Frequently Asked Questions

At Sun Powered Yachts we understand you will likely have some great questions about marine flexible solar panels, the SunPower difference and how you can install a SunPower solar system on your yacht. 


We hope that you will have found a lot of great info so far and can also use the FAQ page as a good resource.  Scroll down, or click on the search icon and type what you're looking for, to find out more. 

(Note: see if we're available on chat to answer your question right away and also check back as we're always adding more FAQs to this page.)

Where can we find you?

Sun Powered Yachts is typically based on the Big Island of Hawaii but for the next 15 months we will be based aboard our sailboat 'Blake' a Dufour 382. We have sailed across the Atlantic with the ARC rally and will now be exploring the Caribbean and Central America.

We're happy to answer any questions on the phone & email about sailing and going solar aboard your yacht. We have plans to exhibit at a number of US boatshows in 2022 and looking forward to meeting you next at the Miami International Boatshow Feb 16-20.

Who is SunPower?

Since 1985, SunPower has been leading global solar innovation. SunPower solar panels consistently deliver more energy and long-term peace of mind with the highest performing solar power systems available. SunPower is the top solar energy choice for homeowners and businesses around the world.

  • Global headquarters based in Silicon Valley since 1985

  • Total solar energy generated >18,000,000 megawatt hour (MWh)

  • Diversified global portfolio leading residential, commercial and utility solar energy markets

  • World's highest efficiency solar panels featuring SunPower® Maxeon® cell technology

  • More than 750 patents for solar technology

How long has SunPower been manufacturing flexible solar panels?

SunPower has been designing and manufacturing high efficiency Maxeon™ solar cells for their own residential and commercial panels since 1985. They have been selling these Maxeon™ cells to original equipment manufacturers (OEM) for several years who, to varying degrees of success, have been making their own models of flexible solar panels. SunPower designed and released their first branded flexible solar panel in July 2017 called the E-Flex Series and includes the 50W, 100W, 110W & 170W panels.

What is the E-Flex Series from SunPower?

The E-Flex Series is currently four variations of flexible solar panel, the 50W, 100W, 110W and 170W models (new March 2019) As always SunPower continues to innovate and develop new products and will be looking to add to the E-Flex Series in the future.

What is the best way for me to stay up to date with all the changes?

Simply submit your email address at the bottom of our home page to receive our e-mail updates. Don't worry we won't be spamming you or selling your data, we just want to let you know about new products in the E-Flex Series, developments in the tariffs imposed on solar imports and other news from the solar & sailing industry.

Is the Junction box waterproof?

Waterproof is a vague term and has varying degrees. The International Electrotechnical Commission (IEC) has developed the Ingress Protection (IP) rating system which classifies protection provided against the intrusion of dust and water. The SOLARLOK Micro-Junction box is manufactured by TE Connectivity and has a rating of IP67 protection - as such it is protected from total dust ingress and against effects of immersion in water to a depth of 1 meter for up to 30 minutes.

What is the difference between monocrystalline and polycrystalline solar cells?

Both monocrystalline and polycrystalline solar panels serve the same function: they capture energy from the sun and turn it into electricity. They are also both made from silicon. To make solar cells for mono-crystalline solar panels, silicon is formed into bars and cut into wafers. These types of panels are called “mono-crystalline” to indicate that the silicon used is single-crystal silicon. Because the cell is composed of a single crystal or ingot, the electrons that generate a flow of electricity have more room to move. As a result, monocrystalline panels are a black hue which is more efficient, and can handle temperature and shade variations better than polycrystalline panels.

Polycrystalline solar panels are also referred to as “multi-crystalline,” or many-crystal silicon because there are many crystals in each cell. There is less freedom for the electrons to move, resulting in lower efficiency ratings than mono-crystalline panels. They may be less expensive, but lower costs results in reduced efficiency and a significantly less durable product than mono crystalline cells.

What does 23% cell efficiency mean?

