Intelligent energy solutions by Autarco and Tigo

Intelligent energy solutions by Autarco and Tigo

For rooftops with a lot of shade, or in cases where insurers require that the voltage of the solar power system can be reduced to a safe voltage, Autarco, in combination with Tigo optimizers, offers a highly intelligent energy solution where safety and cost efficiency are paramount.

In addition to major cost benefits and lower installation costs, our intelligent technology reduces the risk of errors and connector mismatch. Autarco is the only Dutch brand that offers a total solar solution in which all parts are developed in-house. This way we can guarantee that all connectors of an Autarco system are equipped with original MC4 connectors from Staubli. This relatively small adjustment significantly reduces fire risk and makes Autarco systems one of the safest on the market.

The benefits of these optimizers

Great cost benefits in the calculation

The biggest advantage of Tigo, in combination with Autarco, is that only the panels that suffer from shadow fall need to be fitted with Tigo optimizers. But then you must be able to determine which panels these are! This is very easy with the Helios software from Autarco.

The result: savings of up to 10,000 euros on a 150 kWp system compared to a SolarEdge system, for example, where the entire roof is always provided with optimizers, even though most panels do not suffer from shade.

For instance:

  • A roof with 500 panels, of which only 20 panels are shaded.
  • 250 SolarEdge duo optimizers, cost € 12500 (estimate)
  • 20 pieces of Tigo optimizers, costs € 540

The saving is therefore almost € 12,000 in material costs. This does not even include the additional installation costs of installing 230 optimizers.

Selective application with different Tigos

Autarco works with both the Tigo optimizer (TS4-A-O) and the safety module (TS4-A-S). These two products differ in function but also in price and can be used in combination in a solar power system. If an insurer requires that the entire roof can be switched back to low voltage immediately, then you only apply optimizers to the panels that are actually in the shade. On the other panels you apply the cheaper safety modules, which only ensure that the panel goes back to 1V when necessary. The combination means that you can optimize the business case for your customer because you are more specific and cheaper but just as safe!

Lower installation costs

In cases where there is only limited shade on the roof, an installer can save considerably on installation costs, as far fewer Tigo optimizers are installed.

Less chance of errors

It is often underestimated: optimizers increase the risk of errors because there is more electronics on the roof. Using the Helios design software developed by Autarco, users are able to reduce shadow drop to less than 5% loss in most cases. In such a case, it is not economically profitable to include optimizers in the system because the additional returns from optimizers do not contribute positively to the business case of your customer. A normal system with string inverter in combination with the kWh guarantee guaranteed by Lloyd’s of London is the best solution.

Why? Optimizers are precious. In addition, with optimizers you increase the number of connections on the roof and electronics are placed on the roof, which can also break. Because Autarco, in combination with Tigo optimizers, minimizes the number of optimizers required, and precisely adjusts it to the actual economic need, such a system is less susceptible to malfunctions than, for example, a SolarEdge system with many more optimizers on the same roof surface.

Module level rapid shutdown and arc fault detection

Tigo optimizers (in combination with Autarco), like competing systems, have the option to switch high voltage on the roof back to a safe voltage if necessary (or required by insurance). All Autarco inverters are also equipped with arc fault detection.

But with Autarco, arcs are not only detected. They are also prevented. In a SolarEdge system,different makes of MC4 plugs are clicked together. An Autarco system is much safer, because Autarco only uses original Staubli MC4 plugs on panels, inverters and Tigo optimizers.

Autarco, in combination with Tigo, offers a full-fledged solution that ensures that the risk of fire due to electric arcs and connector mismatch is minimized, while any extinguishing work can be carried out safely because there is no high voltage present.

About Autarco

We are a Dutch company specialized in solar power solutions for pitched and flat roofs. As a solar producer we focus on what we are good at: innovation and delivering optimal total solutions. We have a strong network of Authorized Dealers who are specialized in the installation and maintenance of Autarco solar power systems.

The advantages of an Autarco system at a glance:

– One complete solar power system (solar panels, inverters, mounting system, monitoring software, cables, connectors, etc.) from one Dutch brand.

