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Solar Panel Store Blog — Solar Basics

Solar Mounts and Racking 101

Solar Mounts and Racking 101

To mount or not to mount?  No, that's not really the question when it comes to solar panels.  You pretty much have to secure them to something. The question is what solar mounting racks are available and how do you choose which one is right for you?


Solar panel type or construction will often drive your options for solar PV mounting structures. Most solar panels these days are rigid, aluminum-framed, tempered-glass covered silicon modules.  These types of solar panels will mount differently than thin-filmed modules which may be comprised of semi-flexible, plastic sheets.  Semi-flexible sheets can be glued to house roofs, RV roofs, boat decking, you name it.  They can handle curved surfaces well, and it's always nice to minimize holes in a roof.  If you're looking for a good adhesive, check out our Sikaflex sealant page.  Whereas, rigid aluminum-framed modules are designed to be clamped down to rails using special hardware and racking equipment described below.  Sometimes people will screw through the frames to secure modules to home-made racking or frames, but that method is more common for small backyard projects like pumps, etc.


Mounting solar panels to a residential or commercial roof is extremely common and a number of racking manufacturers offer solar panel mount solutions to fit most any type or pitch roof.  From ballast systems for flat residential or commercial roofs, to specialized fittings for asphalt shingle, standing-seam metal or clay tile roofs there is a solution for you!  While most roof racking involves securing an L-shaped "foot" to the roof surface, and securing horizontal "rails" to the feet, onto which solar panels are clamped, there also "rail-less" options as well.  Rail-less essentially involve attaching a set of feet to the roof and then securing a panel to a set of feet without rails.  Rail-less solar mounting racks are desired sometimes for aesthetics and for certain locations that make rails impractical. So should you mount solar panels to your roof?  Roof mounting is a great option when space or sunny options are limited.  And that's probably why most residential installations are roof-mounted.  Not everyone has enough sunny yard space to make a ground mount possible or desirable.  It also avoids the additional expense and effort to trench for longer conductor runs and set post or poles necessary when ground mounting. You’ll want or need (depending on your local building requirements) to inspect your roof’s structure engineering to confirm it can support a solar PV mounting structure.  Also inspect your roof's condition and make any repairs before installing a solar array.   Fire codes also often have set-back requirements to ensure the perimeter of the roof is accessible for firefighters.


Solar panel mounts for the ground arrays come in two flavors: fixed and "top-of-pole" mounts. Either offers some benefits over roof solar mounting racks.  Panels mounted on the ground will be cooler than on a roof, which helps maximize voltage and energy production a bit.  They are also more accessible should you have any issues--which is rare.  And some mounting options allow you to adjust the tilt of the array as the seasons change.   Ground mounts can be placed in optimal sun, tilt and orientation to generate the maximum energy.  Contrast to roof mounts that are usually flush mounted to the roof's tilt and direction (which is usually not ideal).  Both fixed and pole mounts will require trenching to run buried conductors, and digging proper foundations.  A fixed mount system may be a little more manageable as a DIY project.  And manufacturers like SnapNRack provide the design layout and parts akin to a tinker toy set!  That said, a pole mount may ofter the benefit of adjustability.   Pole mounts can also be combined with a "tracker" feature that rotates the array throughout the day to follow the sun.  Trackers can generate a bit more energy production than a fixed array.  But with low panel prices, we have found that the cost and maintenance (moving parts break) can be offset by just oversizing your array by a panel or two.

RV & Boat  

Mounting solar panels on an RV roof or boat roof or deck is usually a little different than for typical residential or commercial roofs, so we have a separate page for solar panel mounts for RVs on our site.  We already discussed adhering semi-flexible panels above.  Rigid solar panels are individually mounted to an RV or boat roof using a set of Z-brackets, or to a tilt-mount bracket or a set of corner molded brackets glue to the roof and in turn screw into the aluminum frames for a rock solid mount.  We also have a nice Go Power Cable Entry Plate that mounts over the roof hole and neatly connects to all solar panel leads--nice and clean.


There are many types of industrial, farm or other remote power installations where 1-2 panels need to be mounted near the remote equipment (like pumps, lights, sensors, monitors, other instruments).  So our Side Of Pole page shows a variety of solar panel mounts that connect to an existing pole.  Typically a battery box can be mounted on the same pole to house the battery,  charge controller and wiring. Many of these solar mounting racks can also be screwed into a horizontal wall (like a shed for example) and can be tilted as well.  Often the less expensive mounts work best for 36 cell, 12 volt panels.  But there are options for the larger 60 cell panels as well.

Mounts and Racking Products.

Check out our Solar Mounts and Racking.  We'd be happy to help you  find the specific mounting solution to fit your needs.  Give us a call!
Charge Controllers 101

Charge Controllers 101

Do you need a solar charge controller?