Solar cell efficiency refers to the portion of energy in the form of sunlight that can be converted via photovoltaics into electricity. Current solar technology at the commercial level only converts electricity with a maximum efficiency of about 25%. This represents the 'ceiling' of panel cell efficiency (Note: higher results have been made in the lab).

SunPower® Maxeon™ Gen II cells (in the 50W & 100W panels) are 23% efficiency

SunPower® Maxeon™ Gen III cells (in the 110W & 170W panels) are 25% efficiency

SunPower makes the most efficient solar cells manufactured today which means more power in less space aboard your yacht!

What is a by-pass diode?

SunPower E-flex solar panels include a by-pass diode inside the junction box to protect your panel. When activated the by-pass diode will limit the total amount of power that can be dissipated by reverse biased cells.

Reverse biase can occur when voltage passing from a non-shaded cell (higher voltage) flows to a shaded cell (lower voltage) and generates heat. A reverse bias cell is essentially consuming power from it's neighbouring cells rather than generating it. The most common cause of reverse bias is partial shading.

SunPower cells are specifically designed with built in by-pass diode protection to maximize efficiency and mitigate the effects of shade on your panels. The cells have a stable reverse-biased breakdown that happens uniformly across the back of the cell. This results in much lower temperatures, prevents the 'hot spot' phenomenon occuring and as such the by-pass diode in the junction box is activated less often. A by-pass diode that is activated less often will last much longer.

Can I easily connect my E-Flex panels together?

The PV4-S connectors which are part of the junction box assembly are labeled positive and negative and can easily be connected to other panels. The design prevents the cables from being accidentally disconnected. A special MC4 tool is required for disconnection. These PV4-S connectors are the latest design from TE Connectivity and are MC4 compatible (which became industry standard since 2000 in compliance with NEC 2008). Panels can be connected together in either series or parallel to increase power production. They should then be wired to your MPPT Charge Controller before silently charging your battery bank.

What is Light Induced Degradation (LID)?

This is a loss of performance (1-3%) of brand new panels when first exposed to sunlight. Fortunately SunPower® flexible solar panels are NOT effected by LID and as such retain their high levels of performance (efficiency). The simple answer why is that the silicon used in the SunPower® cells is of a different type. SunPower uses n-type silicon and only p-type silicon found in conventional panels is effected by LID as it is boron-doped and suffers from the boron-oxygen effect when first exposed to sunlight. Yet another reason why SunPower is better.

Should I keep my panels clean?

The more sunlight that hits a panel, the more power it generates. Typically panels are self cleaning with normal rainfall. However, on your yacht, they are more prone to bird droppings and a build-up of general dust and dirt that does not wash off with just rain. Therefore, we recommend periodic cleaning of your E-Flex panels with non heated water, mild soap and a soft sponge to wipe the surface clean in a circular motion.

What is an MPPT charge controller?

MPPT stands for Maximum Power Point Tracking. This is to do with the solar charge controller that is highly recommended to have installed between your solar panel(s) and your battery bank. The MPPT charge controller serves to maximise the potential charge (amps) going to your batteries by constantly looking for the 'best' amount of power to provide. It does this by constantly monitoring the stage of charge of your battery bank and the output from your solar panels and adjusting the charge accordingly.

Another way to look at it is that the solar panels produce a higher voltage (18.8V) than the battery requires for charging (12-14V) and so the MPPT controller drops the voltage down and increase the amps. Depending on a number of factors this can increase the efficiency of your panels anywhere from 10-30%.

We have the Victron Energy SmartSolar MPPT charge controllers available in our store. We get a lot of positive feedback from customers that like the built-in bluetooth monitoring. That way from the VictronConnect app on your phone/tablet you can monitor the system in great detail.

Read our news story for more details on "Your MPPT controller & app explained"

Can I recycle my old solar panels?

