So, what the heck is a kilowatt hour?
When we buy gas, we are charged by the gallon. When we buy electricity, we are charged by the kilowatt-hour (kWh). So, when you use 1000 watts for 1 hour, that's a kilowatt-hour.
EXAMPLES
Window-Unit AC's
- Rated 1000 watts: run for one hour uses 1 kWh
- Rated 1500 watts: run for one hour uses 1.5 kWh
- Rated 500 watts: run for one hour uses 0.5 kWh
Ceiling Fan
- Rated 24 watts: run for one hour uses 0.024 kWh
Light Bulbs
- Rated 100 watts: run for 1 hour uses 0.1 kWh
- Rated 100 watts: run 24 hours per day for 30 days uses 72 kWh (0.1 kWh times 24 hours times 30 days)
LED lights (They use much less power and last much longer)
- Rated 6 watts: run for 1 hour uses 0.006 kWh
- Rated 6 watts: run 24 hours per day for 30 days uses 4.32 kWh (0.006 kWh times 24 hours times 30 days)
Simple math lets you easily calculate your needs.
Energy for your entertainment systems
Here is a very important item. Think of an LCD TV with a 40 inch view. The average energy consumption for this sized TV is 168 watts, or 0.168 kWh per hour. The LED TV's we tested were about 35% more efficient in energy use than LCD, and the plasma TV's used almost twice as much energy than LCD. When you consider your sustainable energy system for your community, don't forget the power needed to entertain your team. A tried and true (and inexpensive)
LCD TV with a DVD player offers a supply of entertainment limited only by the number of DVD's you can acquire. Gaming system too are an essential form of entertainment, and both DVD players and Gaming systems use a relatively small energy footprint for the value it provides.
Note that DVD players and gaming systems use only about 10-50 watts. My DVD player is rated at just 20 watts and uses 0.02 kWh. When you consider the energy required to create a sustainable home or community in terms of cooling and heating, this is such a small factor for energy usage and is comparable to just two 100-watt light bulbs. Entertainment is a very important factor to consider in that when the going gets tough, it offers relaxation and motivations for the next day.
Green Energy Systems for Music Production Systems
A small music system, without any visual interface, takes much less power, but also provides significant entertainment value. I also have an old Radio Shack 4 watt amplifier with speakers. When used with the DVD (CD) player, it only uses 0.024 kWh and provides a comparable entertainment source in music. If you use a hand-held MP3 player under its own power, music provided with this amplifier is rated at just 0.004 kWh, and the MP3 player can be charged later. Of course, I have a full fledged PA system too, and it uses up to 6,200 watts of power, so for live events, this system would require a significant amount of energy - 6.2 kWh - yikes!
Other Conversions: If your device lists amps instead of watts...
Watts is the measure of the rate of electrical use at any moment. For example, a laptop computer uses about 50 watts. If your device lists amps instead of watts, then just multiply the amps times the voltage to get the watts. For example:
2.5 amps x 120 volts = 300 watts
If you're outside North America, your country probably uses 220 to 240 volts instead of 120.
Understand the difference between watts and watt-hours:
* Watts is the rate of use at this instant.
* Watt-hours is the total energy used over time.
When you hear a question like "If some device uses 100 watts, period of time is that for?", the answer is "The device draws that amount of power for what ever period of time you use the device."
It's like asking "If the speedometer in my car says I'm going 35 miles an hour, what period of time is that for?" Again, it is not for any period of time. You're going 35 miles an hour at that instant and if your car goes that speed for an hour, you will have gone 35 miles.
When measuring the use of watts over a period of time, we use watt-hours, not watts. The way it works is, watts or kilowatts for the amount at a given instant, and watt-hours or kilowatt-hours for the amount over a period of time. If you have a system that can generate a maximum amount of kilowatts, then you have to make sure you don't overload your system by using more than that amount. It's like driving my old 61 Chevy truck - it has a maximum speed of 50 mph up hill and about 56 mph down hill, so I can't get anywhere 60 miles away in less than an hour.
Saving on your electric bill
Many companies and home owners can save from 20% to 90% per year in energy costs by simply changing to LED lighting. There are companies out there right now that are entirely in the business of reducing energy costs for businesses, and they always start with making the lighting solutions more cost effective.
Developing a Sustainable Energy System
The main purpose of this article is to provide guidelines for people thinking of creating sustainable communities and systems a resource to use for planning. The key thing we need to consider when creating a sustainable power source is "what is the maximum amount of kWh I need?" and "how much do I need to store?" For example, if you are getting your energy from the sun through solar panels, you can only collect your power for part of the day, and you need to store that power for night use. So, if you use most of your energy during the day and just some at night, you need to average the kWh needed, consider the maximum amount needed at any given time, and then create your energy generation and storage needs. As another example, if you are getting power from the flow of a stream, you have a constant source of energy and may be able to bypass any storage considerations.
A Sustainable Community's Energy Needs
Note that in 2009, the average cost of residential electricity was 12¢/kWh (DOE) in the U.S. In 2007, the average household used 936 kWh/mo. (DOE) and would pay about $112 per month for it based on the April 2009 average rate. This does not account for peak usage. In other words, if your average use is 936 kWh/mo., but the maximum use is 3,000 kW at any given moment, you have have a system in place to accommodate 3,000 kW, not 936 kW. In a sustainable environment, you may consider that creating a 1.5 kWh system instead of a 3.0 kWh system is much more reasonable, but you would have to make sure that usage never peaked past 1.5kW at any given time, or you could damage your system.
For example, if the entire community used 1 to 8 watt LED lights for navigating the work space safely (this is doable), this would significantly diminish the energy costs. Centralizing kitchen, heating and cooling facilities also diminishes costs. Having a community entertainment center is a no-brainer, with just a 0.2 kWh energy capacity needed to supply it. I will leave it to you to determine the details of the needs, but if you need help, feel free to contact me directly through
Graceful Expectations to help in your planning. - Teo
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