Author: Cheyenne Minard

Best Solar Inverters for Grid-Tie Systems (2019 Edition)

Best Solar Inverters for Grid-Tie Systems (2019 Edition)

What are the best solar inverters in 2019?

We recently published our recommendations of our favorite off-grid inverters you can buy for solar applications.

It quickly became one of the most popular articles on our site. So now we’re back with its counterpart: a review of the best solar inverters you can buy for grid-tie systems in 2019.

These are the inverters you would use in a traditional home or office system – any property that has access to power lines and can connect to the utility grid.

We put together a video to highlight our picks. You can also keep reading for more detailed analysis, current prices and key product specs.

Here’s our review of the best grid-tied solar inverters you can buy on the market in 2019:

Best Grid-Tied Microinverter

Best String Inverter with Optimizers

Best Grid-Tied String Inverter

Best Storage-Ready Grid-Tied Inverter

Why Do I Need an Inverter?

If you’re just getting into solar, let me quickly explain what an inverter does.

The inverter is like the brain of your solar system. It manages the flow of power throughout your system.

When panels collect energy from the sun, they generate DC (Direct Current). But home appliances use AC (Alternating Current).

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At its core, the inverter has a simple job: it converts captured DC power into usable AC power.

Beyond that basic functionality, some inverters have extra features that make them more suitable for specialty applications. Let’s take a look:

Best Microinverters for Grid-Tied Systems: Enphase IQ7+

  • Price: $158 apiece, which includes a mandatory Q cable for each panel. Total cost comes to 54 cents/watt.
  • Wattage: 290W
  • Peak Efficiency: 97.6%
  • Individual Panel Monitoring? Yes
  • Best for: starting with a small system and expanding in the future. Also great if you have multiple places to build on your roof and want to split the system into sub-arrays.

The concept of microinverters is simple: pair an inverter with every panel.

The benefits are fairly easy to understand as well. There are two cases where you should use microinverters:

  1. You want to start with a small system and be able to expand down the road.
  2. You want to monitor each panel independently.

In some ways, when you pair a microinverter with a panel, you’re creating a self-contained single-panel solar energy system. Each will produce power regardless of how many panels you have.

We recommend the Enphase IQ7+ Microinverter for these applications. As of the time of publication (January 2019), these are $142 apiece. You also need a mandatory Q Cable for each microinverter, which adds $16 per panel.

You would pair them with a panel ranging up to 300 watts, which will cost you another $150-$225 or more depending on panel selection.

Each inverter and panel pairing works out to around $350 (fluctuating by ~$50 depending on which products you pick). This does not include the cost of mounting or wiring the system.

Recommended Panel Pairings For The IQ7+:

Astronergy 335W or Mission Solar 310W

So how does the math look when you’re trying to build a full-sized system?

Let’s say it would take a $10,000 system to completely offset your energy bill, but right now, your budget is only $3,000.

If you want to cancel out a portion of that bill right away, you might get about 8-10 panels with microinverters on them. You’d start saving money on electric bills right away, and you can easily add on to it a few years down the road until you hit your target of 100% energy offset.

The ease of installation is another nice side benefit. Microinverters use standard AC wiring, which is cheaper and easier to work with.

In all, microinverters make it possible to get started with solar and build out your system at your own pace. But that scalability comes at a slightly higher price than other options.

If you have the budget to build a complete system from the start, we’d recommend going with a more cost-effective option: a string inverter.

Best String Inverter: SMA Sunny Boy

  • Price: $1725 (22 cents/watt)
  • Wattage: 7700W
  • Peak Efficiency: 97.5%
  • Individual Panel Monitoring? Not by default (you can add optimizers for extra cost, but you lose the Secure Power Supply feature by doing so.)
  • Best for: complete grid-tied systems in full sunlight.

A string inverter is a single unit that hooks into a string of solar panels. Our recommendation in this category, the SMA Sunny Boy, is sized to support strings in the range of 6-14 panels.

String inverters are your least expensive option, and they thrive in the right conditions.

The main issue with string inverters is that when shade falls on one panel, the efficiency drop translates to the other panels in the string. So if you have 10 panels in a string, and one gets shade, all 10 will drop to the reduced output of the shaded panel.

But what if you have space to build a system that will never fall under shade?

If you have land with plenty of unobstructed space, this is going to be the cheapest and most effective inverter for most systems.