A. Absolutely. As many fixed solar panels are now coming to the end of their lifecycle (20-25 years+) we are starting to enter a time where more and more solar panels will need recycling. This is the same for the newer flexible solar panels and it's important to recycle and keep solar panels out of landfill. SunPower has been committed to being a responsible producer and provides appropriate reuse and recycling options for their products. SunPower is a Founding Member and on the Board of Directors of PV Cycle for more info check out contact your local SunPower dealer or email us and we'll help you recycle your old solar panels.

Can you ship to me outside of the USA?

Yes. Although Sun Powered Yachts only offer domestic shipping in the USA it is possible to receive international shipping via a package forwarding company based in the USA. We recommend a company called who offering shipping to over 200 countries & territories. It's very easy to set up your own account with or please email us and let us know where you would like to have your SunPower E-Flex panels shipped to so we can provide you with a quote. Full details can be found on our shipping policy page.

Can I purchase the SPR-E-FLEX-170 panel in the USA?

The SunPower 170W flexible solar panel is assembled in France and has been available in the USA since March 2019. Order yours now! The 170W panel is subject to the solar import tariff when imported to the USA. This tariff is being placed on solar panels sized from 120W-320W. Read more on the new SunPower 170W from our recent blog post

I have a Watt&Sea, can I connect solar panels to my controller?

After chatting with the very helpful tech support at Watt&Sea we have the following info: Since 2014 the Watt & Sea hydrogenerator charge controllers can also receive solar input. The minimum PV voltage input is 7.5V, maximum PV voltage input is 50V & maximum amps input is 14A. So as long as you stay within these parameters you are OK. It is worth noting that the controller will only charge your batteries from one source at a time (hydro OR solar) NOT both at the same time. So when your hydrogenerator is not in the water/spinning to create hyrdro then it will recognize the solar input. An alternative option may be to install your own MPPT charge controller just for your solar panels. The Watt&Sea controller also has the ability to charge two battery banks (ie. your house bank and engine start battery) as long as they are the same voltage (both 12V or both 24V)

Will you ship my panels from Hawaii?

No. To help reduce costs and delivery time our stock of SunPower flexible solar panels is warehoused on the 'mainland' and we offer free shipping in the USA including Alaska & Hawaii. Free shipping also includes Puerto Rico, however for other US Territories (American Samoa, Guam, Northern Mariana Islands, US Virgin Islands) there will be an extra shipping charge. Full details are on our shipping page

Can I charge my 24V or 48V battery bank with solar?

Yes. Most solar MPPT charge controllers move power from higher voltage solar panel(s) to a lower voltage battery bank. These are called 'buck' controllers and the full range of Victron Energy SmartSolar MPPT charge controllers are 'buck'. So you need to have a solar panel array voltage that is greater than your battery voltage. The Victron MPPT controllers will auto detect what battery voltage they are connected to ie. 12V, 24V or 48V In contrast, if you didn't have the 'roof space' to have a large solar panel array then you may have a lower voltage panel that would need a 'boost' controller. This will take lower voltage solar panel(s) and boost it up to charge a higher voltage battery bank. A good example is the Genasun GVB-8 (boost) controller. If charging a 36V-52V nominal battery bank, the GVB-8 (Boost) controller is ideal with any SunPower flexible solar panel. Please check the spec sheets for detailed parameters or visit Genasun online

What is a conventional solar cell/panel?

A conventional solar cell is easily recognised by the thin metal lines that are on the front of the solar cell (cells on left of image) These thin metal lines are usually a cheap, aluminum paste which reflects the sunlight, covers the active solar surface of the cell & due to being porous is susceptable to moisture corrosion. This all contributes to the lower efficiency of the conventional cell which is typically around 15% SunPower cells by contrast are easily recognised by an absence of metal lines on the front and have a solid dark appearance (cells on right of image) There is nothing blocking the active surface as the contacts are allprotected on the back of the cell.

What does IBC mean?