– Unique kilowatt-hour (kWh) guarantee insured by Lloyd’s of London

– 24/7 system monitoring

– Seamless integration into the Helios design system

– Asset Management

– Monitoring per panel possible via the Tigo portal


Solar up under lockdown

Did Netherlands Covid-19 lockdowns affect the performance of solar systems

On March 15, the Dutch PM announced that “All schools, cafes, restaurants and sports clubs will be closed in the Netherlands to stop the spread of coronavirus.” 3 months of hard lock down that most of us would happily forget followed. As we find ourselves starting to emerge from a second lockdown and starting to see light at the end of the tunnel it’s a good time to go back and see if we can find some positives from a difficult time.

It is reasonably well established that the natural environment benefited from a reduction in human activity during lockdown periods across the globe. Two of the most known examples are the clearing of the canals in Venice (some say the return of birdlife was also a result, but any one who has been to St Mark’s square knows there are plenty of birds in Venice!) and the reduction in pollution over Wuhan.

But what about the more direct impact on solar systems in the Netherlands? The graph below shows a clear increase over the 5yr and 30yr averages for the lockdown periods.

Impact of Dutch lockdown on irradiance

Graph 1

Irradiance overview Netherlands

Graph 2

The irradiance levels in April and May increased on the 30yr average by 29% and 24% respectively. These values are at the extremes at what would be expected based on normal variation in weather conditions, but are theoretically possible. It is worth noting that the combined irradiance of April and May achieved in 2020 has not been exceeded since records began in 1983! Statistically these sunlight levels could be considered a 1 in 50 year event.

As the lockdown began to ease at the beginning of June the irradiance levels returned to their long term averages, which in our opinion provides further evidence that the lockdowns did in fact contributed to higher irradiance levels throughout the Netherlands.However, while the data certainly suggests a direct impact, the natural variability makes it difficult to conclusively state that this is caused by the lockdowns.

Irradiance variation is widely misunderstood and the effects on performance under-estimated.

Graph 2 shows that during the boom years of Netherlands solar, irradiance levels have consistently been above the long term averages.

When an expected yield is provided for a system in design phase a long term average of irradiance is used (more on P50 andP90 later). Over the past 5 years actual irradiance has been 10% above historic levels in the Netherlands, the logical expectation is that system performance should be over achieving the expected yields provided pre-build by 10%.

It is difficult to predict future trends in irradiance, clearer skies obviously have a positive impact, but there are also much larger climate and weather affects that influence these trends. A return to historic averages, or even lower, are very likely within the SDE timeline of projects being built. When this happens, we expect a lot of rooftop asset owners will discover their systems, they thought were doing well by meeting expectation are actually underperforming, and have been ever since installation. 

For larger ground mount systems and the largest industrial rooftops with owners who are solar professionals, pyronometers are used to measure on site irradiance and monitor relative performance, but these level of sophistication remains quite rare for the majority of SDE projects.

The Autarco way

At Autarco, all of our performance metrics are based on actual irradiance data that we receive in 15min intervals for all of Europe. Using the digital twin in Helios, this irradiance data is used to generate true expected values (or retrodicted for the nerds). This Delivers a true base line for performance (referred to as Energy Performance Index (EPI) and ensuring all our systems are generating at optimal levels. It’s just one more example of how we use the power of data and digitilisation to deliver on our promise; “Solar made simple. Performance made certain”

SolarEdge vs. Autarco Total Solution

We are often compared to SolarEdge with respect to safety, so to make things easier for our dealers and potential customers we have put together a comparison table.

Connector mismatch

As a total solution brand, we can guarantee that all of the connectors provided with a commercial Autarco system use original MC4 connectors from Staubli. On the solar panels, on the inverters, on the inter-row connections and any loose connectors provided. This relatively straightforward benefit is impossible for a component brand to match with ease.

Even SolarEdge, who promote and push the safety message so strongly are not able to adequately control the leading cause of fire in solar systems, because ultimately, they do not know what connectors their optimizers will be matched with on the back of the solar panel.

Performance of optimizers

There are numerous very strong use cases for optimizers, particularly in heavy shade, but their usefulness is often overstated. We recommend interested parties to review this Research Report which also backs up many of our findings in the field. This study shows that PV systems have typically a higher yield if no module optimizers are applied.

Interested? Get a free roof scan and follow up from one of our Authorized Dealers near you.

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Are Autarco modules bankable?

Yes, Autarco modules are bankable. ABN Amro, Triodos, ASN and most major banks in The Netherlands are willing to finance projects using Autarco’s products. If this isn’t the meaning of bankable, then what is?