If you live on a city block with buildings or trees casting shadows on your panels…not so much. You’d never get close to the expected output from your system.

But if you’re sure you have enough room to build away from obstructions, go with the SMA Sunny Boy inverter. It’s a reliable string inverter that is far cheaper than other options assuming you meet the requirements.

Depending on the model, the Sunny Boy inverters have either 2 or 3 inputs, which means you’ll have either 2 or 3 strings of panels wired to your inverter.

The SMA Sunny Boy also comes with a neat feature: a 2000 watt Secure Power System (SPS). The SPS is a feature unique to the SMA brand.

The SPS acts like a small backup power source in case of outages. While it’s not a long-term solution, the SPS powers a dedicated 120v outlet that can power up to 2000 watts during the day if there is solar power available.

You can also buy optimizers and pair them with the inverter. This will help mitigate the shade problem, but as a tradeoff, you lose the SPS functionality.

It makes sense to add the optimizer if you previously built an SMA system, then needed to retrofit the array due to new obstructions. Adding optimizers onto the panels would be easier and more effective than ripping out and replacing your whole inverter.

However, if your goal from the start is to get the most output from a partially-shaded array, we would recommend a different inverter for that purpose.

Best String Inverter w/Optimizer: SolarEdge HD-Wave

  • Price: $1875, plus mandatory P400 optimizers at $67 per panel. Works out to 42 cents/watt for a 24-panel system.
  • Wattage: 7600W
  • Peak Efficiency: 99%
  • Individual Panel Monitoring? Yes
  • Best for: a broad variety of grid-tied solar applications. You get the convenience of centralized design, paired the flexibility of panel-level monitoring. It’s the best mix of features and price.

Our best-selling residential grid-tied inverter is the SolarEdge HD-Wave line, a string inverter with optimizers. The classic HD-Wave line received a major update in 2019 with the introduction of the SetApp feature, which allows you to program and monitor your system from a phone app (rather than on the LCD screen).

This is our go-to grid-tied inverter option because it offers the best of both worlds. You get the lower cost of a central string inverter combined with the individual panel monitoring offered by microinverters.

For that reason, it works in a broad range of applications. In most cases, it’s simply the best combination of features and cost you can find in a grid-tied inverter.

The system is shade-tolerant thanks to the optimizers attached to each panel. And it’s cheaper than microinverters once you scale to at least 8 panels (the minimum string size compatible with SolarEdge inverters).

In the end, SMA and Enphase are tailored to a specific application. The SMA Sunny Boy needs full sunlight, and Enphase microinverters are more appropriate if you start with a small system.

For other grid-tied applications, our default recommendation is the SolarEdge line. It’s the workhorse of the industry: nothing too flashy about it, just versatile, reliable and easy to use.

Our most popular size is the SolarEdge 7.6 kW HD-Wave inverter, but they come in a range of 3.0 kW to 11.4 kW options for residential systems, with higher capacity options available for commercial use.

Best Grid-Tied Inverter With Storage Capacity: Outback Skybox

  • Price: $6,445
  • Wattage: 5000W
  • Peak Efficiency: 97%
  • Best for: grid-tied systems with energy storage, which protects against power outages and allows you to store power and use it later.

If you want to add battery backup to the mix, you’ll need a storage-ready inverter to manage your system.

Aside from protecting against emergency outages, energy storage has another purpose. You can take control of your power, storing it for later or sending it into the grid.

This is used in areas where the utility bills have time of use (TOU) charges or residential demand charges. Energy storage allows you to store and consume the power your generate. You can even sell excess energy back to the utility for a profit.

Our recommendation in this category is the Outback Skybox. It’s our favorite battery backup option because it checks all the boxes:

Ease of Installation

All components (inverter, remote control, breakers/load center and PV inputs) are included in one unit. Since all connectors for the PV array, the utility grid, and a backup generator are present in the main console, you only have to mount a single unit during installation.

This makes it far easier to install than other systems, which require you to mount and wire anywhere from 3-6 different components together for interconnection. The ease of installation is one of the Skybox’s key selling points.

Battery Flexibility

It works with any standard 48V battery bank. It’s more flexible than the competing StorEdge option from SolarEdge, which is only compatible with a single battery (the LG Chem).

Backup Generator Input

It has an input for a backup generator, in case you need to build a hybrid generator + solar system.

