Frontdoor is the largest provider of home service plans in the United States, as measured by revenue, and operates under the American Home Shield, HSA, OneGuard and Landmark brands. Our home service plans help our customers maintain their homes and protect against costly and unexpected breakdowns of essential home systems and appliances. We maintain close and frequent contact with our customers as we respond to over four million homeowner service requests annually (or one every eight seconds on average) utilizing our nationwide network of over 16,000 pre-qualified professional contractor firms. Our value proposition to our professional contractor network is providing them access to our significant work volume, increasing their business activity while enhancing their ability to manage their financial and human capital resources. We realize significant economies of scale as a result of our volume of service requests and we intend to leverage our advanced customer and contractor-centric technology platform, expanding independent contractor network, existing customer base, purchasing power for replacement parts, appliances and home systems and extensive history and deep understanding of the home services market to generate sustained growth of our core home service plan business as well as to develop a new on-demand home services business.
We serve over two million customers annually across all 50 states and the District of Columbia. Our home service plan customers subscribe to a yearly service plan agreement that covers the repair or replacement of major components of up to 21 home systems and appliances, including electrical, plumbing, central HVAC systems, water heaters, refrigerators, dishwashers and ranges/ovens/cooktops. Product failures can pose significant emotional and financial challenges for our customers as these items tend to be the most critical and complicated items in a home. Given the potentially high cost of a major appliance or home system breakdown, the cumbersome process of vetting and hiring a qualified repair professional and, typically, the lack of formal guarantee for services performed, our customers place high value on the peace of mind, convenience, repair expertise and service guarantee our home service plans deliver. As homes become increasingly complex and connected, our ability to innovate, both through upgraded product offerings and through channel diversification, has allowed us to grow the home service plan category as well as our share of that category.
Our service plans appeal to the growing category of U.S. homeowners who seek financial protection against unexpected and expensive home repairs and/or the convenience of having a single home service provider that delivers pre-qualified, experienced professionals and service guarantees. Our multi-faceted value proposition resonates with a broad customer demographic, regardless of home price, income level, geographic location, or age. We acquire our customers through our partner real estate brokers and directly by advertising and marketing through our direct-to-consumer (“DTC”) channel. As a result of our strong customer value proposition, 66 percent of our revenue in 2018 was recurring, in line with historical averages, driving consistency and predictability in our revenues. In addition, a significant majority of our home service plan customers automatically renew on an annual basis.