How do I choose a solar module?

Apr. 29, 2024

How to find the Best Solar Panel for Your Roof - EcoFlow Blog

Choosing the right solar panels can help you enjoy a sustainable energy future and move towards a greener lifestyle.

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Not only is solar power good for the planet, but it can also be good for your pocketbook. Traditional on-grid electricity is increasingly expensive and unreliable. Over time the upfront costs of a PV solar array can be more than defrayed by reduced utility bills.

But not every solar panel system will suit your specific needs. Read this guide to find out how to:

Explore the different types of photovoltaic panels;
Estimate the associated costs;
Determine which solar panel is right for your roof.

How to Choose a Solar Panel

1. Understanding the Types of Solar Panels

There are three main types of photovoltaic panels: monocrystalline, polycrystalline, and thin film. Each panel has pros and cons regarding efficiency, cost, and form factor.

Monocrystalline panels consist of a single silicon crystal structure. They have a dark, sleek appearance and boast the highest efficiency of the three panel types. They’re more expensive than polycrystalline panels, but they’ll produce more power in less space.
Polycrystalline panels consist of multiple silicon crystal structures. They have a speckled blue appearance. They’re less efficient than monocrystalline panels but are usually cheaper as well.
Thin-film panels are lightweight and flexible, allowing them to adhere to curved and irregular surfaces. They’re the least efficient, but their unique construction makes them suitable for maximizing available surface area.

2. Evaluating Solar Panel Efficiency

The conversion efficiency measures how effectively a panel converts sunlight into electricity. Higher efficiency requires less surface area for energy production, making it particularly valuable when space is limited.

Factors that impact efficiency include temperature, shading, and orientation. Solar panels will perform better at lower temperatures and when angled towards the sun. Any partial shading across a panel — such as from overhanging tree branches — can drastically reduce the power output.

Proper ventilation, minimizing shading, and optimizing tilt angles can enhance conversion efficiency, ensuring optimal performance and return on investment.

3. Determining the Size of Your Home Solar System

To determine the size of your home solar system, you first need to calculate your daily energy usage. Divide your electricity bill’s total kWh energy usage by the number of days it covers to find your daily energy usage.

Alternatively, suppose you’re primarily using your solar power system for backup power or to reduce your electricity bills by powering selected appliances. In that case, you can use the step-by-step process below to determine how much electricity you need.

Identify the wattage requirements of your appliances. Survey the starting and running wattage requirements of the appliances and devices you plan to plug into the generator. You can usually find the wattage requirements labeled on the appliance, but we’ve also compiled the starting and running watts of typical household appliances in the table below.
Convert volts/amps to watts. If your appliance’s power requirements are in volts or amps, you can calculate an appliance’s running watts with this equation:

Volts (V) x Amps (A) = Watts (W)

Count the running watts of your appliances. Add up the running watts of the appliances you plan to use — does the total exceed the running watts listed on your generator? If so, you should consider buying a generator with more output capacity.
Factor in starting watt requirements. Identify the appliance with the highest starting wattage. Add that appliance’s starting wattage to the running wattage total.
Calculate the sum. That final number is the total starting watts you need from your generator. As discussed above, to avoid overloading your generator, do not exceed its starting watts rating.

Starting and Running Watts of Typical Household Appliances

ApplianceRated (Running) WattsStarting WattsDishwasher13001800Washing Machine12002300Refrigerator/Freezer7002200Light Bulb60-750Microwave600-10000TV5000Toaster9000Vacuum14402500Coffee Maker10000Blender300800Clothing Iron15000Dryer54007000Toaster Oven12000Curling Iron15000Space Heater20000Laptop50-300020” Box Fan200350

Next, look up your area’s average peak sun hours. A simple online search can provide you with this information.

Then, figure out the rated power of your PV panels. Most residential rooftop solar panels will have a power rating of 400 watts.

It is crucial to remember that the rated power of a solar panel indicates the maximum amount of electricity it can generate under ideal conditions. Depending on numerous environmental factors such as cloud cover and temperature.

Under real-world conditions, solar panels typically generate between 25% – 90% of their rated power wattage during daylight hours.

Finally, we can do a few simple calculations to determine how many solar panels it will take to power your house.

Divide your daily energy usage by the average peak sun hours to calculate the kW output you require from your system:

Daily energy use (kWh) / peak sun hours (h) = energy output required (kW)

Convert kW into watts by multiplying by 1000:

Energy output required (kW) x 1000 = Energy output required (W)

Then, divide that required wattage output by the estimated output of your panels. For most locations, it should be safe to assume that your panels will output at least 75% of their rated power on average should be safe. For a 400W panel, that means you should estimate 300W of electricity production per daylight hour.

Energy output required (W) / PV estimated output (W) = Number of panels needed

4. Calculating Solar Panel Costs for Your Roof

A complete residential array will come with upfront costs in the thousands. However, the return on investment (ROI) usually exceeds these initial costs.

You determined how many PV panels your home might require in the previous step. The panels are the highest cost in a solar system — if you need fifteen 400-watt panels, you may be looking at a price of around $15,000. Factors that impact the cost include construction quality, power rating, conversion efficiency, and type.