Works Without Batteries As a Standard Grid-Tie Inverter

It allows you to start as a pure grid-tie system and add batteries later without any additional parts or configuration changes. Other products don’t have this flexibility. Outback’s own Radian system requires you start with batteries, and the Magnum MicroGT will require additional components if you choose to expand into energy storage.

The Skybox’s versatility makes it our preferred pick for energy storage systems.

An Alternate Energy Storage Pick: Magnum MicroGT

Another good pick for storage-ready inverters is the Magnum MicroGT. It provides backup power like the Skybox does, but in micro-inverter form.

However, the MicroGT lacks the functionality to offset time-of-use charges and sell energy back to the grid. It also does not comply with the new smart inverter requirements in California and Hawaii.

These drawbacks prevent us from recommending the MicroGT all situations. The Skybox is simply a more complete and versatile product.

This article was updated on 2/13/2019. For our most current prices, take a look at the inverters page in our shop.

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8 Costly Solar Mistakes to Avoid When You Design Your System

8 Costly Solar Mistakes to Avoid When You Design Your System

Today we’re going to look at the most common mistakes we see from beginners who are just starting to research and design their own solar system.

Our goal with this article is to prevent common headaches and (potentially costly) problems that stem from poor system design.

Since we came online in 2002, we’ve talked to tens of thousands of people about going solar.

Many of those calls start the same way: someone’s just had “the epiphany.” They realized solar power not only helps the environment, but is actually cheaper than paying the utility company in the long run.

Sometimes, people are so eager to get started that they dive in headfirst. They research products, calculate a cost estimate, and start sketching panel layouts for their roof.

But solar system design is a lot more complex than it appears on the surface.

So when people try to design a system without doing the research, they sometimes make mistakes. Big, glaring, expensive mistakes.

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I touched base with a few of my colleagues to brainstorm the most common solar mistakes and misconceptions people have when they first get in touch with us.

Here are the points that came up over and over again:

1. Confusing off-grid and grid-tie solar

Solar power allows you to generate your own energy, which means you won’t pay for power from the utility grid. People assume this means they will be “going off the grid,” but that’s not accurate.

In reality, most people are looking for a grid-tied solar system.

Here’s the distinction: your panels generate energy, but you need a way to store that energy for later use. If you have access to power lines, you can store the energy you generate in the utility grid. The utility company will credit you for extra power produced, and allow you to pull from the grid when you need it.

Off-grid properties have no access to power lines, so they need another method to store energy. That means off-grid systems need a battery bank to function. Batteries are expensive, but with no option to store power in the grid, they are mandatory for off-grid systems.

The bottom line is that saving money and being independent from the grid are mutually exclusive. Batteries eat into your ROI (return on investment), and grid-tied properties don’t need them.

You don’t need to go “off the grid” to get the benefits of solar power. If your property has access to power lines, grid-tied solar is the smartest option.

Why pay for batteries when the utility grid will take care of storage for you?

Related: Grid-tied vs. off-grid solar: Are you sure you want to live “off the grid?”

2. Improper system sizing

Sizing a solar system is more complex than it appears at face value.

If you’re just starting out with your research, you might think it’s as simple as looking at your latest energy bill, then buying enough panels to cover that usage.

But that would ignore factors like climate, panel orientation, shading, natural efficiency drop, and other things that impact the “true” output of your system.

That’s why we won’t sell complete systems to anyone until they’ve consulted with one of our in-house solar design techs.

During that conversation, we plan your system to account for the variables most people don’t think about. Some common ones are:

Efficiency

Panels have an efficiency rating, and they suffer a 0.5-1% efficiency drop every year. 20 years after you install it, your panels will be 10-20% less efficient. We design a bit of extra headroom into your system to account for the loss of efficiency.

Climate

Solar panels are tested in ideal conditions: an indoor factory with temperatures in the mid-70s. In the real world, your system can be exposed to much harsher conditions. High temperatures can reduce the amount of energy you generate.

Your location also dictates how many sun hours you get. The term “sun hours” doesn’t mean “how long the sun is in the sky.” It refers to the amount of time the sun is in the right position to generate peak energy. Most places get 4-6 sun hours per day, and the exact amount influences system sizing.

Voltage

Inverters and charge controllers have maximum and minimum voltage input windows. Panels and batteries have a voltage rating as well.

Your system needs to be designed at the right voltage based on the equipment being used and what it requires. We also account for things like temperature that can affect voltage and system performance.

If you don’t have the right voltage from your solar panels or battery bank, your system might not perform well or worse – you could damage expensive hardware.

