BY GREENTUMBLE
If your community is like many others today, you’re seeing more and more solar panels installed on your neighbors’ rooftops. Solar photovoltaic system installations are booming.
If you’re starting to think about saving money on your electricity bill with clean solar energy, you’re probably wondering, “How many solar panels do I actually need for my house?”.
How much money can a solar roof save you ?
Profit from your roof space: find local deals on solar in your area, eliminate your power bill.
The first step in finding out the size of a solar system that will generate
enough power to meet your energy consumption is to calculate the amount
of electricity you use as this can vary a lot from household to household.
As an example, let’s assume two families live next door to each other in
1,000 sq. ft. homes.
A single guy lives in Home A and he often spends evenings out in the city
with friends or looking for his soul mate. Being alone, and most of the day out, he doesn’t use much electricity and pays about $50 a month.
In Home B, two parents live with a teenage kid. They are using the heater or
air conditioner often during the day and use electricity to filter their swimming pool, meanwhile the teenager is always on his iPad or watching TV. Since more people are living in the house and their way of life requires more energy, they pay $200 a month on electricity.
So even though the houses have the same size, the family in Home B would need to consider installing more solar panels to make up for their electricity usage than the single guy in Home A.
In your case you can think of it like this: The more energy your home uses,
the more energy has to be produced by your solar PV system.
Therefore, the more solar panels you are going to need.
How much solar power will you need?
To find out your average energy usage, check your past utility bills.
More precisely the last 12 months of your bills (so you include summer and winter months as energy consumption varies throughout the year). Look for the total number of kilowatt-hours (kWh) you consumed every month.
Sum the numbers up and divide them by 12 to get the average.
Calculate Energy Consumption
An easier way to determine your total energy consumption for the past year
is to simply call your utility company and ask them to provide you the details.
Based on the data available from the U.S Energy Information Administration, in 2013 the average family home in the United States consumed about 900 KWh of electricity per month. That’s 30 kWh per day.
Obviously your household can consume more or less electricity depending
on how big your house is, how many family members live in it, the appliances you have and how energy efficient you are.
How many kWh can solar panels produce and
how many panels do you need on your roof?
The amount of power (kWh) your solar energy system can produce depends
on the number of solar panels that can absorb solar energy and convert it into electricity.
Assuming you are going to choose standard-efficiency solar panels,
here are the most common sizes for residential solar systems and their kWh production potential to give you an idea of how many panels you would need
to run a house.
A 3kW solar system which consists of 12 panels can produce an average
of 4,200 kWh per year. You will need a roof space of about 194 sq. ft.
for a 3kW system.
A 5kW solar system which consists of 20 panels can produce an average
of 7,000 kWh per year. You will need a roof space of about 340 sq. ft.
for a 5kW system.
A 10kW solar system which consists of 40 panels can produce an average
of 14,000 kWh per year. You will need a roof space of about 680 sq. ft.
for a 10kW system.
Keep in mind that the amount of power your solar system can produce
depends on how much sunlight your roof receives and your location.
For example, California has more sunny days annually than Washington.
In this case if you live in Washington you would need a bigger solar system
to get the same power as you would get with a smaller system in California.
The Renewable Resource Data Center provides average daily total solar resource information on grid cells by state and it’s free…so check it out.
Further reading: What Questions to Ask When Buying Solar Panels
Few things about solar panel output efficiency
Solar panel type and quality make a significant difference in terms of solar output and efficiency. Not all solar panels are the same.
For instance, monocrystalline photovoltaic (PV) solar panels are known to be the most efficient solar panels on the market, but also the most expensive.
Their two main advantages over the other types of solar panels such as polycrystalline or thin film panels is that 1) they absorb more sunlight than conventional cells and their output efficiency is not affected that much by temperature and 2) they occupy less space.
These are an ideal option if you do not have enough roof space for standard (polycrystalline) panels.
On the other hand, polycrystalline panels are cheaper, they are less efficient and therefore occupy more space, but offer a better return on investment than monocrystalline panels.
Because of these wide differences in quality and efficiency, it’s up to you to decide which solar panels are right for your home.
