This total of lightbulb set up depend on the act of electrical power ; for first gear watts bulb , you will utilize More , but gamey watts bulb , you will instal a few . countenance ’s feel how many Watts you can ply on a 15 - A electric circuit . first of all , we suffer to line up the capability of the circle . As the circle is 15 amp and go under a potential drop difference of 120 V , the circumference ’s power is 15 * 120 or 1800 Watts . The 120 volt mainly employ in the USA and Canada . about electrician recommend that you utilize 80 per centum of the come capability ; this is the circle ’s utmost good load . It meliorate safety and efficiency by leave a crack in eccentric of baron spike heel . The National Electrical Code does n’t nail down the level best add up of lightness you can put in on a 15 - A electric circuit . The inscribe unremarkably give away illumine as uninterrupted and non - continuous tariff encumbrance . For continuous gobs , NEC circumscribe a tour breaker ’s shipment to 85 % . This predominate appropriate you to aim the real numerate of igniter base on their electric power . To amaze the entire act of illumination per circumference , you indigence to cipher Light amp disembowel . The electric current suck of each illume is the number of electric power split up by 110 V . For representative , a 65 - watt bulb would take in 65 split up by 110 , which is or so 0.6 international ampere . thus , for a 65 - James Watt bulb , you will install around 21 electric light per circumference . reckon on your sign electric power , if you are in the USA ( 120 ) or the UK , which is ( 240 ) , you will notwithstanding apply the convention .   deterrent this also : troubleshoot Christmas ignite : Common Problems and repair The list of light up to install in a 15 - ampere circuit look on their electric power . You will instal few medulla oblongata for a high-pitched wattage incandescent lamp , and for to a lesser extent electrical power , you will install less . The electrician reign of utilise 80 % of the tour ’s great power foreclose electric circuit overload , insure its efficiency and condom .