http://www.customs.gov.np/contents/Procedure/Passenger-Clearance/6/

For television sets, you can just use the following guidelines:

(For those who are returning back after spending more than 6 months abroad)
0″ – 22″ Rs 250 /inch
23″ – 29″ Rs 350 /inch
30″ – 32″ Rs 640 /inch
33″ – 39″ Rs 800 /inch
40″ – 49″ Rs 850 /inch
50″ – over Rs 1600 /inch

(For those who are returning back after spending less than 6 months abroad)
0″ – 22″ Rs 300 /inch
23″ – 29″ Rs 425 /inch
30″ – 32″ Rs 720 /inch
33″ – 39″ Rs 900 /inch
40″ – 49″ Rs 950 /inch
50″ – over Rs 1700 /inch

Bottom line is, it is stupid idea to take television sets with you as it is going to be very expensive.