• Solar Inverters including Micro Inverters
• Solar Inverters
• On-Grid Inverter also called Grid-Tie Inverter
• Stand Alone Off-Grid Inverters
• Hybrid Inverter Setups
• Micro Inverters vs Conventional Inverters
• Advantages of Micro Inverters
• Enphase Micro Inverter
• Conventional Inverter Cost
• Inverters In Summary
• Micro Inverter Benefits
• Advantages of Conventional Inverter

Solar Inverters including Micro Inverters

“Inverters” — what are they? Why do you need one? Is it something you can build yourself? What are the different types of inverters that could be used on a solar panel installation? What is a micro inverter and how does that compare to a traditional inverter? Which is the best to use for your homemade solar panel project? This article will attempt to clarify all these issues for you.

All kidding aside with the rock band AC/DC — when you build a solar panel, you have to convert the energy it produces into energy you can use. Solar panels produce “direct current” (DC). Before you can use the power in your home, it must become “alternating current” (AC). A conventional inverter takes the DC input from many sources (lets say — 3 solar panels and 1 wind turbine) and converts it to electricity you can use in your home. A micro inverter will convert the DC to AC right at the solar panel, before it hits the power line attached to your house. Before we discuss the differences between micro and conventional, following is a discussion of different types of solar inverters.

Solar Inverters

I wanted to make this article all-inclusive in regards to solar inverters, because you could have different goals for an inverter that both micro and conventional would fulfill. There are several paths you could take when finding an inverter for your solar panel installation. Below I discuss the different systems.

On-Grid Inverter also called Grid-Tie Inverter

Below is an image representing the concept of a grid-tied inverter. You will notice that your solar power can either switch to your internal home and used to power appliances, or switch to feeding the power lines of your local electric company.

This type of solar panel installation is the “net metering” setup. Net metering is where the excess power you generate is funneled to the electric company, and they pay you for it. Typically, during your 4 to 6 hours of solar “peak time” during the day, you feed a huge surplus of energy to your local power grid. Then, as the evening hours and night time approach, your power usage will continue even though the sun isn’t shining. In effect, your local power company becomes your “battery”, you supply them extra power during your surplus hours of peak sunshine which you extract at other times. It is possible to have such a large surplus that it entirely offsets what you use during the evening, which is the point your home breaks even on electrical usage for a $0 electric bill. In most areas (over 39 US states) currently have agreements to issue payments to you if your supply to the local power grid exceeds your own home usage of electricity.

Stand Alone Off-Grid Inverters

I absolutely loved “The Colony”, a TV show by the Discovery Channel. The premise of the show is surviving after a global bacterial disaster that shakes the fabric of society. How would one survive during this calamity? One of the cast was Michael Raines, a fabricator and solar panel installer.

In one episode, the colonists found an inverter. They scavenged 12 car batteries and daisy-chained them together into one large battery unit. To be able to use the energy from the batteries (which is DC) they used the inverter to convert to AC, which allowed them to power electric lights at night, and run their power tools. This gave them a week of power usage until they built a wood gasifier generator to recharge the batteries. In a later episode, Michael Raines scavenged solar panels from a nearby roof and took the DC power it generated straight to the DC power battery array, not converting to AC power with the inverter until the time of electrical use.
With a stand-alone off-grid system, you are not using the local electrical company to offload your excess power generated during peak hours of sunshine — instead you are storing them in batteries.

The benefits of this system are obvious. Electrical power is not available everywhere. If you have a small cabin in the woods, or do not have access to the main power grid where your home is located at — an off-grid solar panel system can be a lifesaver. Even if you have access to the power grid, your specific area may not be set up for “net metering”, so you would have no desire to give the electric company power for free.

Hybrid Inverter Setups

There are various setups you can use with solar inverters that include both net-metering and battery storage, the above was just to give examples of the most popular setups — using the power grid as storage, and using batteries as storage.