We could end there and have the shortest blog post ever. However, we are aware that our proposition is different to other component brands and are happy to explain more. Autarco handles product risks and product quality better than any component brand and we can back that claim up with reports from independent and well recognized companies in the industry as well as historical system performance data.

We are very proud of our approach to manufacturing high quality and reliable products and have nothing to hide.

What is our manufacturing approach?

Autarco does not own any factories ourselves. We have our own designs and specifications that are tighter than the industry standard and then contract the best factories in the market to manufacture these products on our behalf. This is a modern approach to manufacturing that is the standard in many industries more mature than the relatively young solar PV industry. Good examples are the electronics and automobile industries where brands work with a variety of specialized component manufacturers and themselves focus on design, assembly and service.

This approach not only allows us to deliver exceptional levels of quality and reliability, but also gives greater flexibility in rapidly changing markets, such as the solar market we are in.

Where do we produce our products?

Our MHE Series modules are produced by Chint, a global electronics giant with annual revenues greater than US$10bn. Founded in 1984, Chint has developed a business network in over 140 countries and regions with more than 30,000 employees. Chint’s solar brand Astronergy is one of the most recognized brands in the market and is regularly featured in:

  • DNV GL Top Performer in all tests (Thermal Cycling / Damp Heat / PID).
  • Bloomberg Tier 1 lists.

How does solar panel production actually work?

Typically products are defined and produced as follows:

  • A single certified product code relates to a set of endorsed components (cells, backsheet, glass, etc.) called a Constructional Data Form (CDF) or simply a Bill of Materials (BOM).
  • For each component in the solar panel there is a range of certified suppliers of higher and lower quality, meaning it is possible to have different levels of quality within the same product code. Without proper control, buyers should assume they will get the most convenient (cheapest) option.
  • The certificate will also list a number of allowed factories. Many of the other “OEM” factories are smaller locations with poorer quality equipment, lower automation and looser quality control than the main factory. Even within the main factory, different production lines will often have different levels of automation and equipment age.
  • The module will have a production process with criteria for each step with regards to tolerances that are acceptable. This defines among other things the number and length of micro-cracks that are allowed before a module is deemed to be defective.

So when you buy a solar panel from a factory or third party without knowing the exact BOM, production location and quality specifications you may be receiving an inferior product to one that the same brand would use in their own projects. Component brands know they can get away with delivering cheaper versions to the rooftop/distribution market and as long as there are no massive failures, lower performance will have no consequence for them.

How does Autarco manage quality

Autarco has a stake in the performance of all of our systems so we do everything possible to control quality:

  • We restrict the components used to a specified BOM of only the best components.
  • We only allow production on the most advanced production lines.
  • We enforce higher quality specifications than industry standard.

In this manner, an Autarco module is not just identical to any other module produced by Astronergy, it is in actual fact likely to be of superior quality. To give two concrete examples with the MHE series (without going into nerdy quality assurance details):

  • We only use the superior original Staubli MC4 on our modules, while Astronergy normally uses an MC4-like connector.
  • We have tighter dimension tolerances than Astronergy normally applies, to remove inconvenient gaps in the middle of the modules and issues during installation.
  • We apply stricter cell sorting to ensure a more aesthetic module.

We have third party audit and quality reports available on request if required.

What about warranties and guarantees?

At Autarco we believe intensely in the benefits of our total solution approach with insured performance guarantees. A performance guarantee that financially compensates when the system is underperforming is far more meaningful to rooftop solar owners than the solar panel component warranties, but any system performance guarantee we offer is always in addition to all the industry standard solar panel warranties, including:

  • 10 year product warranty
  • 25 or 30 year power output guarantee

Our agreements with Chint have the following statements;

“Chint declares hereby that all PV modules produced for Autarco Group BV or any of its subsidiaries are covered by the Chint “Limited Product Warranty” and 25 year “Limited Peak Power Warranty” terms on which you find enclosed.

The above means that, in case Autarco Group BV is no longer actively trading, any warranty claim against a faulty PV module manufactured by Chint for Autarco Group BV or any of its subsidiaries will be honoured by Chint as per the “Limited Product Warranty” and 25 year “Limited Peak Power Warranty” terms provided that it is a proven product defect.”

The solar panel Warranties are also fully insured by Munich Re or Lloyd’s of London.