The main takeaway is that, the more efficient the panels are, the more power they can produce, and the fewer photovoltaic panels you will need on your roof to get the same energy output as you would get with polycrystalline or thin film solar panels.
Overall, if money is not an issue, monocrystalline panels are the best option.
How much energy do you want to offset with solar?
Typically most people want to offset as close as possible to 100 percent
of their consumption. However, not everyone can afford to offset all energy consumption with a stand-alone solar system as the overall cost of the full home solar power system and its installation can get quite expensive.
Small solar systems on house rooftops!
Installing a smaller system and participating in the net metering program
is still a great way to reduce your electricity bill up to 50 percent or more.
How does net metering work?
Let us assume that you are gone on a vacation with your family.
The solar system still generates energy when you’re gone but since you are not using it, it’s being automatically sent back to the grid and you get credits for it. As a result, your electricity bill will decrease according to how many credits you have.
Knowing the answers to the above questions will give you an understanding of the number of panels needed to achieve your daily energy production goals and will allow you to calculate in a realistic range solar panels needed for your home.
Bottom line: I heard the average conversion cost for a house
is between $65,000 and $80,000.00.
Further reading: Best Ways to Finance Solar Panels
The efficiency of fossil fuels lies between 40 to 50% (around 42% for coal, 45% for oil & 52% for natural gas). Alternatively, the efficiency of solar panels range from 11 to 15% which is quite low. So, we can say that fossil fuels are highly efficient compared to solar energy.
How efficient is solar power to fossil fuels.
When reading up on solar panels, you’ll probably bump into the term “efficiency.” Although it sounds like a good thing, most people don’t exactly know what this term is. How efficient are solar panels? How do you even measure this?
In this article, we’ll analyze the factors that influence the performance of
solar panels in detail – solar panel efficiency. Moreover, we’ll also go over the environmental factors that detract from it. With silicon-based panels being the most common type today, we’ll specifically cover the efficiency of this material.
WHAT EXACTLY IS THE EFFICIENCY OF SOLAR PANELS?
In simple terms, this is a measurement that determines the amount of sun’s energy a particular panel is capable of converting into electricity. A solar panel converts the sun’s energy into electricity by capturing the current that’s generated when sunshine interacts with the panel’s thin film or silicon cells.
Typically, the cells are arranged into glass rectangles and are packed tightly. This is so that they can attract sunlight. Once the energy is converted, it is sent to the user’s circuit box. From there, it is distributed to the rest of the house.
How is this measured? If a particular panel has 15% efficiency, it can convert 15% of the sunshine that’s interacting with it into electricity. The models with the highest efficiency are capable of reaching 23% efficiency.
However, the average efficiency stands in the range of 15%-18%.
WHICH FACTORS AFFECT SOLAR PANEL EFFICIENCY?
The performance of these products is affected by a whole host of variables. Here are the most vital ones:
THE TYPE:
As they’re based on the silicon of highest purity, monocrystalline panels sport the highest efficiency. The polycrystalline models don’t perform so well, but they still do the job. Finally, the thin-film models are somewhat inefficient,
but they come at a low price. They do, however, take a lot of space, which makes them inadequate for most households.
MAINTENANCE:
In most cases, a solar system won’t require much maintenance.
This is especially true in case it’s grid-tied. Nevertheless, one should clean his system regularly. This is because dirt, dust, and other debris can easily affect the panel’s performance. Using soapy water is usually more than enough.
The rainfall can also do the job.
Those who are afraid of heights can use the cleaning services.
Unfortunately, there’s no single answer to the question of how often should one clean his panels. To get the idea of how frequently you should wipe off the dust and dirt, you can simply monitor the power output.
TEMPERATURE:
Unless you live in an excessively hot area (such as Phoenix or San Antonio),
the temperature is not something you should worry about. Typically, the efficiency of a particular solar panel will decrease as the temperature increases. To combat this, most professional installers position the panels in a way for them to receive an adequate amount of airflow.
This keeps the efficiency rates up by providing natural cooling.
ORIENTATION:
Another important factor is the orientation. To achieve the best performance, one needs to position his system in a way that maximizes the sunlight input.
