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What’s the difference between kilowatt and kilowatt hour?

Kilowatt vs Kilowatt Hour

When using electricity in your home, you may never think about how many kilowatt hours (kWh) you are using to charge your __________(insert energy hogging device here).  But the reality is, every device you plug into an outlet or hard wire into your home uses electricity and those kilowatt hours eventually add up to what you pay monthly to the electric company. Being an energy consultant I am often asked, what is a kilowatt hour?

The easiest way to illustrate a kilowatt hour is to use the example of a 100 watt lightbulb:

One kilowatt hour of energy is equal to 1,000 watt hours or the equivalent of lighting a 100 watt light bulb for 10 hours.

(100 watts x 10 hours = 1,000 watt‐hours = 1 kWh).

Believe it or not, a kilowatt hour can go pretty far.  Here are some examples of a typical use of a single kWh:

‐ Watch television for 10 hours

‐ Wash 12 pounds of laundry

‐ Work on a laptop computer for 5‐10 hours

‐ Vacuum for one hour

Here are some examples to illustrate kilowatt hour consumption by common household devices:

Ceiling Fan: 0.075 kWh/hr.

Kilowatt hour

Kilowatt Hours Can Add Up!

Central Air Conditioning (3 ton‐12SEER): 3.0 kWh/hr.

Portable Heater (1500W): 1.5 kWh/hr.

Dishwasher, Normal Cycle – Cold Water 1.0: 2.17 kWh/load

Oven, Microwave: 0.12 kWh/5 min

Energy Star Refrigerator (frost‐free), 17 Cu/Ft: 73.0 kWh/mo

Electric Iron: 1.0 kWh/hr.

Television >50” Plasma: 0.48 kWh/hr.

Television > 50" LCD: 0.22 kWh/hr.

Recording Device – DVR: 28.8 kWh/mo+ depending on the model

Computer – Laptop: 0.02 ‐ 0.05 kWh/hr.

iPhone 6:  3.8 kWh/per full year! (4.2 kWh iPhone 6+)

Golf Cart Batteries (48 Volt) - New: 2.8 kWh/per full charge (up to 10 kWh on old batteries)

Tesla Model S (P85D): 85 kWh/per full charge (3,400 Kwh per year assuming 12,000 miles driven)

When considering solar for your home, it's helpful to understand the amount of energy the devices you plug in and use everyday contribute to your monthly electric bill. Energy efficiency is a powerful way to save money in the short term (by lowering your electric bill immediately) and in the long term (by lowering the cost of your solar system since you'll need fewer panels to offset your usage).