IBC stands for Interdigitated Back Contact and refers to the unique design of SunPower solar cells (right of image) The IBC design means a solid copper foundation, found at the back of the cell, is where all the electrical contacts are. This eliminates the need for the metal lines on the front of the cell found on a conventional front contact cell.

How can I calculate Amps?

Use the magic triangle below to calculate Amps, Watts or Volts.

Watts = Volts x Amps (eg. 100W = 17.1V x 5.9A)

Amps = Watts ÷ Volts (eg. 5.9A = 100W ÷ 17.1V)

Volts = Watts ÷ Amps (eg. 17.1V = 100W ÷ 5.9A)

What does premium cosmetic quality mean?

At Sun Powered Yachts we only sell premium cosmetic quality panels. SunPower has different grades that are given to the finished E-Flex panels: Premium, High & Moderate. It's important to note that cosmetic quality has no effect on power production. In different applications customers may not be as concerned with cosmetic quality (eg. trucking industry)

Are these panels made in China?

No. SunPower is a US based company but the E-Flex panels are actually assembled in a SunPower factory in France. The solar cells are made in a SunPower factory in the Philippines.

What is Affirm and Sezzle?

Both Affirm and Sezzle are options at checkout that allow you to spread the cost of your purchase over a number of months with zero interest if it's paid off in full. We can also email you an invoice and then just select to pay with either Affirm or Sezzle. You then have to set up an account with them and you are on your way to enjoying clean & quiet solar power.

Can I mix solar panels of a different wattage, eg. 110W and 170W?

Yes you can, BUT it is not ideal and certainly needs more attention and thought before setting up. It is certainly better & recommended to wire together panels from the same manufacturer and the same panel wattage (or wire individual MPPT charge controllers) If you do plan on wiring dissimilar panels, you should know that: a) For series connection – the same current rating of the panels is more important b) For parallel connection – the same voltage rating of the panels is more important So as an example if you only had space for 1x110W panel on the dodger and 1x170W panel on the bimini then first I would recommend seperate charge controllers for each panel. If however you did want to go ahead and wire them together then you should look at the spec sheets and see if the current rating or voltage rating are more similar (closer together in value). The SunPower 110W is rated at 18.8V and 5.9A The SunPower 170W is rated at 29.4V and 5.84A As the current rating is very similar (0.06A difference) then in this example we would wire 1x110W & 1x170W together in series. However it's worth noting that performance will only be as good as the weakest link. So in this example both panels will only produce 5.84A - the current rating of the 170W panel, which is the lower of the two.

What does 'BATT', 'PV' & 'LOAD' mean on my Victron MPPT charge controller?

On the Victron Energy MPPT charge controllers you may see 3 pairs of positive & negative connections on the bottom of the controller. These are: BATT - Battery positive & battery negative PV - Solar panel(s) positive & negative LOAD - power to a 12V device positive & negative When wiring up your controller an easy way to remember the flow of power is "PV IN" & " BATT OUT" "PV IN" - Power comes from the solar panel(s) to the controller "BATT OUT" - Power goes from the controller to the battery bank. NOTE: We recommend installing a circuit breaker which would be on the positive wire from the charge controller to the battery bank. The LOAD feature is honestly something that very few customers will make use of. However, it does give you the ability to directly power something 12V from the charge controller. When combined with some of the features on the Victron Connect app it allows you to further control the settings of this LOAD feature. As mentioned very few people will use this however one example could be your anchor light. It's possible to wire your anchor light (positive & negative wires) to the LOAD connection on the charge controller and then by using the 'streetlight' feature on the app set the timer so that the anchor light will turn 'on' at sunset and turn 'off' at sunrise. Read our news story for more details " Your controller & app explained"

My electric motor has a high voltage battery bank, can I charge with solar?

Yes. We are confident that we can help you find a solution to charge your battery bank with SunPower solar panels. Some brands of electric motors require higher voltage battery banks eg 96V or 108V and your typical MPPT controller will only go up to 48V. We have worked on a few projects now with Elco and Torqeedo to find a solar charging solution. Please email us and we can help you with your project and in our shop we have a high voltage charge controller manufactured by AERL in Australia. An Elco EP-50 electric outboard requires a 96V (nominal) battery bank which requires a specific high voltage MPPT charge controller.