In the case of the U.S., this means that the panels need to be faced southward. To make solar panel orientation easier, one can use trackers. These devices make the panel follow the sun’s trajectory. However, solar trackers are too expensive for most homeowners, and they don’t pass a cost-benefit analysis. The more straightforward solution would be to use racks to alter the pitch of the roof. In most cases, this is more than enough to allow your system to spend more time in sunlight.
SHADE:
This one is a no-brainer. Depending on one’s setup, shade can even
bring down the whole system. To prevent this from happening, one needs to consult professional solar panel installers. These experts conduct a thorough analysis of shading in one’s specific situation.
LIFETIME:
Like most other products, the performance of solar panels goes down with time. In most cases, this means a decrease in the power output of 0.5% with each passing year. Most companies back their models with warranties that guarantee that the performance won’t go below 25% after 25 years of use.
Read here to learn how long solar panels last.
IS IT TRUE THAT BAD WEATHER CAN DECREASE SOLAR PANEL EFFICIENCY?
One of the most common misconceptions surrounding the solar panel efficiency is that bad weather can lead to reduced performance.
However, the opposite is often true. Although designed to withstand average temperatures, these devices actually perform better when they’re cooler.
They need light, not heat – some of the most productive days are usually
bright winter days. Another thing people are often confused about is snow.
There’s nothing to worry about – a thin layer of snow doesn’t affect the performance as much as you think it does.
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This Is Why We Don’t Have Solar-Powered Cars
Elizabeth Blackstock.
Using the sun’s energy to power green vehicles seems like a no-brainer.
There’s a lot of sunlight in this world—why not harness it in order to
reduce our dependence on both fossil fuels and the electrical grid?
Well, the main problem is, it’s not as easy as you think.
There are a few solar concepts out there.
We have the Batmobile-esque Aptera, which has been evolving for over half
a century and will be released this year, the company says—though the solar power can only get you about 40 miles on a clear day. There’s the Lightyear One, a luxury sedan that integrates solar panels onto its hood and is said to
get up to 500 miles on a charge.
There was the C-MAX Solar Energi Concept, designed in a partnership
between Ford and Georgia Tech. Instead of needing to be plugged into an electrical grid to charge, its battery would have been fed by solar power.
There’s also a Formula SAE program that’s designed around building a
solar-powered car.
But if you’ve ever been wondering why solar-powered EVs just haven’t
caught on, Jason Fenske over at Engineering Explained is here with a whiteboard full of math to tell you exactly what you need to know about
what makes this prospect so challenging.
I’m not the kind of person who’s going to be able to explain math to you in a way that makes sense—you’ll have to watch Fenske’s videos for those details. What I can do, however, is paint a few broad strokes to give you the overview you need.
Basically, to harness the 173 trillion kilowatts of power that hit the Earth at any given second is no easy task. The small size of a car can only harness about 12 kilowatts of that power, but that translates to about 62 mph when you convert that power into speed—and you could travel 62 mph indefinitely, as long as the sun is out. In those same ideal circumstances, you could also charge a 75 kW battery in just over six hours. Not bad, right?
That’s because those numbers are in a perfect world, which is not the world we live in. Sunlight is reflected back into the atmosphere. It’s dulled by clouds and tall buildings. And the Earth is curved, so some parts of the planet are going to get more sun than others. And Fenske’s example car was entirely covered in solar panels; in his next calculations, he factored in windows and glass.
Now, instead of 12 kilowatts of power, only 0.375 kW are hitting the solar panels. That translates to a constant speed of 19 mph under pretty ideal conditions. It also means it would take over eight days to charge your battery. And that’s only if you’re not using it.
That’s not ideal. It’s not even really worthwhile to slap a solar panel on there to try to absorb some extra power, since that power would be incredibly minimal. It would be the equivalent of putting a batch of cookies out in the weak sunshine on the off chance they might get cooked a little bit.
Once again, it all comes down to efficiency. In the future, solar panels may
be more efficient, but right now, we’d be depending on a pretty finicky natural resource whose ideal performance could only be achieved at a certain location at a certain time of day during a certain time of year and under certain weather conditions. That’s not exactly something you want to rely on for your daily commute. Why Don’t Solar Powered Cars Exist?
Power Beyond Belief, #1 Rated Battery Powered Platform | EGO (egopowerplus.com)