Building Blocks of Solar Part 7 – Solar Inverters and Balance of system

Today we are going to discuss Inverters and the balance of system components.   Inverters are the component that takes the DC(Direct Current) Provided by the solar array and stored in the battery bank, and converts it to AC(Alternating Current) for your home use.  Alternating current means that the current alternates its direction over and over again(every 8 milliseconds) to create a nice wave pattern.  It goes up, rounds off, goes down, rounds off, and repeats.  

You want to match your inverter to your battery bank, so if you have a 24V battery bank you don’t want to buy a 12v solar inverter.  Once you have cut out or reduced usage of all the devices that you can, you need to do an analysis of the devices you still have and how often they are used to understand what the demands of your inverter are going to be.  You need to look at both the peak or startup loads as well as the running loads.  For example a refrigerator compressor may draw 5 times its running amps for half a second while starting up.  There are many tools on the internet that can help you with this as well, my favorite is over at the Alt-E Store.  Once you have your total Watt-Hours per day and your peak loads you can decide on an inverter.  

Here are a few things you need to consider while evaluating solar inverter choices.  

  1. Pure Sine Wave vs. Modified Sine Wave – these are the two main classes of solar inverters you will be looking at.  Sine waves are that nice up and down curve I spoke about before with rounded peaks and valleys.  Pure or True Sine wave Inverters create AC electricity that is just like the grid power.  Everything in your house was designed to run on true sine wave.  But that doesnt mean that it can run on Modified Sine Wave.  MSW is more blocky than TSW.  MSW goes up to peak for a few milliseconds, goes to zero for a few milliseconds, and goes down for a fe milliseconds and then repeats.  High tech and sensitive electronics may have problems with Modified Sine Wave.  Personally, with the price difference not being that much anymore, I would go with the TSW to ensure that I wasnt going to have problems.  ANother option would be to have a MSW inverter for normal loads and a seperate smaller TSW inverter for finisky loads.
  2. Inverter/Charger or not – An inverter/charger is a combination of an inverter, battery charger and transfer switch into one device. When a generator is on an hooked up, or you are hooked to the grid, the inverter recharges the battery bank. It also allows any surplus AC power to pass through and power houseAC loads, such as a television. When AC power is disconnected, the unit inverts DC battery power into AC electricity.  I would advise using this because it makes adding a generator to the system plug and play.
  3.  Future expand-ability – Some solar inverters play well with others and can be wired in parallel to expand the system and others cant.  If you are building out your system slowly this may be a consideration you should make.


Balance of System – The balance of system is simply the other components you need to complete your system.  These include wiring and combining the solar panels, fuses, safety switches, battery cables, disconnects, monitors and controllers or data displays, and mounting systems.

3 Replies to “Building Blocks of Solar Part 7 – Solar Inverters and Balance of system”

    1. Thanks, if there is anything you would like to hear about specifically let me know and Ill include it in a future podcast.

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