In 1500 Watts there are 12.5 amps at 120 volts.
If you have an appliance that is drawing 1500 watts at 120 volts then the 1500 watt appliance is drawing 12.5 amps.
For example if you have a 1500 watt space heater then your 1500 watt space heater will draw up to 12.5 amps so you need to make sure you have enough amperage capacity to supply the 1500 watt heater or appliance.
A 1500 watt appliance or electrical device should be on a dedicated circuit or at least on a circuit without anything else.
Remember the equation watts = volts*amps. If you have a 1,500W heater at 120V, it is using 12.5amps (1,500/120=12.5).
Alternatively, if you have a 1,500W heater at 240V, it is using 6.25amps (1,500/240=6.25).
A 1500 watt space heater (on high setting) will draw 12.5 Amps.
When a few lights or a television are on the same circuit, the 15 Amp limit is quickly reached and the breaker will trip.
A 1500-watt heater on a 120-volt circuit thus needs a breaker of 15.6 amps.
Because a 15-amp breaker would be too small, you need a breaker with the next highest rating, which is 20 amps.
A 1500 watt heater uses exactly this, 1500 watts per hour, relative to 24 hours, heating a modest-sized room.
Many household products use just as much if not more than 1500 watts, so, relatively speaking, heaters are fairly reasonable in terms of energy required.