o make the most worthwhile solar purchase, you need to grips with the basics first. There are numerous factors to consider before deciding on the product, and you may become completely overwhelmed with options. So if you wonder how to choose solar panels wisely, simply go through the checklist below.
The type of solar cells
The very first thing to focus on is the cell technology used in solar panels, as it will largely determine the performance of your system. The panels are composed of multiple photovoltaic (PV) cells that collect sunlight hitting their surface and transform that energy into electricity to power our homes.
First-generation solar cells and so far the most common ones are crystalline silicon cells. They have been the dominant technology since the beginning of the 1950s still account for about 95% of the market. Natural silicon can be found in the Earth's crust in the form of silicon dioxide (also called silica) and silicate. To obtain pure silicon, manufacturers melt silicon dioxide or silicates with carbon at around 1,700 °C. Then silicon crystals are manufactured, which can be done in two ways. Manufacturers can either deposit purified silicon on heated thin rods to form multiple crystals or melt and then freeze silicon to obtain a single crystal. The first method is used to produce cheaper but less efficient polycrystalline solar panels, while the second one is used for premium monocrystalline panels.
So why are monocrystalline options considered better? The answer is simple: they are more efficient, thus ensuring a shorter ROI period and saving a homeowner more money. Plus, they last a little longer and perform better in high temperatures. Polycrystalline models fall short in terms of performance, yet offer an affordable alternative for those on a tighter budget.
Crystalline silicon isn't the only possible option, however. You can also consider choosing thin-film solar panels - second-generation panels made by depositing a thin silicon layer onto the plastic, glass, or metal substrate. These modules currently account for only around 5% of the global market, but their deployment is expected to grow due to the unique benefits they offer. They are lightweight and flexible, which means they can be easily installed on uneven surfaces and used in intricate building designs. They are also cheaper than traditional solar panels. On the flip side, they are much less efficient and require a lot of space, which is why they aren’t widely used for residential applications.
The size of your solar system
You will also have to determine the solar system’s size, that is, how much energy you want it to produce. The size of most residential PV systems ranges between 4 kW and 16 kW, so you will have to calculate the capacity you need to meet your household’s energy demand. An oversized solar system won’t be a problem if it is tied to the local electricity grid and works under a net-metering policy, as you will be able to sell any extra power your panels generate to the utility. But if you are off-grid, the excess energy your panels produce will be wasted.
A smaller PV system, on the other hand, won’t cover 100% of your energy needs. While for off-grid consumers this will mean the inability to run some of their home appliances, on-grid solar owners will have to compensate for a lack of electricity with energy from fossil fuels.
Solar power rating
All solar panels are given a power rating, also known as wattage, indicating how much power they produce under standard test conditions, such as the irradiation of one kilowatt (kW) per square meter of full solar noon sunshine, a panel temperature of 25°C and a 45-degree angle of incidence.
Most residential panels are rated between 100W and 400W. The cost of solar panels is typically measured in dollars per watt, so the total wattage of a PV system is one of the key factors affecting its final price.
But keep in mind that the power rating of a solar panel is not the same thing as efficiency. Even a small PV module with low wattage can be extremely efficient and vice versa.
Solar conversion efficiency
Another specification you need to look out for when choosing solar panels is their efficiency. Solar panel efficiency shows how good it is in transforming sunlight into electricity. For example, a panel with a 20% efficiency rating converts about 20% of the sunlight it captures into usable energy. The efficiency of the first silicon solar cells fabricated in the middle of the 20th century was only about 6%, but the rapid development of solar technology increased this figure dramatically. Most residential solar panels today are 18-22% efficient, with some latest prototypes reaching 42%.
Monocrystalline solar panels generally deliver the highest efficiency of up to 22% which makes them the best option for homes with space limitations, as fewer panels are needed to generate the desired amount of electricity. The efficiency of polycrystalline panels is lower, usually ranging between 15% and 17% due to the lower purity of silicon.
Heat tolerance of PV panels
Some people would assume that the hotter the climate is, the more energy solar panels generate. In fact, this is not true - the temperature has absolutely no effect on the amount of sunlight the panels collect. And what's more, high temperatures can even degrade their performance.
Heat tolerance of solar panels is measured with temperature coefficient - the percentage of power output lost for every degree above 25°C, or 77 °F. Most PV panels sold today have a temperature coefficient of about -0.3% / °C to -0.5% / °C, which means they lose from 0.3% to half of one percent for each increase in degree over 25°C. Therefore, choosing solar panels with a lower temperature coefficient will help you lose less output in the heat.
Durability of solar panels
Most solar systems last about 25 years before they begin to lose a large percentage of their efficiency. This doesn’t mean you will have to replace them, but you can expect their output to be considerably reduced. Solar panels typically lose 0.5-3% of their output annually, so it is better to install panels with a lower degradation rate to maximize the output during their lifespan.
Price of solar modules
As with any other kind of product, the price of your solar system generally reflects the quality you will get. According to the report by Wood Mackenzie and the Solar Energy Industries Association (SEIA), the US average cost of a residential solar system is $3.25 per watt. The cost of high-performance monocrystalline panels ranges from $3 to $5 per watt, which means a standard 5 kW system can cost anywhere between $15,000 and $25,000. Polycrystalline panels are considerably cheaper – the cost of the most basic models with low-range performance starts at $0.90 per watt. And while some buyers will be drawn by lower prices, the cheaper system means they will need more time to break even with the investment and will save less money in the long run.
Consult with your installer on how to choose the best option for your home
Before choosing intensity of solar panels, it is important to delve deeper into the topic first. And while exploring the basics on your own is necessary, you will definitely need an expert opinion as well. Consultation with a solar installer is an essential part of the process: the specialist will provide a selection of options available and advise you on how to choose the best PV panels for your individual case.
To sum up, choosing solar panels is not as hard as it may seem
Choosing the right solar panels is no easy feat, but luckily it isn't a path that goes entirely unbeaten. Collect as much information as you can and compare models by the parameters listed above. And don’t hesitate to ask your installation company any questions – it will help you not to make a mistake with the choice.