Power Calculations
After sorting the devices from the power company, we saw that power (how fast a device uses energy) and time (how often you use it for) both matter in terms of cost. This is because the power company bills you for how much energy you use. A quick rearrangement of the power equation lets you solve for energy.
In calculating cost to use a device in the United States, we don't get the energy use in Joules (J), but instead in the strange unit of kilowatt hours (kwh). The math to convert is shown here.
Once you know your kwh for each device, you multiply by the current rate your power company charges. The 9.08¢ rate was what Eversource was charging CT customers as of 2018-03-01.
Note the light bulb, despite being much lower power (it uses energy much slower) costs more to run each month than the toaster. It's used more.
Values for energy use from Cornhusker Power Company
Power Calculations
After sorting the devices from the power company, we saw that power (how fast a device uses energy) and time (how often you use it for) both matter in terms of cost. This is because the power company bills you for how much energy you use. A quick rearrangement of the power equation lets you solve for energy.
In calculating cost to use a device in the United States, we don't get the energy use in Joules (J), but instead in the strange unit of kilowatt hours (kwh). The math to convert is shown here.
Once you know your kwh for each device, you multiply by the current rate your power company charges. The 9.08¢ rate was what Eversource was charging CT customers as of 2018-03-01.
Note the light bulb, despite being much lower power (it uses energy much slower) costs more to run each month than the toaster. It's used more.
Values for energy use from Cornhusker Power Company