Watts & Kilowatts & kWh… Oh My!
We’ve all looked at a lightbulb and have noticed that it says, “100 Watts,” but what does that mean? We’ve also looked at our utility bill and seen that we’ve been charged for the amount of Kilowatt-hours (kWh) we’ve used. But, again, what does this all mean? These terms are often used incorrectly and interchangeably, so we thought it was time for a clear explanation of what these units are and what they mean.
Let’s start with the basics. A watt (W) is a measure of POWER (or one joule per second). Power is the rate at which energy is used per unit time (an indicator of how fast an item uses energy). A kilowatt (kW) is, simply, one thousand watts, just as a megawatt (mW) is one million watts. When we’re talking about electricity, power is voltage times amperage or 1watt = 1volt x 1ampere.
True, this may sound a bit like your high school physics class, but don’t panic. Read on and you’ll see it’s a simple concept to grasp…
One of the easiest ways to think about all of this is to think of electricity as water coming out of a hose. Voltage is the water pressure and the amperage is the flow. When there’s a kink in your garden hose, there’s a lot of pressure (voltage), but the water is not flowing anywhere (no amperage), which means there’s no power (i.e. a lot of volts x zero amps = zero watts).
Now let’s take this understanding and apply it to what happens when we un-kink the hose, and the water comes rushing out of it. The result is, a lot of volts x a lot of amps = huge POWER.
Okay, so you’ve got the concept POWER down, let’s go back to Watts (W). A Watt (W) is energy burned per second. A 100-Watt light bulb eats up 100 Joules of energy every second. Since “Watts per hour” doesn’t make sense, because it’s already measuring “Joules per second” and thinking of “Joules per second per hour” is enough to make most people’s eye glaze over, our utility companies use a Watt-hour to charge us for the electricity we use. It’s a way of removing “per second” from Watts.
Now let’s use one more analogy to wrap up this explanation, pretend you’re running a marathon. Think of Watts as the speed you’re running (i.e. the rate of energy used in that instant), and Watt-hours as total amount of energy you’ve used while running at a certain rate over an hour.
A Kilowatt-hour (kWh) is the amount energy equivalent to power one kilowatt (kW) for one hour. A kilowatt hour (kWh) is a unit of ENERGY that is a much more convenient unit of energy to use rather than the kilo-Joule. It represents the power used by the appliance multiplied by the hours in use. In other words, when you leave a 100-Watt light bulb on for 10 hours you’ve used a kilowatt-hour (kWh) of energy and TEP will bill you accordingly.
So, as you can see, the kW and kWh are fundamentally different. Appliances show their power ratings (kW) on the nameplate to give you an idea of how much energy is used per second by the item. At TFS, we look at the amount of kWh on your utility bill to find out how much energy your home or business uses so that we can recommend what size solar PV system would best suit your needs.
Survey Shows More Americans Support Solar Energy
Solar energy is getting the positive attention and widespread acceptance it deserves. A recent study, from Rasmussen reports (a comprehensive public opinion poll), showed that 44% of Americans believe in investing in solar for their home. According to the survey, nearly one-out-of-three adults (31%) say they are at least somewhat likely to use solar power in their homes in the next five years, including 13% who say they are very likely to do so.
Interestingly, the survey also found that 55% of voters believe finding new sources of energy is more important than reducing the amount of energy Americans now consume. Also notable, is the age of those who are willing to forge a solar path. Supporters in the 18 to 40 age brackets feel solar energy will become a standard method of powering their homes. Moreover, those in this younger age group are also roughly twice as likely as to say they are very likely to use solar power in their homes in the next five years.
The survey also made it clear that there is still the misconception that solar is financially out of reach for the mainstream. For example, 25% of those making more than $100,000 per year said they are very likely to install solar power at home in the next five years, compared to only 6 percent of those making between $20,000 and $40,000 per year.
There also seems to be a perception that the payback needs to be faster (in the three to five year range), before solar technology is widely adopted by the mainstream. It will be fantastic when prices get down to that level, but when looked at honestly, anything less than a 20 year simple payback provides a good investment. But, the great news is that the average payback for a residential solar PV system is about seven to nine years. However, for the sake of making a point, a solar system that provides a 20 year simple payback is like buying a solar bond that pays 5% (tax-free) interest year after year without ANY risk.
Think of it as buying your own dividend-paying utility company, but one with a long operating history and no competition. Current tax credits and utility rebates cover up to 70% of the total cost of the solar PV system. Also, there are financing programs (or call 1-800 sunpower) to help Southern Arizona’s homeowners make the switch to clean energy.
It is nice to see evidence that American support for solar energy is continuing its upward swing. This new survey provides credible proof of the positive trend among the American people, in considering the switch from coal to clean energy from the sun.
Solar Continues to Shine Bright
Solar continues to Shine Bright in SEIA’s 2009 Year in Review
Once again, we are seeing proof that an economic recession can’t stop the sun from shining in, according to the Solar Energy Industries Association (SEIA). They recently released the 2009 U.S. Solar Industry Year in Review, which reports on the health of the solar industry. They found that the US solar industry experienced significant growth last. Overall, the US experienced a 36% improvement over last year. We are ranked 4th in new solar capacity worldwide with industry growth totaling nearly $4 billion. This 37% increase was mainly the result of an ever increasing demand for residential PV installation and utility-scale installations
“Building off the successes of 2009, we expect 2010 to be a breakout year for the U.S. solar industry,” said Rhone Resch, SEIA president and CEO. “The right policies and industry innovation continue to drive solar’s growth across America. Now we’re talking gigawatts of solar, not megawatts.”
Highlights for 2009 include:
Growth in added solar electric and solar thermal capacity
· Solar electric capacity growth (including both photovoltaic and concentrating solar power technologies) for 2009 was 37 percent more than 2008.
· Solar water heating grew by 10 percent over 2008
Jobs and Revenue
· The solar industry contributed to the overall economy by adding 17,000 new jobs.
· Solar industry today supports 46,000 U.S. jobs and supports an additional 33,000 jobs in other sectors.
· Growth in the industry resulted in a 36 percent increase in overall revenue, totaling nearly $4 billion.
Increased capacity by solar technology
· Photovoltaic installations (grid-tied) grew by 38 percent
· Solar water heating grew by 10 percent annual over 2008.
Capacity by market segment
· Residential grid-tied PV solar installations showed particularly strong growth, doubling from 78 megawatts to 156 megawatts.
· Non-residential grid-tied PV solar installations grew 2 percent less than in 2008.
· The utility market saw notable growth, with utilities tripling their rate of grid-tied PV capacity additions from 22 megawatts to 66 megawatts
· California has continued to lead the way using 220 MW in solar energy capacity, with Arizona ranked 4th using (23 MW), behind New Jersey (57MW), and Florida (36 MW).
Good news for solar means good news for the economy, as well. As more homeowners install solar power, more jobs are created. For every six homes that go solar, one local green job is created. By the end of the year, the US is expected to have 60,000 solar supported jobs. The growth of the solar power market in closely connected to our economic health as a country.
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