Micro Inverters vs Conventional Inverters

Now that we have established what an inverter is and how they are used in typical solar panel installations, lets address micro inverters compared to conventional inverters. A conventional inverter involves one location where all power units feed in to be converted from DC to AC. Micro inverters, on the other hand, reside at the solar panel itself. A micro inverter services one, or a few solar panels (enough to max its capacity), converting DC into AC before it is fed into the power line.

Advantages of Micro Inverters

Micro inverters have a strong following in the solar panel community. AC power runs through electric cords more efficiently than DC. In fact, many people claim excess power production of as much as 25% by using micro inverters. Furthermore, micro inverters are individually less expensive than a conventional inverter. If a conventional inverter fails, it will be expensive to replace. Micro inverters, should they fail, are far less expensive to replace. In addition, many claim that micro inverters are far less likely to fail because of the smaller amount of electricity they must process when compared to a conventional inverter.

Another major benefit of micro inverters is scalability. Lets say you eventually want to build a 4 kWh solar panel installation for your home, but you want to start out slowly. A 4 kWh conventional inverter is going to be expensive, well over two thousand dollars. If you want to start with a simple 120 or 240 watt solar panel, it makes far more sense to set it up with its own micro inverter. Then as you add new solar panels, each time add a new micro inverter. You never have to worry about producing too little, or too much, for a large conventional inverter when you use micro inverters.

Enphase Micro Inverter

How much does a micro inverter cost? Enphase is one of the better micro inverters available today. They cost around $190 US as of Fall of 2010. This functions as a grid-tie inverter — this will allow you to add just one solar panel to your house and immediately begin seeing a difference in your electric bill (and immediately begin making money with your electric company with net-metering, assuming you are not using the power for your household). The Enphase micro converter boasts a 25% power boost to your solar panels. Because AC travels through wires more efficiently than DC power, inverting DC to AC right at the solar panel with an Enphase micro inverter will give you more power from your solar panels. The following video gives more information about the Enphase micro inverter.

Conventional Inverter Cost

Whereas micro inverters are costing approximately $1 per watt (as referenced above — the Enphase micro converter runs approximately $190 for a 190 watt inverter), conventional inverters are less expensive. Typically, a conventional solar panel inverter will cost approximately 60 cents per watt.

Inverters In Summary

Following is a summary of the benefits you can expect to receive using a micro inverter or a conventional inverter.

Micro Inverter Benefits

• 25% boost to output of solar panel. AC travels through power lines more efficiently than DC, thus boosting the power generated by your homemade solar panel.
• Smaller “weakest link”. It is generally recognized that the inverter has a greater chance of failure than other parts of your solar system.  Using micro inverters reduces the chance your inverter will fail by processing lower volumes of electricity per unit, and if a single unit fails it will be cheaper to fix than an entire conventional inverter.
• Scalability. It is easier to scale your system using micro inverters, adding new solar panels and its corresponding micro inverter as you go — instead of having to purchase one large inverter to begin adding even a single solar panel.

Advantages of Conventional Inverter

Less expensive.  Of course, prices can vary depending where you shop — but for the most part, as of Fall 2010 micro inverters should cost around $1 per watt, whereas a conventional inverter will cost more around 60 cents per watt.

Conclusion

It is true, you can build a solar panel all by yourself, for less than $1 per watt.  Using those watts to run appliances, however, requires an alternating current.  Hooking an inverter up will increase the price to above $1 per watt — in fact, using a micro inverter is going to make hooking your solar panel up to your house more expensive than the solar panel itself.

Even so — solar panels are cheap to make today.  In reality, whether you build panels yourself or buy them professionally made, you cannot escape the need to invert the power — professional solar installers will charge you extra for an inverter (they are not included with the price of the solar panels).

Interested in more detailed information on how to, step-by-step, build your own solar panel?  Our detailed guide covers everything you need to know — from setting up your inverter, to actually building the solar panels themselves.  This article was very general in certain areas, however our guide is very specific.  It has hours of video, color diagrams, instructions on how to buy cheap solar cells off ebay and other information you need to make a solar panel.  Click below for more information.