If your solar PV system will require batteries, then YES! If not, you can skip right on by this page. Why? Because solar charge controllers control or regulate the charging of batteries in a battery-based solar PV system. And because most residential solar electric systems are “grid-tied” systems, they do not use batteries and thus have no need for solar panel controllers. But all the off-grid homes and remote equipment power by solar-charged battery systems (lights, sensors, instruments, etc.) need charge controllers to safely and efficiently charge their battery investments.

Victron Charge Controller

What do charge controllers do?

Didn't we just cover this? Kind of. But let's get a little more specific. You may wonder why these devices aren't just called battery chargers? Generally speaking, a battery charger refers to a device that you plug into an AC outlet and then connect to a battery to charge it. You may have one in your garage to charge the car battery when dead. A charge controller is used to regulate the voltage and current coming from a DC energy source like a solar PV array. It sometimes helps to think of these as solar charge controllers or DC charge controllers, especially if your system may also include an inverter/charger (mentioned on our Inverter page). In that case you would still need both the inverter/charger (which involves AC charging of the battery bank) and a DC solar charge controller to regulate the flow of solar DC energy into the batteries.

Charge Controller - Water Faucet  Analogy.

The goal in charging a battery is to bring the battery's voltage up to a factory-defined level that represents its full charge. A classic analogy will illustrate how solar charge controllers work. Imagine you want to fill a glass from a water faucet. Think of the faucet as the charge controller and the glass as the battery. The water level in the glass represents the battery's voltage level.  The water flow represents the current.  As long as the water level is low enough, and the flow of water slow enough, then the glass will accept more water. Just like a low battery will accept DC current. But turning the faucet wide-open will quickly overflow the glass from the force of the water flow. Similarly, without a charge controller, excessive DC current flow can overcharge the battery.  But adjusting the faucet, reduces the water flow to more steadily fill the glass without spillage. Likewise, a charge controller controls regulates the DC current flowing into the battery to steadily raise the battery's voltage to effectively and efficiently re-charge the battery without causing damage.

Battery Charging Set points. 

More specifically, a charge controller regulates current into the battery by based on charging "set points" for that battery.  Battery manufacturers specify certain voltage levels ("set points") for each of the 3 stages of battery charging. There is a set point for the bulk, absorption and float charge stages that solar panel controllers keep track of. So a depleted battery is like that empty glass. The charge controller feeds the the highest current (like the fast water flow of an open faucet into an empty glass) during the bulk stage until the voltage level rises to the bulk stage set point at which point the battery is about 80% recharged. At that point, the charge controller reduces current (or flow) like a slow-running faucet until it reaches the absorption set point. After that the charge controller basically just drips enough current to keep the battery voltage at its float set point (filled to the brim).
What kind do I need?
There are two types of charge controller technology used these days. The cheaper, effective but more limited PWM or pulse width modulation charge controllers are one type.  While MPPT or (maximum power point tracking) charge controllers are the more efficient and flexible, but more expensive type.  On our website, you'll find PWM charge controllers under the Small Charge Controller page, but you'll find MPPT charge controllers on both the Small Charge Controller and Large Charge Controller pages.  We define Small Charge Controllers to generally be those up to 30 Amps, and Large Controllers above that.

PWM Charge Controllers.

In the typical scenario, we look to see if we can simply match the voltage of the controller to your battery bank. So a 12 volt controller matches with a 12 volt battery bank/system. This is the typical situation with an RV or boat. Similarly, if you have a 24 volt battery bank for your off-grid house, you would match it with a 24 volt charge controller. Same for 48 volt systems. In these scenarios, the cheaper and perfectly good choice would be a pulse width modulation (PWM) solar panel controller. Huh? We'll explain in a minute. Contrast the PWM controller with a maximum power point tracking (MPPT) charge controller. The MPPT controllers cost more, but allow you to use a larger voltage solar panel/array with a smaller voltage battery system. So a 60 cell, 30V solar panel can charge a 12 volt battery bank when an MPPT controller is used.

MPPT Charge Controllers.

An MPPT charge controller feeds the maximum amount of energy produced by the solar array to the battery bank. Voltage may vary from the solar array depending on the sun's intensity. But despite that, an MPPT charge controller can use all of the available energy to charge the batteries Why? Since watts = voltage x current, an MPPT controller can adjust the voltage to match the battery by adjusting the current. This also allows an MPPT controller to use a larger voltage solar array than the battery bank uses. So while the MPPT controllers cost more, they get more charging bang, for the solar array buck. Conversely, a PWM charge controller can only use the voltage supplied by the solar array that matches the battery bank voltage to charge the battery bank . So when panels produce more voltage in better sun and/or cooler temps, the PWM controller can only use up to its rated voltage to charge the batteries--which may mean energy wasted. Similarly, a PWM controller cannot use a higher voltage solar array (say 30 volts) to charge a 12 volt battery bank. But a PWM does a very nice job charging batteries if its voltage is in sync with the battery bank. In the same way pulsing a faucet on and off in quick small bursts get a glass of water nicely full, a PWM controller charges a battery by pulsing quick small bursts of solar energy.