Battery bank sizing

Mismatching your battery bank with your charging source is the most common issue when it comes to batteries, specifically with off-grid system sizing. Your array needs to supply enough power to keep the batteries charged, but not so much that they overcharge.

Too much current could damage your batteries from overcharging. On the other hand, undercharging your batteries can have an even worse effect.

Certain batteries need to be brought up to full charge on a regular basis. Leaving them at empty or partial charge for an extended period of time can cause the batteries to fail prematurely.

3. “Solar prevents power outages!”

You’re generating your own energy, so the lights should stay on during a power outage, right?

Unfortunately, that’s not the case with grid-tied solar systems. Although the power originates from your panels, it is still stored in the public utility grid.

When the grid power goes out, so does yours, because there’s no infrastructure to feed that power to your property.

The remedy for this is a grid-tied system with battery backup. When the power’s on, it functions like a normal grid-tied system. During an outage, a small backup battery bank kicks in to keep the lights on.

It costs a bit more, but the peace of mind is invaluable, especially if you live somewhere with extreme weather conditions or unreliable power from the grid.

4. “Solar is a bad investment” / “Solar isn’t feasible without the tax credit”

Look, solar isn’t cheap. It’s a 4 to 5 figure investment. We know that’s a big commitment.

But electricity from the power company isn’t cheap either, and it’s only going up in price.

The reality is when you look at the long-term value of owning a solar system, most grid-tied systems pay for themselves fairly quickly and actually make you a profit over the life of the warranty.

We explain how to calculate your payback period on our resource center page about the ROI of solar. But here’s the quick version:

Let’s use a system that costs $10,000 (to make the math easy). That would get you something like this 6.6kW system.

You get a 30% tax credit for going solar, so the out-of-pocket cost is $7000.

$10,000 – $3,000 = $7,000

A 6.6 kW system will offset around 900 kWh of energy usage per month. At a typical rate of 12 cents per kWh, that’s a utility bill of $108 per month.

900 kWh * 0.12 = $108

To calculate payback period, multiply this bill by 12 to get your annual energy savings (in this case, $1296). Divide that number into your system cost to calculate your payback period, the time it takes for your system to pay for itself entirely.

$7,000 / $1296 = 5.4 years

This system will pay for itself in about five and a half years. Most solar panel warranties last for 25 years, and inverters for 10 years. After you clear the payback point, your solar system starts to turn a profit for you.

This assumes you perform a DIY installation. If you hire an installer, you might pay them $1 a watt to set up your system. That would make your system cost $16,600 before the credit, and $11,620 after the 30% back. The math changes slightly:

$11620 / $1296 = 8.96 years

A 9-year payback period on a system with a 25-year warranty. Still not bad at all.

“But the tax credit is going away in 2022!” Yup, that’s true. And we hear people say subsidies are the only reason solar makes sense.

So just for fun, let’s try it one more time without the tax credit:

$16,660 / $1296 = 12.8 years

We’ve gone from 5.4 years to 12.8 years by hiring an installer and skipping the tax credit, and we’re still paying off the cost halfway through the life of the system.

Solar costs a fair bit of money up front, but no matter how you slice it, grid-tied solar can pay for itself long before the equipment wears out. The more expensive your power rates are, the quicker the payback period and ROI.

5. Leasing

Solar power is a sound investment…if you own your system.

When you lease your system from a third party through a Power Purchasing Agreement (PPA), the value of that investment pretty much vanishes.

We can think of a few reasons why leasing is a bad deal.

The first thing to understand is the lender owns the system, which means they’re eligible to claim all the incentives. You won’t see a penny from the 30% federal tax credit or any local rebates.

After you’ve been squeezed out of the incentives, you’ll also pay a premium rate to lease the panels, which includes interest. In all, you might find you paid twice as much to lease the system as it would cost to finance and own the system yourself.

Leasing also makes it more challenging to sell your home. You have to transfer the lease to the buyer upon sale. Or, you can pay off the remainder of the lease balance and add that amount to your asking price. Both options limit the pool of potential buyers for your home.

We explain more about why we think leasing is a bad idea in our article: Should you Buy, Lease or Loan?

6. Not planning ahead

I brought up the fact that most panels are warrantied for 25 years. That’s a long time to go without any big changes in your life.

When people start planning their system, everyone thinks about what they need right now. Not as many people think about how their needs will change in the future.

