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March 6, 2024

Solar Learning Centre

Cost of Microinverters vs. Cost of String Systems 

Comparison of the cost of micro inverters versus the cost of string inverters for solar power systems.

Are you shopping for a solar system? Probably, right? I mean, you found this article, so you must be at least interested. There’s a lot of information out there that you’ll need to sort through to figure out your specific needs.  

A big decision you’ll have to make early on is whether you want to install a microinverter solar system or a string inverter solar system. The inverter debate is always a heated topic of conversation when shopping for solar.  

There are advantages and disadvantages to each type of technology. However, the price of each type of system is generally what people look at when making this decision, and what we’re focusing on in this article. 

At Penrith Solar Centre, we install microinverter solar systems. We’re a little biased about what type of system we think you should install (for a variety of reasons), but we’re going to give you the honest truth about our product and our competitor’s product. And we’re going to do it exclusively from a cost/pricing point of view. 

In this article, you will learn: 

  • Microinverters vs. String Inverters: What’s the Difference in Upfront Cost? 
  • Do Microinverters or String Inverters Last Longer? 
  • What Costs More to Maintain: Microinverters or String Inverters? 

By the end of this article, you’ll understand why and how microinverters and string inverters are priced so differently from each other. 

If you’ve just opened this article, started reading, and are very confused about what a microinverter or string inverter is, you might want to jump back (for your own understanding) to a previously published article that lays out the differences between string inverter solar systems and microinverter solar systems titled, Microinverters vs. String Inverters: An Honest Comparison

Microinverters vs. String Inverters: What’s the Difference in Upfront Cost? 

When pricing a solar system, the math around calculating the cost is a little different from pricing anything else. There’s the upfront cost of installing the system, which is one price, but there’s also the price of your return on investment. That second price will fluctuate (sometimes greatly) depending on how much energy you use and what type of system you choose to install. 

Micros vs string inverters.

Upfront Cost of Microinverters: The cost of a microinverter solar system with Penrith Solar Centre is based on the size of the system you want.  

  • A 5 kW system costs about $2.00 per watt, totalling around $10,000.   
  • A 10 kW system costs about $1.30 per watt, totalling around $13,000.   
  • A 20 kW system costs about $1.30 per watt, totalling around $26,000.  

Because we are an in-house solar installation company, our installation fees are fixed at a day rate.  

Any solar system above 36 panels (approximately 16kW) will require a second day to install the system simply due to the size of it. There’s a price jump for installations that are larger than 36 panels, and it’s that second installation day that drives up the upfront cost.  

There’s a sweet spot in our pricing that’s a fantastic opportunity to save some money. A string system installed by subcontractors will be cheaper up to a certain point. But because a subcontractor charges by the panel rather than charging a fixed day rate, as the size of the system increases, so does the installation cost.  

Less than 8kW will most likely be cheaper with a string system, but when you go above 8kW, you get into some interesting math that most string solar sales companies can’t quite explain away. The string system will still be cheaper upfront but by a much narrower margin.  

If your solar system is bigger than 8kW, but will only take one day to install, you’ll be getting a favourable rate for your solar that installing a string system will have trouble undercutting. 

If you’re interested in learning more about the cost of microinverter solar systems, you might want to check out the following article titled, How Much Does a Microinverter Solar System Cost? 

Enphase Microinverter.

Upfront Cost of String Inverters: String inverter solar systems have a lower upfront cost. How much lower depends on which solar company you’re getting quotes from. Some solar sales companies are a little less expensive than us and some are considerably lower than us… upfront anyway. 

A string inverter solar system of any size will cost approximately $1.00 per watt, making it really easy to calculate the price. String inverter installers usually charge per panel to calculate the installation costs. 

  • A 5kW system costs about $1.00 per watt, totalling around $5,000. 
  • A 10kW system costs $1.00 per watt, totalling around $10,000.   
  • A 20 kW system costs about $1.00 per watt, totally around $20,000. 

As you can see, a 5kW string inverter system is about half the cost of a microinverter solar system of the same size, but as the size of the system increases, the cost of the installation increases.   

If you’re interested in learning more about the cost of string inverter solar systems, you might want to check out the following article titled, String Inverters: Are They Worth It?

A graph showing the return on investment for a 5 year investment.

Brief Note About Payback Period and Return on Investment: It is a challenge to estimate the payback period and return on investment for either solar system (the second price that fluctuates, which we mentioned above). There are so many variables that will affect this figure.  

