Minimally. The fan runs continuously and uses about 50-90 watts, roughly $5-$10 per month in electricity. Heated/cooled air loss through the system is offset by sealing work done during install.
More detail
The math: a Radonaway RP145 fan at 80 watts running 24/7 consumes about 700 kWh/year, costing roughly $90-$110/year on Duke Energy Cincinnati residential rates. The conditioned-air loss through the radon stack is typically a wash because the install includes sealing slab cracks, sump pits, and rim-joist penetrations that were leaking conditioned air into the soil before mitigation. In practice, blower-door tests pre and post often show a slight reduction in air-change rate after mitigation due to the sealing work. For homes with combustion appliances (gas furnace, water heater, gas dryer), proper mitigation design includes makeup-air consideration; back-drafting is preventable but worth confirming with a combustion-safety test if the home uses natural-draft appliances. Cincinnati Duke Energy residential rate context: at roughly $0.13/kWh average and 700 kWh/year fan consumption, the annual electric cost runs $90-$110. Time-of-use plans (off-peak overnight charging) do not affect this materially because the fan runs continuously. Solar-equipped Cincinnati homes effectively offset the full radon-fan electric cost; battery-backed solar covers it during outages too. For homeowners tracking energy use closely, the radon fan is a fixed continuous load that shows up cleanly on smart-meter usage breakdowns and can be verified at install time using a Kill A Watt meter or equivalent.