The Dealer and end customer in effect receive four different levels of security on the warranties:

  1. Autarco: Primary and EU based cover
  2. Chint: Underwrite Autarco product warranty
  3. Product Warranty Insurer: Underwrite Chint product warranty
  4. kWh Guarantee Insurer: Underwrite Autarco kWh Guarantee


Our manufacturing approach means Autarco will never be listed in the Bloomberg Module Tier 1 list ourselves as one of the requirements is to own the factory. However, the Autarco MHE Series module is at least as good as the Astronergy modules on the list. Bankability is a measure of a banks willingness to finance a project and we have never experienced a bank unwilling to finance an Autarco project, conversely, our partners have typically been able to lend at lower rates thanks to the security provided by our insured performance guarantees.

In short, yes, Autarco modules are bankable.

A performance boosting summer

With last year’s long and hot summer not yet forgotten, it will not come as a surprise that 2018 was a good year for the owners of PV systems. But how does this year relates to previous ones? What does it mean for the long term performance of PV systems? Autarco’s engineers collected the data and found out.

What was the influence of the long summer?

In a previous blog on this site, we already saw that February 2018 was a very sunny month, related to other Ferbruary months. But the graph below also shows that this is of little impact on the year’s total yield, since it is only a small part of it. Of course, it’s the summer months that count. Typically, in the Netherlands you will generate 40 to 45% of a total year’s yield in May, June and July, when the days are longest and the sun is high in the sky. In 2018, these months were particularly sunny and warm, pushing the total irradiance for 2018 to values 8 to 15% above the long term average.

Average irradiance per day (W/m²)

15% more irradiance, what’s the deal?

The next graph shows the yearly irradiance for five locations in different parts of the Netherlands. First thing to notice is the year to year deviation. It also shows that 2018’s high irradiance levels are quite rare, we need to go back fifteen years to find similar values. As an installer or (potential) owner of a PV system, it might be tempting to consider yourself well off, based on last year’s yields. But it’s because of these deviations in the graph, that last year’s peak irradiance gives us no information whatsoever for the coming years. Therefore it is of great importance to keep looking at long term averages, in order to obtain realistic expectations on yields.

Total yearly irradiance (kWh/m²)

So what does this mean for my PV system?

In terms of the yield of any PV system, the irradiance alone does not tell the complete story. Sure, it’s important, but yield is also affected by the pitch and azimuth of the modules, the system’s efficiency and shade losses.

Autarco’s design and monitoring software has all the answers. By modelling a PV system, an exact virtual copy is created, where all the yield influencing aspects as described before are taken into account. Based on the design a yield prognosis is calculated, using the long term average irradiance for the exact location of the system. This makes it possible to very accurately calculate the return on investment for any PV system, and is much more secure than the standard figures still used to estimate yields in terms of kWh per kWp. After all, these numbers do not tell the whole story and are often too high.

After installation and registration of an Autarco PV system, the installation is verified to be sure that it is exactly similar to its virtual twin. By doing so, Autarco is able to monitor performance on all of its systems with great accuracy. We don’t look at standard figures and estimates whatsoever, based on the virtual twin and the actual meteorological satellite data, we know exactly what a system’s yield should be at any time. By comparing this with the actual yield as communicated by the inverters, we know immediately when something’s wrong and maintenance or repairs should take place.

Find out more on our design software here.

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The argument for now

The installed price of solar PV systems has decreased by an incredible 70% over the past 5 years, leading many potential solar owners to question whether they should invest now or wait for further price decreases. The answer for potential beneficiaries of the Dutch SDE+ program is clear; there is no better time than now.

Install costs in solar are decreasing...

The increased price competitiveness has driven the solar industry to record installations in 2017 of a massive 80GW compared to 20GW in 2012.  As a result, solar is now at grid parity in many parts of the world and we even see solar projects breaking ground in regions where there are additional taxes applied on solar as opposed to supporting subsidies. This is undoubtedly brilliant news, but it also gives rise to a common question asked by end customers; “If the price decreases so rapidly, why should I invest now? Isn’t it better for me to wait until solar is even cheaper and then invest?” There is sometimes strong merit in this argument and it can only be answered on a case by case situation per market.

“Value of SDE+ Payments decreases over 40% in 3 years”

... but so is the SDE+ subsidy.