Click here to see our charge controller product lines or drill down into specific types in the menu above. 

Inverters 101

Inverters 101

Solar Inverters.  

If you're exploring the idea of going solar, no doubt you've heard that solar inverters are essential components for most solar electric systems.  Buy why is that?  Why are solar inverters so important? And what does a solar inverter do anyway?  Are all inverters the same? This page’s focus is to layout some of the basics involved with the different types of inverters and try to answer some of these questions along the way.  

What is an inverter? 

As you probably know, there are two forms of electricity commonly used today.  Solar panels produce the form known as direct current (or DC) electricity.  DC is also the form of electricity most batteries store.  On the other hand most homes and businesses use alternating current (AC).  AC faces less voltage drop over long distances, making it a convenient form to move from power plants to end users.  An inverter's main function is to invert DC electricity into AC electricity.  Inverters span a range of sizes, from small ones that allow you to run your laptop off your car's cigarette lighter, to larger and more robust inverters designed to work with home or industrial solar electric systems.  But there really isn't a generic solar inverter.  Why? Because there are different types of solar electric systems, which require different types of solar inverters.

Grid-direct inverter.  

A grid-tied or grid-interactive solar electric system is the simplest solar system and requires a specific grid-direct inverter.  In a typical residential grid-tied system, the solar PV modules send DC current to the grid-direct inverter, which inverts the DC electricity to AC and then sends the AC to home's electric service panel to feed any electricity demand in the house.  If the current house loads are less than the AC output from the inverter (like in the daytime when no one is home), the grid-direct inverter routes the electricity back to the utility (causing the meter to run backwards).A grid-direct inverter must produce a clean, pure "sine-wave" of AC electricity that matches the utility grid's wave form.  What's a sine wave?  An alternating current electrical wave has the shape of a sine wave.  If you see an inverter spec sheet that says  "modified sine wave," then you know that inverter cannot replicate the utility's form of electrical wave.  That means that some devices will not function (or at least not as well as they could) on electricity from a modified sine wave inverter.  Today, essentially all grid-direct inverter replicate's the grid's sine wave shape.Grid-direct inverters must also comply with UL-1741 anti-islanding safety requirements of the NEC (National Electric Code).  "UL" means Underwriters' Laboratories.  The applicable NEC provision requires that when the utility grid goes down, a grid-direct inverter must automatically disconnect the PV array from the electrical system.  This is a safety requirement to help ensure electricity from the PV array doesn't flow back onto the utility lines and injure any utility workers repairing the lines during a power outage.  This also means that while the solar panels may be producing power during a day-time power outage, the inverter stops the supply of electricity to the house.

Stand-alone, off-grid inverter.  

A stand-alone inverter need not concern itself with the grid because it is only used in solar electric systems where there is no grid electricity present.  In this situation, the PV array supplies DC electricity to a DC charge controller that charges a battery bank. When the house demands electricity while the sun is shining and the battery bank is full, the stand-alone inverter tells the charge controller to skip the battery bank and route the DC electricity from the solar panels straight to the inverter which then supplies AC electricity to the house loads.  When the array isn't producing (at night), the  inverter inverts DC to AC electricity that is stored in the battery bank via the charge controller.  Today, most off-grid inverters are really "inverter/chargers" because they also include the functionality to allow charging of the battery bank from an AC source (usually a generator). Why?  Because unfortunately, the sun doesn't shine all day, every day in most places.  After more than a few days without good sun (clouds, rain, snow), the batteries discharge to their limits and can't be fully charged by the solar panels.  Connecting a propane or gas generator to the inverter/charger inputs allows for convenient recharging of the batteries.  Some inverter/chargers even automatically start the generator when the inverter senses the need.In the past it wasn't uncommon for off-grid inverters to produce a lower quality wave like a "modified sine wave" or a "square wave" since there was no need to match the utility's  wave form.  But technology has improved and to ensure AC loads in the house or business are appropriately powered (especially today's sensitive electronics), off-grid inverter/chargers commonly produce clean sine-wave electricity.

Grid-Tied with Battery Back-up.  

A grid-tied with battery back-up solar electric system combines components and functionality of a grid-tied system and a stand-alone battery-based system.  As a "hybrid" system, it is the most complex system with the most components.  The inverter for this system is also more accurately called an inverter/charger because it can connect with an AC source to charge the battery bank when the sun can't do the job.  But in the case of a hybrid system, the utility grid is present so the primary AC source used to charge the batteries is the grid.  Some models allow a secondary AC source (a generator) to be connected as well.  Like a grid-tied inverter, this hybrid inverter also sends excess solar-produced electricity back to the grid (as long as the batteries are fully charged).  And when the grid goes down, the hybrid inverter disconnects from the utility grid (like a grid-tied inverter does) and pulls DC electricity from the battery bank, inverts it to AC and sends to a special "emergency" or "back-up" load center or panel.  To avoid excessively large and expensive battery banks, a home owner must be selective and only choose important loads to be backed up.

