Cable length needed depends on the sizes and areas of the roof that need to be deiced (roof with gutter, downspouts, valleys, and/or dormers). Our best recommendation is for you to give us a call (1-800-875-5285) and we can help you identify what measurements will need to be taken. Alternatively, you can
measure the dimensions of the aforementioned areas and refer to the installation manual to get an idea of how much cable you'll need.