The Solar Power Expert Blog

Grid-Tied Inverters

by Chris - February 7th, 2011.
Filed under: Equipment. Tagged as: , .

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Grid tied inverters are an element of alternative energy technology which is getting a lot of attention these days. Just a few years ago, these devices were very hard to find and very expensive to purchase. Today, new micro-inverters are being developed which cost between $200 and $300.

Grid-tied-inverters are an amazing technology for several reasons. First of all, a grid tied inverter is necessary in order to upload the energy from your DIY solar panels or wind turbines for the home to the grid and get paid for it. The second big reason is that these new devices do not require a significant battery pack in order to function.

Only a couple years ago, a typical solar system would require a large bank of batteries to store the energy. This represented a huge investment for the home owner before they could build a functional alternative energy system. Worse, batteries degrade with usage which means their expensive investment would literally decompose like rotting fruit as they used them. By removing the need for an expensive battery pack and replacing the large, expensive grid-tied inverters with smaller, cheaper units that don’t need batteries, it brings the implementation of a solar or wind powered home within the financial grasp of many more people.

If you are interested in the new possibilities that grid-tied inverters create, there is one red flag you need to be worried about. Many new, inexpensive grid-tied inverters are flooding the market – mostly from China. Most of these do not have UL certification (CSA certification in Canada), which is required before plugging it into the power grid. Even if the unit works fine, it is technically a federal crime to plug these units into power grid. Even if you get a great deal on a non-certified grid-tied inverter and it causes damage to the grid, you will be held personally liable for it. Additionally, you may have your power cut off permanently and be fined or imprisoned. So before purchasing a grid-tied inverter, be sure to verify that the unit is UL certified.

The final advantage of grid tie inverters is that they are scalable. If you add more solar panels or wind turbines to your home, you can simply add an additional grid-tie inverter in parallel with your existing one to scale up your power handling capability.

2 Responses to Grid-Tied Inverters

  1. How do I know what size of inverter or how many inverters I need? For example, if i have a 550W grid tie inverter and I have five 150W solar panels, would I need a second inverter for the fourth and fifth panels?

  2. Hey Jason,

    That’s a really good question. Unfortunately, there is no cut and dry answer. However, keep in mind that the power ratings for both your inverter and the solar panel are maximum power ratings. Your solar panel will rarely achieve its maximum rating (except under full, direct sunlight).

    Personally, if I was you, I would incorporate a small battery bank and charge controller and arrange them in a way so that any power above what the grid tie inverter can handle will be routed to a battery. This excess energy can then be fed into the inverter at a later time when the panels aren’t putting out so much power. This would be a complicated and technical implementation however.

    A simpler answer would be just to make sure the combined power rating of your inverter is higher than the combined power of your solar panels.

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