What happens when you have kids, build a new workshop, or buy an electric car that needs charging? You’ll start consuming more energy. So we always tell people to look to the future when you start planning your system.

Some things to think about:

Do you have space to expand the installation if necessary? For example, say your system takes up your whole roof. What happens when you want to add panels later but have nowhere to put them?

Is your system designed to be expandable? People often think, “hey, I’ll just add more panels!” without realizing the other parts of the system, like the inverter, need to be sized to match. Central inverters have a limit to the number of panels they can support, so it’s often not as simple as “just adding panels.”

Micro-inverters are a great option to facilitate expansion for grid-tied systems. They work on a one-to-one basis: each panel is paired with its own micro-inverter. When you want to add on, just pair another inverter / panel pairing and mount them onto your array.

For off-grid properties, you should also think carefully about battery sizing. Depending on the battery type and age, it might not be possible to expand your existing battery bank.

Lithium battery banks can be expanded, but lead-acid batteries have limited options for increasing storage capacity.

The reason? When you add new lead-acid batteries to an old bank, the new batteries absorb the characteristics of the old ones. The new batteries are essentially being aged prematurely.

Lithium batteries are the exception. They have an integrated circuit controlling the charge parameters. The old batteries charge independently from the new ones, so you don’t run into the same issue.

7. Overpaying for installation

When you start to think about going solar, the first option that comes to mind is a turnkey installation from a national provider like Tesla, Vivint, Sunrun, or SunPower.

They offer an all-in-one solution to design your system, source your parts and install it for you. You can’t beat the convenience, but you also pay a premium for the catered experience.

Turnkey installers charge you anywhere from 100-200% of the cost of equipment to install your system. For a system worth $10,000 in equipment, they may charge another $20,000 to install it.

Big solar installers need to charge this premium to cover advertising, office rent, insurance, labor, and other expenses required to run their business on a national scale.

What many people don’t realize is that you can buy packaged solar systems from a wholesale distributor, then build it DIY-style or bring on a local contractor to help with part of the installation.

Working with a local contractor can save you a lot of money if you are willing to organize the project and take on some of the easy tasks. To help you find a local contractor to guide you through your project, we wrote an article about how to find a solar installer you can trust.

If you do choose to take on the project yourself, we also recommend fielding quotes from multiple installers before you choose the one you’re comfortable with. Contractors charge quite a broad range of rates, depending on their specialty as well as the complexity of the project.

Even a rate difference of 25 cents per watt can change the bid by a couple thousand dollars. It’s smart to use a service like Solar Power Rocks to compare quotes from local installers and make sure you’re getting a fair bid.

8. Building a Frankenstein system

Finally, let’s talk about the phone call our system designers dread:

“I have an inverter from eBay and some panels I bought a few years back, can you help me build the rest of my system?”

A fair number of people hold out for great deals and acquire parts slowly over time, until they’re ready to slap all the parts together like some kind of solar-powered Frankenstein’s monster.

But just like with cars or computers, it’s not enough to have parts. You have to have the right parts that are compatible with each other.

Otherwise, you get…

  • inverters that are undersized for your panel output
  • panels that are different sizes and don’t fit together properly on the mount
  • components that don’t wire together because they have different connectors
  • a power center missing essential components like circuit breakers/disconnects, remote control, or monitoring hardware
  • a box of hodgepodge components that no one is willing to support because it was purchased from all over the Internet
  • …and countless other headaches

There’s a lot that can go wrong, but the bottom line is piecemeal systems like these can quickly turn into a disaster. Unless you start with a plan and stick to it, there’s no guarantee the parts you buy will ever work together.

How to Avoid These Costly Solar Mistakes

You might notice that you can’t actually buy a complete system from our website cart. We require that people get in touch for a design consultation first.

Why do we do it this way? Even though we don’t install equipment, we’re still responsible for designing your system properly. If we sold systems with incompatible parts, we’d get a bad reputation in a hurry.

Instead, we run the math on system sizing, plan for inefficiencies, check voltage requirements, provide wiring diagrams, and do whatever else it takes to make sure the system you build is going to work.

For off-grid systems, we even assemble pre-wired power centers in our warehouse so you don’t have to worry about piecing the components together.

Our advice: do as much research as you can to account for all possible variables. But before you pull the trigger on that big investment, run that design by a solar designer first. An experienced set of eyes could help you catch some potentially costly mistakes before it’s too late.

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