  • What size is your solar system? 
  • What’s the cost of electricity per kWh from your energy retailer?  
  • Did you include a solar battery in your system? 
  • What are the feed-in rates with your DNSP or VPP?  

Calculating these figures is best done with the help of a solar consultant, and you should talk to consultants who install both microinverters and string inverter systems to get clear numbers that are useful to you.  

At Penrith Solar Centre, we take several things into consideration as we figure out what system will save you the most money over time. For a well-designed residential microinverter solar system, the minimum payback period is around 4-5 years. It might be longer if there are any unforeseen expenses in the installation process (additional days) or if you add-on any additional components (like a solar battery).  

A string inverter solar system may or may not have that short of a payback period. It depends on how well the system performs. We expect it to pay itself off in less time because it costs less to install, however, the efficiency and performance of string inverter systems leave much to be desired and will often extend this payback period (sometimes significantly).  

And remember, as you calculate the cost of electricity over time, the cost per kWh is rising quickly. In the past year, we experienced two large increases in the cost of electricity. If you’re not self-consuming most of the electricity your solar produces, it will be difficult to keep up with the rising cost of energy from your energy retailer due to inflation.  

If you’re interested in learning more about calculating the cost of a microinverter solar system, you might want to check out the following article titled, What is the Payback Period for Solar Panels in Australia? 

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Do Microinverters or String Inverters Last Longer? 

Like everything in life, you get what you pay for, and it will last longer the better you care for it. How long your system is expected to last will contribute greatly to the cost of your system over time. The longer it lasts, the better bang for your buck.  

Microinverter Lifespan: This is a very important factor to look at when you’re estimating long-term savings from your solar system.  

A microinverter solar system installed in Australia has a 15 year warranty on the microinverters. In the United States, they have a 25 year warranty, but that is unavailable in Australia because of stricter consumer protections.  

Microinverter warranty period.

String Inverter Lifespan: The warrantied lifespan for most string inverters is considerably shorter than the lifespan of a microinverter.  

While a string inverter solar system and a microinverter solar system will have similar variables, when it comes to calculating the payback period and return on investment, you must look at the protected and projected lifespan.  

A Fronius string inverter (the leading brand) will have a warranty of 5 years with an option to purchase an additional 5 years.  

A string inverter with warranty information.

Without adding the warranty extension for either microinverters or a string inverter, the string inverter is only certified by the manufacturer to last a third of the time a microinverter will (5 years vs 15 years). This means you will replace it two more times before you reach the lifespan of a microinverter.  

If you want your string inverter solar system to last as long as your microinverter solar system, well, I don’t know what to tell you. It just can’t.  

According to the manufacturer, you’ll need to replace it twice to get it to last as long as a microinverter.  

If you’re interested in learning more about warranties for solar equipment and installation services, you might want to check out the following article titled, A Complete Guide to Solar Warranties

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What Costs More to Maintain: Microinverters or String Inverters? 

Microinverter Maintenance Costs: At Penrith Solar Centre, we have a workmanship warranty for service on top of the manufacturer warranty that the microinverter manufacturer offers. If your microinverter solar system stops working or if you have equipment and components that need replacing, Penrith Solar Centre takes care of that for you.  

The ongoing maintenance cost is $0. It’s included in the cost of the system. 

A diagram of a string inverter system and a micro inverter system.

String Inverter Maintenance Costs: We mentioned the lifespan of a string inverter in the previous section, but the timeline for repairs and the cost of getting that inverter repaired varies, sometimes significantly.  

Let’s go on a journey together. Here’s a hypothetical situation to consider: a year or two after you installed a string inverter solar system, the inverter stops working.  

Did you even notice that your system stopped working?  

Time is expensive in the solar industry. If your system stops working, you’re spending money on expensive, grid electricity at over $0.32 per kilowatt hour while it’s offline.  

Microinverter solar systems offer consumption monitoring through an app on your phone. At the press of a button, you can know how your system is performing down each individual panel. Enphase microinverters come with this software for free. It’s helpful if anything goes wrong with your solar system. Of course, some string inverter solar systems also offer consumption monitoring, but because of how string systems work, you don’t get panel level monitoring without DC optimisers.

