Radon Fan Electricity Cost: What It Adds to Your Bill

Homeowners in Murfreesboro often ask the same thing after approving a radon system: what will it do to the power bill? The fan never shuts off. The EPA says it must run continuously for the system to work. That makes the cost easy to calculate once you know two numbers: the fan's wattage and what you pay for electricity.

Tennessee's electricity price

The U.S. Energy Information Administration's Electric Power Monthly (Table 5.6.A) lists Tennessee's average residential price at 13.42 cents per kWh for August 2026, up from 13.09 cents in August 2025. That's below the U.S. average of 18.16 cents. Your bill shows your own rate, and you can swap it into the math below.

What radon fans draw

RadonAway publishes wattage ranges for its RP series, which is common in residential systems:

• RP140, 4-inch: 17 to 21 watts
• RP145, 4-inch: 34 to 66 watts
• RP260, 6-inch: 47 to 65 watts
• RP265, 6-inch high-suction: 96 to 136 watts
• RP380, 8-inch high-airflow: 96 to 138 watts

Where your fan lands in its range depends on the resistance it works against. Dense clay soil under a slab, long pipe runs and multiple suction points push the draw up. Gravel under the slab or a well-sealed crawl space membrane can let a smaller fan do the job.

The math

Watts × 8,760 hours ÷ 1,000 = kWh per year. Then multiply by your rate. At 13.42 cents:

• 17 watts: about 149 kWh a year, roughly $20 (under $2 a month)
• 20 watts: about 175 kWh, roughly $24 ($2 a month)
• 34 watts: about 298 kWh, roughly $40 ($3.33 a month)
• 50 watts: about 438 kWh, roughly $59 ($4.90 a month)
• 66 watts: about 578 kWh, roughly $78 ($6.47 a month)
• 136 watts: about 1,191 kWh, roughly $160 ($13.32 a month)

Heating and cooling loss

The EPA's Consumer's Guide to Radon Reduction notes that most radon reduction systems cause some loss of heated or air-conditioned air, which can raise utility bills. How much depends on the climate, the system type and how the house is built. It also notes that fan systems are more effective and only slightly increase the electric bill. In Middle Tennessee, with hot, humid summers, that loss happens in both seasons. Air that leaks into the system through cracks, open sumps or unsealed crawl space membranes is air you paid to heat or cool. Angi estimates total energy costs of about $100 to $300 a year for a radon system, including that loss.

Keeping the cost down

• Seal openings. Sealing slab cracks, sump lids and crawl space membrane seams reduces how much house air the fan pulls. It also improves suction where it matters.
• Ask about diagnostics and fan sizing. A contractor who measures suction under the slab can choose the lowest-wattage fan that still meets the target. Ask what fan each bidder plans to use (see choosing a contractor).
• Never switch it off. Turning the fan off to save a few dollars lets radon return. The EPA says the fan should never be turned off.
• Watch for a failing fan. A worn fan may run but move less air. Check the manometer regularly. The EPA says fans may last five years or more and warranties rarely exceed five years.

Finding your own fan's wattage

If you already have a system, you can work out your own number in a few minutes:

1. Read the fan label. The fan is usually in the attic, the garage or on an outside wall, along the vent pipe. The model number is on the housing.
2. Look up the wattage. Manufacturers publish a watt range for each model. Use the middle of the range if you don't know your system's operating point.
3. Check your rate. Your electric bill lists the price per kWh, or you can divide the bill total by the kWh used.
4. Do the math. Watts × 8.76 × your price in dollars per kWh gives the yearly cost. A 50 watt fan at $0.1342 is 50 × 8.76 × 0.1342, or about $59.

If the fan plugs into an outlet rather than being hardwired, a plug-in electricity meter can measure the actual draw. Don't open a hardwired disconnect yourself; that's a job for an electrician.

Crawl spaces and townhomes

Crawl space systems in Rutherford County usually pull from under a sealed plastic membrane. A tight membrane helps the fan work efficiently, while a torn or loose one lets the fan pull more crawl space air than soil gas. In townhomes, a shared slab can affect fan sizing. Our crawl space and townhome guides explain both.

Is it worth it?

For a typical home, the electricity is about $25 to $80 a year, plus some heating and cooling loss. Compare that with the risk it lowers: in the EPA's lifetime-risk chart, about 62 in 1,000 smokers and 7 in 1,000 never-smokers would get lung cancer from a lifetime at 4 pCi/L. Our radon levels guide explains those numbers.

Frequently asked questions

How much does a radon fan cost per year in Tennessee?

At the EIA's August 2026 Tennessee average of 13.42 cents per kWh, about $20 a year for a 17 watt fan, $78 for a 66 watt fan and $160 for a 136 watt fan.

How many watts does a radon fan use?

RadonAway's RP series ranges from 17 to 21 watts for the RP140 up to 96 to 138 watts for the RP380. Most homes fall somewhere in between.

Can I put my radon fan on a timer?

No. The EPA says the fan should never be turned off; the system only works while it runs continuously.

Why is my radon fan's power draw higher than my neighbor's?

Fan choice and draw depend on soil, pipe length, suction points and sealing. Dense clay under a slab usually needs a stronger fan than gravel.

Does a radon system raise my heating and cooling bill?

Slightly. The EPA says most systems cause some loss of conditioned air. Good sealing keeps that small.

Where this information comes from

• U.S. Energy Information Administration, Electric Power Monthly Table 5.6.A, average residential price by state (August 2026)
• RadonAway, RP Pro Series radon fan performance and wattage table
• U.S. EPA, Consumer's Guide to Radon Reduction (2016 PDF)
• Angi, How Much Does Radon Mitigation Cost? (2026 data)
• U.S. EPA, Health Risk of Radon (lifetime risk chart, 21,000 deaths estimate)
• EPA Map of Radon Zones, county data (Rutherford County, TN: Zone 1)