For the Dutch market however, particularly the commercial SDE+ market, the answer is a resounding “DO NOT DELAY”. Potential owners should be absolutely utilising any SDE+ subsidy allocated or making the effort to apply during the current Autumn 2018 round due to close in October. Even considering the urgent need for everyone, individuals and businesses alike, to take action in reducing CO2 emissions to limit global warming, there is a purely economic decision to act now: acting now maximizes the lifetime returns of your solar system.

There are 4 primary factors that determine the financial performance of any solar system over a 15 year investment window. You can of course perform the same analysis over 20 or 30 years if desirable, but for the purpose of this article we take the 15 year subsidy period.

SDE+term SDE+rate Self-consumption correction Change from year 1 Deadline
2015 € 0.096 no Signed contract within 1 year, commissioning within 3 years
Spring 2016 € 0.084 no -12.5% Commissioning within 3 years
Autumn 2016 € 0.084 no -12.5% Commissioning within 3 years
Spring 2017 € 0.092 no -4.2 Signed contract within 1 year, commissioning within 3 years
Autumn 2017 € 0.084 no -12.5% Commissioning within 1.5 years
Spring 2018 € 0.062 yes Commissioning within 1.5 years
Autumn 2018 € 0.056 yes -42.2% Commissioning within 1.5 years

*The SDE+ rates in this table assume the highest price brackets and standard correction rates as published by RVO. In the case of the 2018 subsidy, a self use percentage of 50% is taken into account. This number will differ between projects, but even with a theoretical self use of 0%, the maximum subsidy is lower than years before. We are looking at systems <1 MWp.

Why investments in solar should not be postponed.

These data demonstrate a compelling case to invest now! If you have a SDE+ subsidy already approved, the lost opportunity for letting this lapse in the hope of reapplying later when solar costs are lower is clearly a fallacy that is not going to turn out like you hope. Furthermore, with more parties stepping into solar, competition for SDE+ budget is getting harder, leading to smaller chances of getting your request for subsidy awarded.

Recent changes in the Chinese market have resulted in price reductions and further changes to the global supply-demand situation are possible in the coming months. We will soon cover these impacts on the European market, both negative and positive, following the final MIP decision and further clarity on tariffs in key markets like India, Turkey and the US. Even these product price decreases don’t compare with the opportunity cost of failing to act now.

Potential system owners who look at falling module prices and think waiting is the best option, can be convinced to act now by emphasizing three key points;

  • Benefit and availability of SDE+ subsidy is decreasing at a faster rate.
  • Improving global economics is already pushing interest rates higher. Increasing one of the major costs of any solar projects.
  • We need climate action now.

If you have SDE+ customers who aren’t convinced or looking for something extra to convince them we are ready to help. Get in touch to offer a fully secured business case.

Do modules like this summer heat?

July was hot this year. Very hot. But this nice summer weather is good news for your solar modules, right? Or is it? In this article we look at the influence of these conditions on PV systems.

Due to the bright sun, at almost the highest point in its orbit and with hardly any clouds in the sky, irradiance reached record heights over the last couple of weeks. As shown in the graph below, in the Netherlands irradiance was 25-30% higher than the long term average.

So there was a lot of energy coming our way, ready to be harvested by solar modules. But this great irradiance comes with high temperatures, that surely didn’t go unnoticed. Tarmac was melting, bridges expanded until they wouldn’t open anymore, and crops drying out on the fields. The question now is, how do your PV systems react to this heat? Do they thrive under these conditions? Or are they taking it easy, as we humans tend to do?


It might sound counterintuitive, but where solar panels love the sun, the don’t particularly like the temperature coming with it. Solar modules are meant to convert light into electricity, not heat. To see exactly what this heat means for the yield of a PV system, we conducted a case study for an installation in our hometown Eindhoven. In this example, we are looking at a set of modules facing South, in an optimal 35° pitch. Looking into the meteorological data we collect on a daily basis, the average temperature in Eindhoven appeared to be around 3°C higher than the long term average. But because this higher ambient temperature is combined with the high irradiance and the heat generated by the modules themselves, it causes the average cell temperature to be 6°C higher than normal, easily reaching values as high as 60°C! This is bad news, because solar modules become less efficient in high temperatures, as do all semiconductors. Higher temperature means a lower potential difference within the cells, which results in lower voltages. And although the current might be a bit higher in situations like these, it doesn’t compensate the lower voltages, resulting in lower yields. After all, the output in watts is the product of voltage and current.