String vs Module level inverters. 

For grid-tied solar electric systems, there is another choice to be made.  Do you want a single "central" inverter to which all strings of solar panels connect?  Of do you want to attach an individual "micro inverter" behind each solar panel that inverts DC to AC at the panel?  Or do you want a hybrid style central inverter connected to DC optimizers attached to each solar panel?  How to choose?

String inverters.  

String inverters are the original workhorse style of the solar grid-tied inverter. These types of inverters are tried and true.  And today, they are generally cheaper than module-level micro inverters or DC optimizers.  They do lack the ability to optimize and "maximize" the power produced from each solar panel.  And they also can't reduce the impact one shaded or impaired panel may have on the array's production.  For example,  shade on one panel may reduce the production of the entire string of panels in that array. A string inverter can maximize power production of an individual string but not at the module level.


These devices are little mini inverters that attach behind the module and invert from DC to AC at the module level.  This means that that AC wiring connects the solar array to the house,  which is cheaper and less subject to voltage drop than DC wiring.  But more importantly, having a mini inverter connected to each module means that each module can be adjusted to produce the maximum amount of power possible (called maximum power point tracking or MPPT).  So if one panel is shaded, it does not reduce the power produced by the string In general, microinverters should produce a bit more power than string inverters, which is a good thing!  Finally, for some of us, our inner geek appreciates the ability to monitor individual panel production on our home laptop or phone. But beyond satisfying our curiosity, monitoring also makes it possible to quickly fix or replace any components minimize downtime.

DC Optimizers. 

These types of inverters are a bit of a hybrid. Like a microinverter, a DC optimizer attaches to the rear of each solar panel.  And they enable maximum power point tracking (MPPT) for each panel as well.  But the module-level optimizer doesn't invert to AC at the panel.  Instead each optimizer connects back to a central inverter where AC electricity is actually produced. These devices can be a bit cheaper than a true microinverter while providing  similar benefits.

Solar Inverter Pages.  

Hopefully this introduction has helped you become a bit more familiar with the terminology and the  choices available for solar inverters.  Check out here or drill down in the  menu above.  Give us a call so we can help get you the right inverter for your project
Deciding on the Best Solar Panel System for your RV

Deciding on the Best Solar Panel System for your RV

RV Solar Panels

Shopping for RV solar systems can be a drag if you don't have the right knowledge on what you will need for your situation. Solar panel mounting tends to be difficult if you've never done it before but we're here to help you along every step of the way.

Steps to deciding on the right solar system for Rv's

1) Decide what kind or RVer you are 

First off, you will need to categorize your RV usage - that is, are you a full-timer? Or are you someone who just gets away for the weekends? If you fall in either of these categories, you'll want to really do the math before investing in a solar panel system. But if you're someone who tends to go away off the grid for extended periods of times but you're not a full-timer, then you should consider one of our solar electric systems. Why is this the most likely scenario where your investment will really pay off? Because the weekend warrior will always have enough battery to get through the weekend. And full-timers will most always find somewhere to doc where power is supplied at the RV park, and you're going to end up paying for that electricity anyway with your park fees. Same goes for marine solar, you need to ask yourself whether you'll have shore power or if you'll be spending extended periods on the water without a generator.

2) Decide how much solar power you will need

Electricity consumption differs from user to user. For example, if you have a larger RV with a microwave, TV, lighting, water pumps and electrical hookups for other devices, you'll need a different RV solar kit than someone who has a smaller RV that needs to run less lighting and perhaps only a water pump. So figure out how much power you'll consume in (example, 4 hours of TV might take 600 watts/hours per day, lighting = 350, refrigerator = 5,000). Then you'll need to know how much storage or battery capacity you'll need on board. From there, you'll be able to back into the numbers and get the proper setup.

An example might be needing to generate 2,000 watts per day so a nice 400 watt system would be the perfect system for someone who needed to power enough to use for that day on into the evening. Of course if you travel when you know you won't have full days of sun and some cloudy days, you'll probably want to increase the capacity for charging. It won't be too long that you'll break even after looking at a gasoline powered generator running to generate that kind of power, not to mention the impact on the environment.

3) Decide on the RV solar system or Marine system you'll need

Based on the few tips above, we'd love to help you decide on exactly what you need. Just give us a call and we'll gather your requirements and help you find the perfect, tailored solution to your portable solar panel needs.

RV Solar Kits