Electric Power is the rate at which work is done. (See also: What is Work, Energy and Power?) Electric Power is the rate at which electricity does work or provides energy. The SI unit of power is the watt, one joule per second.

Electric power is usually produced by electric generators, but can also be supplied by electric batteries. Electric power is usually sold by electric companies as the kilowatt hour (3.6 MJ) which is the product of power in kilowatts multiplied by running time in hours. Electric utilities measure power using an electricity meter, which keeps a running total of the electric energy delivered to a customer.

**Definition and Equations for Power**

Electric power, is the rate of doing work, measured in watts, and represented by the letter P. The term wattage is used to mean "electric power in watts." The electric power in watts produced by an electric current I consisting of a charge of Q coulombs every t seconds passing through an electric potential (voltage) difference of V is:

P = work done per unit of time = VQ/t = (V)(I) or Power = Voltage x Current or Volts x Amperes

where: Q is electric charge in coulombs, t is time in seconds, I is electric current in amperes and V is electric potential or voltage in volts

**Electric Energy**

Electrical Energy = Power x Time. The total amount of electrical energy used depends on the total power used by all your electrical devices and the total time they are used in your home.

__Electical Energy is measured in kilowatt-hours__

Energy =Power x Time or Kilowatt-hours = Kilowatts x Hours

One kilowatt hour is equal to 1000 watts of power used for one hour of time.

**How to calcuate cost of electricity**

__From Con Ed Bill__ --"We measure yur electricty by how many kilowatt hours ((kWh) you use. One kWh will light a 100 watt bulb for 10 hours". "In 2015, the average annual electricity consumption for a U.S. residential utility customer was 10,812 kilowatthours (kWh), an average of__ 901 kWh per month__. Louisiana had the highest annual electricity consumption at 15,435 kWh per residential customer, and Hawaii had the lowest at 6,166 kWh per residential customer."

__SAMPLE PROBLEM: __

How much energy and power will it take to run a 900 watt air-conditioner for 10 hours straight?

__Solution: __Energy = Power x Time = 900 watts x 10 hrs = 9000 watt-hours = **9 kWh.**

**DATA FROM A 2017 NYC CON ED BILL**

A lot goes into understading what you are paying for. There is not just a cost for fuel but also delivery charges and fees for various services and taxes.

To help explain this we use an Actual Con Ed Bill for a small apartment in New York City Using Con Edison.

**From Con Edison: **

Electricity you used during this 30 day billing period fro Jan03 2013 to feb 02,2017

We measure your electricity by how many kilowatt hours (kWh) you use.

One kWh will light a 100 watt bulb for 10 hours.

February 02,17 actual reading 95175 kWh

Jan 03 , 17 actual reading 94838 kWh

Your electricity use was therefore** 337 kWh**

Merchant function charge - charge associated with procuring electricity credit and collection related activities = $1.41

__GRT and other taxes = $0.48__

**Total Supply charges = $20.52** which comes to 6.1 cents/per kWh.

Basic service charge** $16.38**

This is the change for basic system infrastructure and customer related services, including customer accounting, meter reading and meter maintenance.

**Delivery 337 kWh @11.0208 c/kWh = $37.14 **

This is the charge for maintaining the system through which Con ed delivers electricity to you.

**System Benefit Change at 0.6706 c/kWh = $2.26**

This recovers costs associated with clean energy activities by New York STate Energy Research Associate

**Temporary NY State Surcharge 0.1246c/kWh =0.42**

Covers new fees imposed by the state

__GRT and other surcharges $2.87__

**Total delivery charges $69.5**

__YOUR SALES TAX @4.5000% collected on behalf of NY State = $3.58__

**YOUR TOTAL ELECTRICITY CHARGES IS $63.15**

__SAMPLE QUESTION: __

What is the supply charge to run a 600 watt refrigerator for 24 hours (of ON usage) at a cost of 0.06 cents/kWh? Note: Refrigerators do not run continuously.

Solution: Energy = Power x Time = 600 watts x 24 hours = 14,4 kWh x 0.06 cents/kWh = 864 cents = **$8.64**

- Electricity and Magnetism Home
- Electric Charge
- Coulombs Law and Inverse Square Law
- Static Electricity
- The Flow of Electricity
- Electric Current
- Electric Circuits
- Electric Power
- The Nature of Magnets
- Earth as a Magnet
- Magnetism in Action
- Magnetism from Electricity
- Electricity from Magnetism
- How do Transformers Work?
- Ohms Law Lab
- Magnetic Forces Lab
- Why Metals Conduct Electricity
- How does a Battery Work
- How does an Electric Motor Work

- Science of Fluids
- What are Fluids?
- What is Pressure?
- What is Hydrostatic Pressure?
- Surface Tension and Capillary Action
- Pascals Principle
- Archimedes Principle
- What is Viscosity?
- Bernouili's Principle