Buying Solar Panels For Your Home

It can be really exciting shopping for and buying a solar power system to generate electricity in your home. The choice of using the sun’s energy to generate electricity is a good one. Not only will you be helping Mother Nature by using a renewable source of energy, but you will also be saving money in the process. Choosing the best solar panels for sale is not that complicated when you know your facts.

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Finding Solar Panels For Sale

This guide will help you make an informed decision on which system is a good fit for your needs. When looking to buy, the goal is to have a reliable electrical output throughout its life, while at the same time having a minimal cost of installation. In this guide we will cover how to achieve this and what are the questions that need to be asked when deciding on the best panels for your home.

The prices and outputs are based on the material being used. So it can be confusing to make a decision without the sufficient background knowledge. Many find it hard to choose between the expensive solar modules on the market and the more conventional generic modules, which are cheaper and seem to be enough for their household electric needs.

Quick Check List

  1. The negative power rating (NPR) has to be as low as it can possibly me. It should not be more than 7%
  2. The higher efficiency cells will take up lesser space for amount of output and often has the same price as the less efficient panels.
  3. The PTC wattage rating is standardized and is a more accepted rating for residential systems.
  4. Panels from trusted manufacturers with a good track record will give you more security in your investment in the form of warranty and investment protection.

How Much Do Solar Panels Cost?

solar panels for saleFirst you have to look at the minimum warranted power. This is the maximum output that your photovoltaic (PV) cell is guaranteed to generate. It is one of the most important elements you have to take into consideration.

PV cells are always made in batches, and the manufacturers use the best samples to determine what the peak wattage is. So the rest of the manufacturer lot will not have such high rating. But the manufacturer knows that the majority of the panels will generate electricity inside a range of the peak wattage. Based on the quality of the silicon which is used, it ranges from 5% to 12% variance. So when you buy a PV cell of 200 watts (w) and there is a negative power rating of 10%, then you will only be guaranteed 180w by the panels.

The better brands of photovoltaic cells will have better silicon quality (higher efficiency) and will ensure that the NPR is no greater than 5%. So as a rule of thumb, it should not be more than 7%. If your rating is more than this, it will mean that you have to buy more modules to compensate for this energy loss. So when determining how much your solar panels costs, the efficiency rating should be used for a more accurate calculation.


Let’s look at an example. Say you have a 20KWh/day energy need, and you have 5 hours of direct sunlight in a day. So the system you install has to produce 4Kw/hour. And you are trying to choose between two different name plates, with both offering 200w panels for installation.

Panel A has a negative power rating of 5% and Panel B has a rating of 10%. The price for both panels is $700 per panel. When you calculate the actual guaranteed amount of power, you find out that Panel A is guaranteed to provide 190w whereas Panel B is guaranteed to provide only 180w. Based on your 4Kw/hour energy need required you find out you need 22 units of Panel A and 23 Units of Panel B. So by choosing Panel A you are actually saving $700. Since it has a lower NPR , it is also likely that it is made of a higher quality of silicon, which means that their efficiency is higher, and you’ll probably get more than the minimum guaranteed power. So always opt for the higher efficiency panels.

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Choosing The Best Cells: Efficiency

The higher the quality of the silicon that is used for producing the photovoltaic cells, the better the efficiency. The better the efficiency the more power you will get for every square inch the panel is producing. These high efficiency cells are made from large and expensive silicon that are monocrystalline.

The low cost photovoltaic panels are made from smaller and cheaper ingots and they are polycrystalline. They are often used to cut down on the cost of manufacturing. However the savings is not passed on to the end consumer and they are charged the same amount as the high efficiency panels. There is also a strong correlation with the high negative power loss percentage and lower efficiency. So the lower efficiency will drive up your long term investment.

PTC Rating

It is important to understand the difference between independent lab rating called the PTC (PVUSA Test Condition) rating and the STC (Standard Testing Conditions) rating The PTC rating is required by many states in the United States for PV panels. The test is mandatory before they can be sold in the market for consumer protection. The difference between the STC and PTC is that the STC is done by the manufacturer. The PTC however has a more superior bench mark and is made by an independent agency.

Following the same example of Panel A and Panel B, if the Panel A PTC rating is only 150w, whereas the Panel B has a PTC rating of 200w, then you will have to buy fewer Panel B than Panel A, making Panel B the better option. The PTC rating carries more weight than what the manufacturer tells you so always use that as your first choice.


The key component of a guarantee is the durability and reliability which spans throughout the lifetime of your PV cells. They tend to have a life of 20 to 25 years. Most manufactures will provide lifetime warranty of flaws which are manufactured. They also offer warranty for output defects for 20 years following purchase. That said, 20 years should be the bare minimum when looking for a warranty. This is important, because you will be encouraged to calculate your return on investment for this period.

Not all solar panels for sale have a good track record when it comes to reliability or a brand name that adds value to their warranty. Many companies come and go in the industry. Your warranty is valid only for the life of the panel company. Its highly likely that 5 years after buying them from a company, they go out of business and 5 years following that you have some defects in your panel. There will be no company to honor your warranty and you would have lost a lot of money by not realizing your returns.

So the best and probably the safest way to ensure this does not happen is to always purchase from a company that has a proven track record. It may be cheaper to purchase from some alternatives, but the risk is not worth taking. It will just kill your investment in solar technology by giving you meager energy savings. So buy from the right companies and save in the long term.


Buying a PV power system is not a difficult task if you know what you should be looking for. Though it is a very exciting investment, you need to be very careful so that you do not spend more than necessary and you do not invest in the wrong panels which do not give you, your return on investment.

The industry has its share of unscrupulous products and companies. When it comes to buying yours, remember the adage, “If it sounds too good to be true, it probably isn’t.” It’s better to shell out a few hundred dollars more and save money in the long term than to save a few hundred dollars now and lose money for the next two decades.

Find panels with a low NPR of not more than 7%. Go for with higher efficiency cells as the entire system they will take up less space per output, and they are sometimes the same price as the less efficient ones. Look at the PTC wattage rating as it is a standardized and more accepted rating than when compared to the STC. Always purchase from trusted manufacturers with a good track record as it will give you more security in your investment in the form of time proof warranty. Finding solar panels for sale is not that difficult, when you know exactly how to do it.

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