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

By: Chuck

Chuck — Tue, 27 Mar 2012 00:21:11 +0000

Okay, so then the bulb is already rated at how many watts it will use in an hour? Meaning if I’m using a 3 watt LED it will only consume 3 watts of energy over 60 minutes worth of time and therefore it’s watt-hour rating is 3?

I’m desperately trying to understand this so I con’t get out in the back country and run out of power halfway through the evening and am stuck until the sun comes up to kiss my solar cells in the morning.

By: Ian

Ian — Fri, 23 Sep 2011 14:36:10 +0000

I THINK (please correct me if I am wrong) but if a solar system had 10 200 watt panels and peak solar sun time averaged 5 hours per day AND the inverter and the panels were able to actually OPERATE at the rated output of 2KW (10×200watt panels) then with 5hours per day of Solar sun the system would produce 10KWh (killowat HOURS) of energy available during that time. ALSO if during that day the power is produced then NO power in EXCESS of the hourly draw of 2KW could be drawn from the system. Is this right please?

By: Ray

Ray — Fri, 25 Feb 2011 00:36:57 +0000

I have an aquarium pump with a 70 watt capacity. I have a solar panel which outputs 17 volts dc and can charge a 12 volt car battery nicely. If I get an inverter, connect it to the battery charged by the solar panel will it run my pump 24 hours. I live in the Philippines so sun is no problem.

By: suhas

suhas — Fri, 04 Feb 2011 06:50:41 +0000

i have 30 incandescent bulbs of 60w each . show me calculation for kilowatts of energy used

By: Akinwumi

Akinwumi — Wed, 12 Jan 2011 19:47:39 +0000

Love dis site very much

By: MARK

MARK — Mon, 26 Jul 2010 13:39:47 +0000

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 ?

By: confused

confused — Tue, 29 Jun 2010 15:42:26 +0000

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!

By: Detroit Rocks for Solar Power Incentives

Detroit Rocks for Solar Power Incentives — Sun, 17 Jan 2010 21:57:52 +0000

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

By: Joy King

Joy King — Sat, 02 Jan 2010 01:57:10 +0000

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

By: Sam Harriman

Sam Harriman — Fri, 30 Oct 2009 17:53:41 +0000

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