What are the SunPower E-flex panel warranty details?

No Salt Water Exclusion & Backed by SunPower 5-Year Power Warranty - SunPower also warrants that the power of the E-Flex PV Modules will be at least 80% of the Minimum Peak Power rating for 5 years. 2-Year Product Warranty - SunPower warrants that for 2 years beginning on the Warranty Start Date its E-Flex PV Modules shall be free from defects in materials and workmanship under normal application, installation, use and service conditions. If you are seeking a warranty claim from SunPower you can contact them directly: and include your panel serial number (found on back of panel) Otherwise contact us and we will be happy to assist. (For full details download the E-Flex warranty pdf from the home page)

Is this a manufacturer's warranty?

Yes. The warranty on the SunPower E-flex solar panels is from SunPower (the manufacturer) not Sun Powered Yachts (authorized dealer).

What is the panel 'nameplate'?

The solar panel 'nameplate' is the sticker found on the back of each SunPower E-flex solar panel. It contains all of the panel power specifications, as in the example below for a 100W panel, that you need to know when calculating your system size: Rated Voltage (Vmp) - 17.5V Rated Current (Imp) - 5.80A Open-circuit Voltage (Voc) - 21.0V Short-circuit Current (Isc) - 6.20A

Where can I find my panel serial number?

Each solar panel has a unique serial number that SunPower can use to identify the panel history; date of manufacture, panel testing results etc The first place you will likely see the serial number is a sticker on the outside of the boxed panel. There is a small sticker that you can peel off on the right hand side to keep for your reference. Otherwise each panel has a sticker with the serial number on the back of the panel, usually close to the nameplate. We suggest you make a note of the panel serial number(s) or take a photo of the sticker to keep as a reference should you need to contact SunPower about your panel they will ask for it.

What are interconnect tabs?

SunPower uses it's patented stamped tin coated copper interconnect tabs to connect each solar cell to it's neighbor. There are many advantages from the connection being on the back of the cells and so more protected and cooler. The built-in strain relief (small gaps) allows for expansion and contraction of the metal without breaking. This is called thermal cycling, the constant heating up and cooling down during the day as clouds pass over, shading etc. There are 6 points of contact for soldering, which gives a very good degree of redundancy should any one of them fail the panel will still work.

What does premium cosmetic quality mean?

At Sun Powered Yachts we only sell premium cosmetic quality SunPower E-flex solar panels. SunPower (the manufacturer) grades the finished panel depending on cosmetic quality. For some applications a lower cosmetic quality is acceptable, say the trucking industry, but for marine applications we feel it's best to only sell the premium cosmetic quality. These are the three grades from SunPower: Premium: Panels have minor blemishes and/or scratches, visible at <1m viewing distance High: Panels have minor blemishes and/or scratches, visible at >1m viewing distance Moderate: Panels have blemishes and/or scratches, visible at >1m viewing distance It's important to note that the cosmetic quality has no effect on the power production and performance of the panels.

What size MPPT charge controller do I need?

Have a look at our install page where you will find the range of Victron Energy SmartSolar MPPT charge controllers. Each has a max PV for the input, but it's important to look at some other parameters. 75|10 - $109.80 - PV Input: 12V - Up to 145W 24V - Up to 290W 36V/48V - N/A Feel free to email us and we can help size the correct controller for the number of solar panels and battery bank voltage you have aboard.

What does 'LINE' and 'LOAD' mean on my Bussman circuit breaker?

To keep it simple remember 'LINE' is in and 'LOAD' is out!! If you have a breaker between your solar panel(s) and controller then the postive cable coming from your solar panels goes onto 'LINE' then carries on from 'LOAD' to the PV+ on the MPPT controller. If you have a breaker between your charge controller and the battery bank then the positive cable coming from the BAT+ on the MPPT controller goes onto 'LINE' then carries on from 'LOAD' to the positive battery terminal.

