And what are the risks of not having it done?
The first thing to say about the cost of dryer vent cleaning is that the risks of not having your dryer vent cleaned could be much more costly. The US Fire Administration says that "2,900 home clothes dryer fires are reported each year," and of those fires, the leading cause is failure to clean the dryer. The reason is simple: as your clothes dryer works to dry your laundry, small bits of lint come loose from the fabric. Many of these end up in the lint trap, but some of them make their way into the ducting system, testimony of which is seen in the form of small bits of lint clinging to the outside vent. Each time you run your dryer, more lint is added to this accumulation and, unchecked, it can form a clog. Dryer lint is extremely combustible, and a dryer vent line clogged with lint is an accident waiting to happen.
The average cost of dryer vent cleaning.
Hiring a professional to clean your dryer vent will usually cost between $100 and $200, depending on a few factors. Do-it-yourself kits, consisting of a brush head and some flexible rods that fit onto the end of a drill, can be had for as little as $16, but unless your dryer vent is extremely straightforward (few turns, not too long, not exiting onto the roof, etc.), a professional service would be recommended to ensure a thorough job. The last thing you'd want to do with a DIY kit is compact the lint further but not be able to expel/remove it, causing even more of a fire hazard.
Factors that increase cost.
If you're lucky, your dryer has a short, straight vent line that goes right from the unit to the outside, on the first floor, in a matter of a few feet. But many dryers don't. The single condition that's almost guaranteed to cause you to have to pay more for the service is if your dryer vents onto the roof. For reasons of increased labor and increased risk/liability for the service company, these jobs are going to be more costly.
A long vent run—say, more than 15 or 20 feet—may also cost you more, as might a vent line with several twists and turns. Townhomes, for example, often have clothes dryers that are located near the center of the residence, requiring the vent line to extend tens of feet and several turns to reach a wall before venting outside. Simply speaking, any factor that makes the job more laborious, risky, or time-consuming will likely mean you'll pay more.
Still worth it.
In the grand scheme of things, at least within the realm of property ownership, the $100 or so you'll pay to have your dryer vent cleaned is well worth the peace of mind that you've greatly reduced your risk of house fire. Additionally, the increased air flow translates into energy efficiency and a lower utility bill, as well as shortened drying time for your laundry. A cost-benefit analysis would point to a pretty clear win for dryer vent cleaning.
Wanna dig deeper? Download our free tipsheet: 5 Questions to Ask Before Hiring a Dryer Vent Cleaning Company.