However, the savings you experience will pay you back over the system’s lifetime, usually around 25 to 30 years. Here is a simple ROI calculation:

Lifetime Utility Costs – Lifetime Cost of Solar = Solar System ROI

If your expected utility costs over your system’s lifetime exceed your system’s price, you’ll receive a return on your investment. Often a substantial one!

5. Comparing the Price of Different House Solar Panel Systems

There are a few different payment schemes for purchasing solar panel systems, each with its pros and cons:

Cash Purchase: Paying cash upfront will provide the most significant long-term savings. You’ll own the system from the get-go, and you can avoid interest payments. Purchasing a PV system outright will also give you access to rebates, tax credits, and other incentives that leasing can’t offer.
Financing: As with other large purchases, financing your system can be enticing. A loan lets you pay for your system over several months or years, lowering your upfront costs. However, the interest on the loan will reduce the savings you could experience with a cash purchase.
Leasing: Some companies allow you to lease a solar system. They own and maintain the system, but you enjoy immediate savings on your electric bill. Leasing a system will have few upfront costs, but you won’t be eligible for tax credits and other incentives. Your long-term savings will also be lower than with cash purchases or financing.

There are many factors to consider when comparing the costs of different systems. Consider these factors to determine the best value for your budget:

System Size
Equipment Quality
Incentives and Rebates
Warranty
Installation Costs (DIY vs. Professional)

6. Understanding the Quality of Different Roof Solar Panels

The quality of solar panels is usually measured by their efficiency. Manufacturers determine PV efficiency by testing the photovoltaics in Standard Testing Conditions, which specify a room temperature of 25° Celsius (77°F) and 1000W/m2 irradiance.

Monocrystalline panels have efficiency ratings above 20%, while polycrystalline panels are around 15%. Even with the cost savings of polycrystalline panels, the higher efficiency of monocrystalline panels makes them worth it over the long term.

7. The Importance of Solar Panel Temperature Coefficient

The PV temperature coefficient indicates how temperature change affects a panel’s efficiency. It is expressed as a percentage per degree Celsius and represents the decrease in power output for every degree above a reference temperature (usually 25°C). For example, a temperature coefficient of -0.3% / °C would mean that the panel’s output decreases by 0.3% for every degree above 25°C.

As photovoltaics heat up, their efficiency decreases due to increased electrical resistance within the cells. A lower temperature coefficient means the panel’s performance is less susceptible to temperature increases, making it a desirable characteristic when comparing different panels.

8. Durability of Home Solar Panels

Solar panels generally last around 25 to 30 years before diminishing in output capacity by about 20%. Any panel you purchase should be resistant to harsh weather — an IP68 waterproof rating indicates durability. Solar panels rarely require maintenance, as there are no moving parts.

It is a best practice to keep your panels free of dirt and debris. Inspect and clean them at least every six months with a soft, lint-free cloth and gentle soap. Never clean PV panels with harsh chemicals.

9. Solar Panel Installation on a Home Roof

Rigid solar panels are permanent installations mounted on rooftops. They’re the best solution for residential systems where it would be impractical to repeatedly set up and take down 10-12 portable PV panels.

If you wish to forego installation costs, you can also learn how to install solar panels on a home roof.

EcoFlow’s Portable Solar Panels are an alternative to rigid systems that don’t require installation. They’re best suited to smaller builds or situations like camping, hiking, etc. They provide the same power output as a rigid panel but fold up for easy transport and setup.

Conclusion

Once you know what to look for, choosing the right solar panel for your roof is straightforward. Most homeowners will appreciate the efficiency and cost-effectiveness of monocrystalline panels, and with EcoFlow, you have your choice of rigid, portable, and flexible designs.

Frequently Asked Questions

How Efficient Are Ecoflow Solar Panels?

Most EcoFlow solar panels have an efficiency rating of 23%, thanks to the monocrystalline photovoltaic technology. That means the panels will convert 23% of available sunlight into electricity. Our panels go through testing under Standard Testing Conditions to ensure consistent quality.

What Direction Should Solar Panels Face?

Solar panels should face the direction receiving the most sunlight, which is south in the Northern Hemisphere. Proper orientation maximizes sunlight exposure, enhancing solar panel efficiency and energy production throughout the year. A tilt angle between 25 and 35 degrees is usually best.

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How To Calculate Solar Panel Efficiency?

To calculate solar panel efficiency, divide the panel’s electrical output (in watts) by the solar energy input (in watts per square meter) and multiply by 100 to express the result as a percentage. A higher efficiency indicates a panel can generate more electricity from the same amount of sunlight.

What Is the Best Roof for Solar Panels?

A large, unshaded, south-facing roof is best for solar panels. To optimize sun exposure, the roof should have a pitch angle of around 30 degrees (depending on the location’s latitude). An ideal roof should have about 480 sq ft (45 M2) of available surface area for installation.

How to Maximize the Efficiency of Your Solar Panels

To maximize the efficiency of your solar panels, follow these tips:
• Buy solar panels with a higher efficiency rating.
• Choose monocrystalline panels over polycrystalline.
• Do not install your solar panels in shady areas.
• Perform routine cleaning, removing dirt, debris, snow, and other foreign objects.