Who is the ABYC?

The ABYC is the American Boat and Yacht Council, a voluntary standards creating body for the marine industry responsible for Standards and Recommended Practices. It's a great resource and we are proud to be a member, click here for more info on membership. Visit their website to learn more

What is a Bussman Series 187 marine circuit breaker?

A device that, like a fuse, interrupts a current in an electric circuit when the current becomes too high. Unlike a fuse, a circuit breaker can be reset after it has been tripped. When a high current passes through the circuit breaker, the heat it generates, causes a trigger to rapidly separate the pair of contacts that normally conduct the current.

How much power will I get from my panel?

There are more complicated ways to estimate how much power you are likely to get from your panel and performance will vary depending on weather conditions, shading etc. But to keep it simple you can follow this trick to get a potential daily yield in terms of amp hours (for a 12V system): For SunPower panels: divide the panel wattage by 3 For non-SunPower mono-panels: divide the panel wattage by 4 For non-SunPower multi-panels: divide the panel wattage by 5 So for the SunPower E-flex series of panels in a day and on a 12V system you could have a potential daily yield of: 50W divide by 3 = 16-17amp hours 110W divide by 3 = 36-37 amp hours
170W divide by 3 = 56-57 amp hours

What does my free consultation include?

After filling out some details on our website about your project and some key factors about the system you have/plan to have, we can look at which SunPower panel will work best and how many of them, recommend which MPPT solar charge controller to use aswell as the extra items needed to bring the whole solar system together. We will get back to you by email within 24-48hrs with some recommendations and a price quote for the total system. We may also include a wiring sketch, which will help identify how the parts of the system come together. We understand it's a lot of information to take in and read through and are happy to follow up on email or by scheduling a call with us. Of course we can answer any questions you may have, make any changes as necessary to the price quote and help you on your way to going solar with SunPower.

With my SmartSolar MPPT controller is the bluetooth always on/transmitting?

The Victron Energy SmartSolar range of MPPT controllers has built-in bluetooth capabilities. The bluetooth is always “active” drawing a very small amount of power and follows standard Bluetooth LE protocol.

After a period of inactivity the bluetooth goes into a low power search mode, less than 1mA. Once an external device queries it for connection (eg. your phone) it wakes up full functions again.

Should you prefer not to have the bluetooth feature then go ahead and choose a BlueSolar MPPT charge controller which has no built-in bluetooth. We don't list these in our shop but we can easily request one and email you an invoice.

Can I walk on the flex panels?

following the small print from SunPower the answer is no, however in reality you are OK to occassionally stand on the panels. These should not be placed in a high traffic area. Even the phrase walk on is some great marketing spin by other brands of panels that produce less power and they are looking at ways to differentiate their panels. In truth some of the 'walk on' panels with the non skid 'dimples' will in fact just end up collecting dirt or dried salt water which will further block the active solar surface and reduce panel performance.

Do you sell fixed frame solar panels?

Yes. As a SunPower Authorized Dealer we are the only channel that has available SunPower DC solar panels for sale to individual end customers to use on their boat or RV. Visit our Fixed Frame page for more info. Currently we are offering the 350W, 370W & 410W

Does 1% of my order go to charity?

We are pleased to collaborate with the Papahānaumokuākea Marine Debris Project and starting Febuary 1st 2021 1% of each order and invoice placed with Sun Powered Yachts will go directly to the PMDP. You are directly helping to protect the sensitive wildlife and critical habitats of the Papahānaumokuākea Marine National Monument (Northwestern Hawaiian Islands) from the threats of marine debris.

What is the Maxeon Air?

Maxeon Air is a new line of flexible solar panels that have a self adhesive backing. There will be a 330W panel and early production & testing is currently happening in France. More details on their website

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