For our test case, irradiance for July was 34% higher than the long term average. At first glance you might expect yields to raise accordingly. Due to temperature losses, they don’t. The yield this month was only 30% higher, the difference being caused entirely by the high temperatures. As expected, this difference is higher than in previous years with their slightly milder summers. Usually, we look at a difference of around 1,5%, rather than the 4% for this year.

So yes, this sunny summer weather leads to higher yields for your solar modules. However, not exactly as high as you might expect. But while overall efficiency might be a bit lower, due to the high irradiance and the number of daylight hours, July will still be the best month of the year, as it is every year.

Temperature is only one of the many factors that influence the yield of a PV system. All of these values are taken into account in our design software, so it can accurately calculate the expected yields for any PV system. These exact calculations form a major part in Autarco’s insured kWh guarantee.

Acknowledging the importance of O&M

Last month Solar Power Europe launches the ‘Solar O&M Best Practices Mark’. With this self-certification-based label, Solar Power Europe acknowledges the importance of O&M within the solar business case, and the value of it for all stakeholders.

As part of the task force developing this new standard, Autarco is now using its experience to move the industry forward. With our unique kWh guarantee, like no other we know the importance of proper maintenance in order to ayour return of investment. A well designed and installed PV system with high quality products is not the complete story, only with a proper O&M contract in place you will be certain to get the best possible ROI over the complete lifespan. As our industry matures, the install-and-forget mentality we still see too often should not longer be accepted. Not by investors and system owners, nor by installers. This is one of the reasons why Autarco updated its kWh guarantee policy. By doing so, we acknowledge the importance of good O&M and high quality asset management, and respect both the owner’s and the installer’s time and effort. From now on, we are able to offer higher guaranteed and insured yields for utility scale installations, when a proper O&M contract is in place.

kWh Face Off! East-West Vs South

Every time a commercial flat roof PV system is designed a decision to build facing South or East-West must be made. While everyone knows European solar systems will perform best facing South with a decent sized pitch, there are a number of other factors at play that influence the most profitable solution for a commercial PV system owner.

Many analyses of East-West vs South facing PV systems for commercial projects still focus on year 1 costs (price per Wp) and estimated production. In the same way that we offer a kWh Guarantee that offers reduced risk and simplicity to installers and system owners, we believe the East-West vs South question is best considered looking at the returns on investment and the levelized cost of energy. After all, solar PV customers are not looking to solve a one-off component hardware problem priced in EUR/W, they are looking for a long term energy solution.

This long term energy solution needs to consider the total costs related to the yield of a system for its complete lifespan and of course the risk related to the solar production over the same lifespan. So what are the expected returns of a solar system?


Let’s look at an example where we compare both alternatives for a reasonably sized commercial project in the Netherlands. We cover some of the assumptions we have made in detail below.

Over the 15 year life of the Dutch SDE+ subsidy, the system owner can generate nearly 20% more profit with an East-West system at a slightly higher return on investment. While a south facing system in the Netherlands does produce nearly 7% more yield per Wp, this power is more costly given the current solar economics of 2018.

Azimuth Annual yield per kWp (kWh/kWp) Annual yield per m² (kWh/m²) Annual savings (€) Cost of energy produced over 15yrs (€/kWh) ProjectIRR *
East-West 934 127 20,443 0.059 19.30%
South 997 100 16,000 0.076 17.20%

*IRR excludes any fiscal/tax benefits

Autarco’s insured kWh Guarantee lowers the risk profile of the project for the bank, helping system owners and investors unlock more debt at lower costs. As a result, the additional initial investment required for an East-West system should not be a barrier to completion.

The drivers behind this result and some of the key factors to consider are discussed below. Regardless of the choice, Autarco’s kWh Guarantee, insured by Lloyd’s of London, delivers peace of mind to both installers and end customers by providing a minimum production level that protects your investment.

Yield per wattpeak.

Assumption: Face Off result
Base Assumption: 10/12 degrees Win for South. 7.3% more yield/Wp.
Factor: Greater module pitches A 30 degree pitch south system will produce 13% more than a 10 degree pitch East-West system.

As we all know, the yield per modules it at its best when the module is facing South. However, since the pitch of the solar panels in flat roof mounting systems is relatively low (10°-12°), the non optimal azimuth of East-West systems are more than compensated by other benefits.

Yield per m².

Assumption: Face Off result
Base Assumption: 10/12 degrees Win for East-West. 22.5% more yield/m².
Factor: Spacing of South facing Can reduce difference to around 8% if weight is not an issue.

