3 Watts to Joules
Watts measure power and joules measure energy, so the answer depends on time. Here is what a 3 W device uses over each period.
3 J per second
Because 1 watt = 1 joule per second, 3 W delivers 3 J every second it runs.
- Per minute
- 180 J
- Per hour
- 10,800 J
- Per hour (kWh)
- 0.003 kWh
- Per day
- 259,200 J
3 watts to joules, explained
A watt is a rate: one watt means one joule of energy is used every second. So 3 watts means 3 joules per second. To get a total number of joules you multiply by how long the power runs.
For example, a 3 W device left on for one hour uses 3 × 3,600 = 10,800 J. Over a full day it uses 259,200 J. On an electricity bill, one hour of use is 0.003 kWh.
3 W draws about 5% of the power of an old-style 60 W incandescent bulb. One hour at 3 W consumes 0.003 kWh of electricity — about 0.045¢ at a US average residential rate of $0.15 per kWh.
joules = 3 W × time in secondsSmart speaker (idle/listening) (3 W)
Standard smart speakers draw roughly 3 watts of continuous standby power waiting for their activation phrase.
Electrical Power Comparison Scale
Need a different power or time? Use the interactive converter below for any combination.
3 W energy over time
| Time on | Energy (joules) |
|---|---|
| 1 second | 3 J |
| 1 minute | 180 J |
| 10 minutes | 1,800 J |
| 1 hour | 10,800 J |
| 6 hours | 64,800 J |
| 1 day | 259,200 J |
Convert any wattage and time
The full Watts to Joules converter handles W, kW, MW, any time unit, and the reverse joules→watts and time calculations.
FAQ: 3 watts
How many joules is 3 watts?
3 watts is not a fixed number of joules on its own — watts measure power and joules measure energy, so you need a time. A 3 W device uses 3 J every second, 10,800 J over one hour (0.003 kWh).
How do you convert 3 watts to joules?
Multiply 3 by the number of seconds the power runs. Joules = 3 × time in seconds. For one hour that is 3 × 3,600 = 10,800 J.
How much energy does a 3 W device use per hour?
A 3 W device running for one hour uses 10,800 J, which is 0.003 kWh on an electricity bill.