, increasing electrical use. High-efficiency furnaces with ECM blowers and modern controls use significantly less electricity for the same heat output.
Fan Runtime And Thermostat Settings
Fan runtime drives electrical consumption. Continuous fan operation or high-speed settings increase kWh. Lower fan speeds, programmed fan cycles, or using the fan only during heating reduces electrical demand. Thermostat setback strategies can also reduce cycle frequency.
Home Insulation And Air Sealing
Well-insulated and air-sealed homes need less heating runtime, lowering blower operation and ignition cycles. Improving insulation, sealing drafts, and upgrading windows directly reduce furnace electrical use by reducing runtime.
Climate And Heating Load
Colder climates require more heat, increasing furnace runtime and electrical usage. Solar gain, local microclimates, and home orientation influence heating demand and thereby electricity use.
Accessory Equipment
Humidifiers, electronic air cleaners, and condensate pumps add to monthly kWh. Smart thermostats save energy by optimizing cycles, but Wi-Fi-enabled devices draw standby power that should be considered.
How To Measure Actual Furnace Electricity Use
Measuring actual use is the most accurate method. Several approaches provide reliable data at different cost and complexity levels.
Whole-House Smart Meter Data
Smart meters and utility usage portals often provide hourly or daily electricity usage. By comparing usage on days with similar conditions and isolating heating usage periods, homeowners can estimate furnace contribution.
Plug-In Energy Monitors
For plug-in accessories or external fans, smart plugs with energy monitoring provide direct kWh measurement. These are useful for humidifiers or standalone devices but not for hardwired furnace blowers.
Hardwired Whole-Furnace Metering
Installing a submeter or clamp-on kWh meter on the furnace circuit provides precise data for the control board and blower. An electrician can install a submeter or an advanced energy monitor to log real-time consumption.
Thermostat And Runtime Logs
Smart thermostats record runtime and cycle counts. By combining runtime with measured motor wattage (from manufacturer specs), an approximate kWh can be calculated.
Ways To Reduce Electricity Use From A Gas Furnace
Reducing furnace electricity reduces overall energy costs and environmental impact. Practical measures range from simple behavioral changes to equipment upgrades.
Replace PSC Motors With ECM
Upgrading to an ECM blower motor yields the biggest single reduction in electrical use for many systems. ECMs adjust speeds to match heating load, reducing unnecessary high-speed operation.
Install A High-Efficiency Furnace
Modern high-efficiency gas furnaces combine efficient heat exchangers and advanced controls, and often include ECM blowers. Replacing an old furnace can lower both gas and electricity use.
Use Smart Thermostat Controls
Smart thermostats optimize cycles, reduce runtime during unoccupied periods, and can integrate with other home systems to minimize fan runtime while maintaining comfort.
Optimize Fan Settings
Use the fan-on setting sparingly. Setting the fan to automatic reduces continuous motor operation. Lowering fan speeds where appropriate also cuts electrical draw.
Improve Home Envelope
Adding insulation, sealing air leaks, and upgrading windows reduce heating demand and furnace runtime. These improvements yield dual benefits for gas and electric savings.
Maintain The Furnace Regularly
Regular maintenance—cleaning filters, lubricating motors where applicable, and ensuring proper airflow—keeps the blower motor operating efficiently and reduces unnecessary electrical consumption.
Cost Implications And Comparison
To convert kWh to dollars, multiply monthly kWh by local electricity rates. For example, at $0.15 per kWh, a furnace using 200 kWh/month costs $30/month in electricity. In contrast, electric resistance heating using thousands of kWh would cost many times more.
Gas furnaces typically have lower electricity costs than electric heat pumps or baseboard electric heat for the same thermal output, because gas provides the primary thermal energy while electricity powers only controls and the blower.
When To Consider Upgrading Or Electrifying
Homeowners should consider upgrades when furnaces are old, blower motors are inefficient, or when monthly electrical use is unusually high. Electrification decisions should weigh local electricity prices, incentives, carbon goals, and the efficiency of heat pumps versus the combined gas-electric operation.
Incentive programs and rebates for ECM retrofits, high-efficiency furnace replacements, and whole-home electrification may offset upfront costs and improve long-term energy savings.
Practical Checklist For Homeowners
- Measure: Use smart meter data or a submeter to quantify furnace kWh.
- Inspect: Check blower motor type and age; PSC indicates higher consumption.
- Upgrade: Consider ECM blower retrofit or high-efficiency furnace replacement.
- Seal And Insulate: Reduce heating load and blower runtime.
- Optimize Thermostat: Use setback schedules and avoid continuous fan-on unless needed for filtration.
- Maintain: Change filters and schedule annual furnace tune-ups.
Resources And Next Steps
Homeowners seeking precise estimates should consult furnace specification sheets for motor wattage and contact licensed HVAC technicians for blower measurements. Local utilities and energy auditor programs often provide free assessments and rebates for efficiency upgrades.
Additional resources include the U.S. Department of Energy, local utility efficiency programs, and manufacturer data sheets for blower motors and furnace models to support accurate energy calculations.