How To: Choose a Solar Panel | GreenMatch

Ok, so you decided to install solar panels at home and produce your own (and clean!) electricity but are unsure how to choose the right solar panels for you? Then keep on reading!

However, if you already have a good idea of which solar panels you’d like for your home and just want to talk to a professional installer, then we can help connect you now.

At GreenMatch, we have an extensive network of qualified solar panel installers across the UK. We can put you in touch with up to 3 reliable installers in your area. You’ll also receive quotes from each installer, so you can easily compare their prices and choose the one who offers the best value.

Click the button below to get your free no-obligation quotes and have your solar panels installed in no time.

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Find out How You Choose Your New Solar Panel

We’ve created the list below to serve as a guide to making a good purchase. You should always keep in mind that a solar panel system is a long-term investment, hence there are many aspects other than the price that you should take into account.

1. Solar Panel Cost

This is probably the first factor people consider when comparing solar panels. The solar panel cost is determined by different variables: the size (in Watts), the physical size, the brand, the quality of the materials, the durability (or warranty period) and any certifications the solar panel might have.

A key guide on how to choose a solar panel is to consider the cost. However, it shouldn’t be the one and only factor to be considered, since the least expensive panel might not be the most efficient and probably not the best option if you consider the long term. How to choose solar panels can be risky but, they have a long lifespan (more than 30 years), so it is more important to ensure a good quality system than choosing the cheapest option.

2. Solar Panel Quality

This takes into account how the panel is manufactured and the quality of the materials used to build the solar panel. There are different types of manufacturers producing panels that differ in quality, price, and efficiency. There are vertically integrated solar panel manufacturers which control each stage of the production process. They put a strong eye on quality and invest a lot into research and development (R&D). There are other manufacturers that only assemble panels, but usually don’t manufacture their own cells and don’t invest in R&D. They use more human production than robotic, but produce the most affordable panels.

When choosing your solar panel supplier it is wise to check the companies’ reviews or history and see what experiences clients had with each of them. Since you will make a big investment, it is important to do a bit of research and see if clients are satisfied with the product and the customer service, and if the company did all that it has promised.

3. Energy Efficiency

Solar panel efficiency is how much of the light the panel receives is converted into electrical energy and hence, how much power your system will generate. The more efficient, the better (and more expensive). It is not always the best choice to get the biggest and most efficient solar panel, since you might end up spending more money than you should to cover your energy needs.

You should assess your requirements and find the panel that best suits your needs: this means not underestimate, but also not to overestimate your needs. Likewise, you don’t need a Ferrari to take your children to school (you can have it of course, but you can do the same spending a lot less).

4. Temperature Coefficient

This refers to the impact that heat has on a solar panel’s operational efficiency after installation. Since solar panel overheating accelerates their ageing, the lower the percentage per degree Celsius, the better.

5. Durability

This could be an indicator of the manufacturer’s confidence in its products. Usually, solar panels have a 25 year warranty (as long as the company operates). If the manufacturer does not offer a long warranty period, you could suspect that their product is not very good and hence they don’t want to take any responsibility. In this case, be careful not to be mislead by a tempting price since you might regret it in the long term.

Of course, it is important to properly maintain your solar panels to increase the lifespan of them. Fortunately, they are easy to take care of and don’t require much maintenance.

6. Size

This takes into account the physical size and the size in Watts. You should make sure to install a solar panel system that is big enough to power all your appliances, and also that you have the space required to install it. The physical size of the panel will vary depending on how powerful the system is (the more Watts, the bigger) and the type of solar cells used to build the panel.

An average household would typically require a 4kW solar system. Watts are related to the output of the panel (a 200 Watt panel will generate 200 Watt-hours each hour under ideal conditions while a 100 Watt panel will generate 100 Watt hours) and they are directly related to the price of the system.

The wattage of the solar panel is probably the most important thing you need to get right since underestimating the number will lead to a lack of energy, and overestimating the wattage will lead to spending more money than you actually need.

7. Types of Solar Cells Used

There are different types of solar panels with different efficiencies. Although their names might sound confusing, it is good to know at least the name not to be out-of-topic if your supplier happens to mention this.

Monocrystalline silicon offers high efficiency and good heat tolerance characteristics with a small footprint. Polycrystalline (or multi-crystalline) silicon cell based solar panels are now the most popular choice in residential installs. There are also Amorphous (or thin-film) silicon cells, which use the least amount of silicon and are not very efficient. For an equivalent wattage, a crystalline panel will be smaller than an amorphous panel.

Find the Right Solar Panel System for Your Home

Now you have the tools to choose the solar panel system that best suits your needs and be immersed in the world of solar energy. You should always compare different offers and see which supplier you find more convincing.

To help you with this task, our team at GreenMatch can provide you with up to 3 quotes for free. You will be contacted by different suppliers with their offers and you can then proceed to choose the one you prefer (there’s no obligation to choose any).

Get your best deal

Quickly compare 4 FREE quotes