The yield per module might be a little less in East-West facing systems, the total number of installed modules outweighs this, leading to much better total yields per m² roof surface. This difference can be as much as 25%, so symmetrical systems are the way to go when roof surface is limited.

Impact of increasing pitch and reducing row spacing of South facing systems is offset by other issues such as shading and ballast requirements.

Yield distribution.

Assumption: Face Off result
Base Assumption: Low module pitch (10-15) Marginal win for East-West
Factor: Greater module pitches Makes East-West more competitive by increasing self consumption.

Another supposed advantage of symmetrical systems that is widely published is the distribution of yield over the day. Where a South facing system has a clear peak around noon, with solar panels facing East and West the yield is more evenly spread out. This results in a more steady production of kWh and a better match to the actual energy usage. However, the most common flat roof structures use a pitch between 10-15 degrees, so this advantage is really quite negligible as shown below.

Because of the difference in azimuth, yield distribution differs over the course of a day.


Assumption: Face Off result
Base Assumption: No Shade Win for East-West
Factor: Morning or evening shade Makes South more competitive. Morning or evening shade will result in greater shade losses for East-West facing modules

When the modules are directly facing the sun they experience higher plane-of-array insolation – the amount of direct and indirect sunlight hitting the surface of the solar panel – which of course leads to higher yields. Since most shading occurs during sunrise and sunset, the general influence of shade is worse for symmetrical systems. Common rooftop obstacles such as air conditioning units and sky lights are easily capable of causing 5-10% shade losses for East-West systems if the PV array does not avoid appropriately and plan stringing accordingly.

The Autarco modelling software is designed to make exact shading calculations, making it possible to compare both alternatives on any given location.

With modules facing south, there is a small amount of self-shading from one row to the next.

Mounting costs and ballast.

Assumption: Face Off result
Base Assumption: 10m roof height. Clear win for East-West
Factor: Roof height or increase module pitch. The higher roofs and greater pitches strengthen the East-West advantage.

With a symmetrical (East-West) system, you make the most efficient use of the mounting system. Since there is hardly any space between the modules, there is no redundant mounting to be installed. Due to its nature of back to back modules, a symmetrical system is less influenced by wind loads. They form a closed system within itself, without the need to provide wind deflectors like South facing modules would need. You can save up to 15% on the costs for mounting when using a East-West facing system.

Apart from using less material per installed module, it saves on the need for ballast as well. This saves costs and labor, but more important, it lowers the total weight of a system, especially for roofs above 10 metres height. This can play an important role in the decision, mostly for industrial buildings where load bearing capacity of existing structures can be limited.

AC connection and other fixed costs.

Projects that have high fixed costs regardless of total system size also favour East-West systems. These could include things like;

  • Grid connections
  • Crane fees / scaffolding


We hope you found this analysis interesting and useful. We are committed to making solar simpler and less risky for installers and owners of commercial PV systems.  If you have any questions about how to choose the best solution for your project, please contact us.

Sunny February

At Autarco, we continuously monitor solar irradiation levels for locations where our PV systems are installed. By doing so, we are able to analyze whether the yields of these systems are as expected and all components work as they should. The collected data leads to interesting results when comparing one year with another or looking for differences between various locations around the globe.

It’s not uncommon that a months irradiation levels may change from year to year by up to 20%. This is one more reason an intelligent monitoring system that tracks your systems actual performance against actual weather conditions is so important.

See how Autarco can offer you this here.

Last winter was quite dark...

For example in the Netherlands, irradiance levels last December and January have been lower than the long term average. On top of that, snowfall led to small decreases in yield, mostly for flat-roof systems. However, since average yields in these winter months account for only a small part of the yearly total, the impact of an incidental snow cover is minimal. The Royal Dutch Meteorological Institute (KNMI) measured that the number of sun hours in December and January were both far below average, this had a big influence on irradiation levels in this period, as we saw in our satellite data as well. The winter months were truly dark this year!

... but February made up for it!

Fortunately, February 2018 showed an entirely different image. Sun hours are far above average values, even so that it is the second highest number since the KNMI start monitoring these data back in 1909. On our satellite data we see this resulting in irradiation levels that are indeed above average, up to 30%, depending on the location within the Netherlands. Together with the low temperatures and the days lengthening again, this boosts the overall performance of PV systems, resulting in good yields for this time of the year.