To answer this question a voltage must be given.
A 0 Watt bulb does not consume electric power so the cost is zero.
current consumtion of a bulb
A 60 watt bulb at 12 volts will pull 5 amps of current.
That depends on the type of bulb AND on it's power usage. An old incandescent bulb of 100 watts uses about an amp, a 60 watt uses about a half amp. But a florescent bulb putting out the same light would consume about half the current, and a LED bulb would use less than half that.
It depends how much you pay for electricity. A 15 Watt bulb would consume around 134 kWh of electricity. In the UK, electricity is around 10p a kWh, so it would cost £13.40 to run the bulb.
A 240 v 14 w cfl bulb uses about 0.14 amps.
60 watt-hrs= 60 watt*1 hr so it will take 1 hour.
It's 75/120 and the answer is in amps.
A 50 watt bulb designed to run on 12 volts takes 4.17 amps. A 50 watt bulb designed to run on 230 volts takes 0.217 amps.
energy consume by the bulb = P*time =100*6 wh =.6 kwhour=0.6 unit energy consume by the bulb = P*time =100*6 wh =.6 kwhour=0.6 unit
There are about 8760 hours in a year, so running a 60 watt bulb for a year would consume (60 times 8760) or 526000 watt hours. Electric power rates vary, but at $0.15 per kilowatt-hour, that would be almost $80.
As long as the lamp holder will take the larger wattage lamp and the current of the circuit is sized to take the larger current then yes, the lamps should be interchangeable.