For a string inverter solar system without Dc optimisers, you’ll probably want to invest in also purchasing a third-party monitoring system because most string inverter monitoring apps are limited and can’t report on solar efficiency at the panel-level. Solar Analytics is a popular third-party option for many who invest in a string inverter system. It adds about $800 to your system and you’ll also have to subscribe to the software (which runs $5.99 per month).  

Okay, I know that was a bit of a walk to just let you know that you’ll want to spend an additional $800 on components and software for Solar Analytics to make it closer to the capabilities of Enphase microinverters, but that little investment could save you a lot of money and heartache down the road. 

Let’s say you only have the included string inverter system monitoring software and didn’t invest in third-party software because you wanted to save $800. Because of this cost-saving choice, you don’t know that your string inverter is busted.  

You get a quarterly energy bill. It’s a little high, but it’s summer and you’ve been running the air conditioning a lot, so you don’t really think about it. You don’t know that your solar system is broken. 

Then the next bill comes, and it’s enormous. You’ve gone an entire quarter (possibly more) without your solar system working. How big is your electricity bill? Is it over $1,000 per quarter?  

Subcontractor repair cycle graphic - Source: Penrith Solar Centre

Something’s not working. You call the company that sold you the solar system, but they only cover the sales component of the installation process. They tell you that you need to get ahold of the subcontractor they hired to install your string solar system.  

Let’s pretend the solar sales company has the contact information for you instead of cutting you loose and letting you track that electrician down on your own (which happens more often than you’d imagine).  

You call that subcontractor immediately, but they’re a little busy with other installations and can’t fit you in for another week at the earliest. And time is expensive in the solar industry. 

The subcontractor finds some time in their schedule and goes to your home to look at the system. As we mentioned above, a monitoring app helps diagnose issues with your solar system rapidly and efficiently. If you don’t have that tool, it’s going to be difficult to diagnose the issue.  

A $5,000 is now costing $6,000 because of that extra quarter of electricity bills. That’s a 20% increase of the original price. Every three months, the cost of your solar system jumps up another 20% of the original price.  

The subcontractor will probably figure out very quickly that the string inverter is the problem. He’s good at his job and knows it’s a mechanical failure. The panels and the equipment connecting everything to the inverter are all warrantied for 25 years or longer.  

The subcontractor reckons it’s the string inverter malfunctioning and directs you to take your claim up with the company that sold you the system. They are responsible for fulfilling warranties. 

But the sales company automatically questions if it’s the equipment. They want to verify that it wasn’t an installation error that the subcontractor they hired made instead. Investigating this takes time.  

The back and forth between the sales company and the subcontractor is eating up another quarter of electricity bills. You’ve spent another $1,000 on another quarterly bill. How much did that inexpensive string inverter system cost you in total? Now you need to add that $2,000 you just paid in electricity bills to your payback period.  

You’re starting to get really frustrated with the whole process and decide to file a fair-trade claim, but that takes time to process as well. And you’re going to see another quarterly electricity bill soon. How long does it take the government to resolve claims? If it takes a long time, you’re going to be paying for your energy again. 

Do you see what’s starting to happen with the cost of the system during the lifetime of the string inverter? Remember when we mentioned that the lifespan of the string inverter is a third of the lifespan of a microinverter?  

You still have to replace the string inverter two more times to match the lifespan of the microinverter solar system.  

And you might go through this cycle again if your next inverter stops working. 

The upfront cost for a string inverter solar system is lower. And it’s often significantly lower than the upfront cost of a microinverter solar system.  

You will pay more for a string inverter solar system over time. 

More on Micros!

Strings or Micros: Connecting the Watts 

Now you have a much better idea of what you need to be thinking when it comes to comparing the overall cost of a microinverter solar system to a string inverter solar system. The price will vary depending on the many factors you need to consider when installing a solar system.  

You’ll need to evaluate the upfront costs against the payback period for each type of system. As you collect quotes from string inverter solar systems, be certain to confirm the costs of installation and what type of warranties a solar installer fulfils.  

At Penrith Solar Centre, we believe in microinverters, but we believe in customer satisfaction above and beyond our private interests. Microinverters are a part of your solar system that costs more upfront but saves you money long term. A string inverter solar system will save you money upfront, but you risk quite a bit more money long term. The choice is entirely yours, we’re just here to make sure you make the right one for your needs. 

If you’re interested in learning more about microinverters, you might want to check out the following article titled, Myths & Misconceptions About Solar Microinverters

A group of people posing in front of a building at Penrith Solar Centre.

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