20 sqft HeatTech 240V Electric Tile Radiant Floor Heating Mat Kit Mat size: 20" wide x 12.2ft long Voltage: 240V; Amps: 1A; Watts: 240W; Heating cable is only 1/8" thick and will not raise floors significantly. Cold lead: 10ft. Cable spacing: 3". System output: 12Watts per sq.ft (41 BTU/sq.ft); 240V mats can be combined to heat up to 300sq.ft. of space using a single thermostat. UL listed.