What the Hell is the Difference Between a Kilowatt (kW) and a Kilowatt-hour (kWh)

Dan Hahn

Dave,

so let’s say I put in a 100 watt bulb, leave it on for two hours. My electric company here in Oregon is gonna charge me .20KwH? So that’s like two pennies? (.2 * $.09/KwH = $0.018)

David Llorens

yes

Joan

I have an oxygen generator which is rated 480Watts. 4.8 Amps. So if I run it for an hour am I using .48kW ? Trying to figure out how much electricity it uses in a 24 hour period. All help gratefully accepted. Thank you

Joan

If I have a machine rated 480W. does that mean it burns 0.48kW per hour?

David Llorens

yes sir!

Nick Walker

Can you convert a kilowatt to a kilowatt hour?

David Llorens

The are two different things. In the article it provides a good metaphor for thinking about the difference between the two.

A kilowatt hour is is one kilowatt of power for one hour of time.

Daniel

Two questions, So if an appliance has a surge rating of 5000 watts and a surge time of 5 seconds (5/3600 of an hour) is the power used 6.94 Wh [.00694 kWh]?

Are kWh or kW usage at a peak time more important when evaluating a solar or wind system capacity?

confused

If I have a machine that says 4.37kW/24 hours, does that mean its kilowatt or power rating is 4.37/24=0.182kW, ie, it consumes 0.182kW of power every hour? Thanks in advance

EDDY

M realy confused!!! Can some1 tell me if a turbine has an output of 120 KW, what does it mean? does it mean, that it ll produce 120 KW of power per hr?

Tom

Eddy check this link out.

Seems like your 120 KW turbine would produce about 210240 KWh a year which equates to about £21,000 worth of electricity (probably about $21,000 dollars to taking into account the differences in energy prices over here).

Tracies

How would I determine what size generator that can power my whole house, water well and central?

DJ

My power bill says I am using 3640 kwh per month, but the national average I found on the web is only 780 Kilowatts per month for a 2500 sq foot house..why am I so far over?

Dan Hahn

DJ,

That is a whole bunch of electricity per month. Are you propagating anything in your basement? If not (and you aren’t operating a theme park or live in a gigantic mansion), you might want to check your electric bill– again. Perhaps that was the amount you used in the past year.

DJ

Dan -
No, my current energy used since the last meter reading is 3640 kWh – the statement shows my daily averages as: Current Month 117; Last Month 126 and Last year as 133 – granted, I am in Arizona and therefore have two a/c/heatpump units on the home, we use these to “zone” the usage. However, we have solar panels to heat our water so I am still baffled at the amount I am using. I can tell from your reaction this is still as extreme as I was thinking. Do you think it would be worth my while to find an energy auditor to check my home out or do you think SRP (the power co) should do some explaining?

Dan Hahn

DJ,

How much did you pay for electricity last month? If you feel you’re using about as much electricity as your neighbors, I’d compare power bills. If they are similar, perhaps you could jointly approach the power company with a request for clarification. Otherwise, I’d definitely look into a home energy audit. Even if you aren’t hemorrhaging electricity (which I think you might be), your auditor will probably be able to show you how to save more in power expenses than the audit costs. Either way, you save.

Good luck and please give us an update. I’m sure you’re not the only one with a power bill like this.

Raveesh

why ups neutral cable is bigger(Guage) when compared to raw power neutral. please help me out to know this.

Jon

I have a 3500sq foot of living space above ground and a 1500sq foot of living space in the basement finished. I average about 3500kwh a month. Does this sound about right, I have 3 gas furnaces heating the home, 3 air conditioners during the summer cooling the home, and of course all the lights and tv’s throughout the house. In the mid of last summer my bill was Almost $600.00 for the month, is there a solar panel/wind turbine system out there big enough that can run my house using this much electricity and if so, how much would a system like this cost?

matt

how come power bills come as kwh instead of just kw?

SHAN

THIS IS THE ANSWER TO #4
ok. so kWh= kilowatts per hour used. a kilowat is 1000 watts, and a watt is a measurment of power.

Penny

Hi! My dad has a grinding machine.
Amperes: 180
Phases: 3/380 V
HP 75
Price of electricity per kwh: 2.84 rupees .
He wants to know how much electricity he pay for 1 hour? Can anyone help me,plz?

joe

if i have a hair dryer rated at 1200 watts, and i use it for 20 min a day how many kilowatt-hours is this per day?

[...] What the Hell is the Difference Between a Kilowatt (kW) and a Kilowatt-hour (kWh) [...]

[...] What the Hell is the Difference Between a Kilowatt (kW) and a Kilowatt-hour (kWh) [...]

Sam Harriman

Thanks for explaining this difficult concept Dave. Here’s a good excerpt from an article that John Hynes wrote for Renewable Energy World:

Capacity versus Energy

To learn how to compare technologies within a load factor category, one has to understand a number of terms and concepts, like the difference between capacity — measured in kilowatts (kW) or megawatts (MW) — and energy, measured in kilowatts-hours (kWh) or megawatt-hours (MWh). People often quote costs/kW when they are really talking about costs/kWh. Since these sound similar, they must be similar. Unfortunately, they are not.

Capacity for a power plant (kW or MW) is probably best explained with a highway analogy. A 10-lane highway is able to allow more cars to get from one point to another in a given time period when compared to a three-lane highway. Likewise, a 1,000 MW power plant has the ability to put more energy, or MWh, to the grid in a given time period than a 500 MW power plant. The size of the highway is analogous to the capacity, or MW rating, of the power plant. The number of cars that pass from one point to another on the highway during a given time period is analogous to the energy, or MWh, that the power plant delivers during the same time period.

So the more lanes on the highway, the more cars that can pass from one point to another in one hour. Therefore, the larger the power plant’s capacity, the more energy the plant can deliver to the grid in one hour.

Now that we understand the difference between capacity and energy, we can begin to compare the costs of one power plant to another.

Read the whole article here: http://www.renewableenergyworld.com/rea/news/article/2009/10/how-to-compare-power-generation-choices?cmpid=WNL-Friday-October30-2009

Joy King

Your explanation is wonderful, thank you! And thx to Sam Harriman too for his articulation on how capacity compares to generation….

[...] What the Hell is the Difference Between a Kilowatt (kW) and a Kilowatt-hour (kWh) [...]

confused

Can someone help me figure something out? In trying to understand how a sample solar estimate came up with the number of panels it would need. Ok, so a home wants to eliminate 587 Kwhs per month.
-Solar hours per day is 4.9 with the derate factored in.
-Panel/inverter AC CEC watts is 197.8 with inverter efficiency considered
-Kwh/mo/panel is 29
-# of panels required is 20

Ok for this particular type of panel brand…
-DC STC WATTS 4500 WATTS
-DC PTC WATTS 4142 WATTS
-AC CEC WATTS 3956 WATTS

Sooo, I’m confused because I thought the goal was to have only enough panels to power your house for the Kwh per one day of what you want to elimate. But it seems the number of panels are for a months worth of usage.

Can someone please explain this to me? Thanks!

MARK

PLEASE EXPLAIN THIS !
People often quote costs/kW when they are really talking about costs/kWh. Since these sound similar, they must be similar. Unfortunately, they are not.
WHAT IS THE DIFFERENCE THEN ?