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How to Choose an Inverter-Charger

By Kris de Leon June 15, 2017


Off-grid solar systems mean just that. They are designed to run in isolated areas and function completely independent of the utility grid. Off-grid solar systems have several additional components necessary for the system to work. Solar power can only be produced during the day and when there is sun.

With an off-grid system the DC power collected by your solar panels is sent to a device called a charge controller. The charge controller takes the incoming power from the panels and sends it to a battery or bank of batteries in which the electricity is stored. The charge controller is responsible for filling the batteries when they are low or stopping the electricity from the panels from reaching the batteries when they are full. The stored DC electricity in your batteries is then sent to an inverter, converted to AC electricity and sent throughout your property for use when you need it.

Off-grid systems are a lot more expensive than grid-tied systems due to the added cost of batteries, one or more charge controller as well as other protective devices and cabling. Typically an off-grid system is also designed with a slightly larger solar panel array than a standard grid-tied system to make sure you have enough power for your daily use and to keep your batteries full and prepare you for days without sun.

There are many benefits to having an off-grid system. Besides having power where there is otherwise no other available option (remote locations without access to the grid) the most attractive aspect of off-grid living is being 100% independent of utility electricity. You are harnessing, storing and using all of your electrical needs. Moreover, with a properly designed system, you won’t be running out of power for several years before you need to consider replacing your battery bank.

The next question is, what do you do if your power needs fluctuate or your loads exceed your solar panels capacity to produce enough power? The solution – a hybrid solar system with an inverter-charger.

Hybrid Solar Systems

The main distinguishing feature of a hybrid system is that it uses both DC electricity stored in your battery bank and AC electricity from the grid or from a generator to make one seamless system. Hybrid solar systems take the luxury of having energy stored in batteries and make it available for your use when the grid-is down, during storms, natural disasters as well as any other situation in which you may lose electricity from the utility company or not have enough sun (solar power) to run your loads for an extended period of time.

The design of a hybrid system essentially makes your standard off-grid system limitless in the power it can provide. With a hybrid system your inverter uses electricity from your batteries (which charge from the charge controller and ultimately the panels and sun) and power from the utility company and/or a generator.

Inverter Charger Off Grid

In a typical off-grid solar system you are limited by the power stored in your batteries and the maximum possible output of your inverter. In the above off-grid photo you can see there is a 3000 watt inverter being used. This means at any given time the customer cannot use more than 3000 watts.

With a hybrid system you are only limited by the inverters rated output when you are using power stored in the batteries. This is because your inverter does not have to convert the connected grid AC electricity; it simply needs to pass it through to the loads in your house.

This type of system has become a lot more common in recent solar history due to the luxurious aspect of having electricity all of the time (even when the grid is down), taking advantage of tiered pricing from the utility company (only using grid electric when the rate is at its lowest during the day) and for the protective role it plays to prolong the life of appliances and electronics in your home.

As previously discussed, a strictly grid-tied inverter shuts off when the grid goes down or the grid input is above or below an acceptable voltage. These spikes and drops in incoming grid voltage can be detrimental to the lifespan of your electrical components; especially sensitive electronics and products with motors and compressors.

With a hybrid system, when the AC input to the inverter is above or below a certain threshold the inverter will switch to back-up battery mode automatically to provide the purest and most stable electricity possible.

For restaurants, hotels and other service-based businesses in remote areas, the peace of mind associated with energy back-up and device over and under-voltage protection can be a nearly priceless commodity. This holds especially true for hospitals and nursing homes where an electrical outage can create worse problems than a failing refrigerator compressor or a freezer of bad food after a day without power.

The benefits of hybrid systems are most significantly acknowledged in the overall cost of the system. For this added luxury there is undoubtedly a significant price to pay.

What to Consider When Choosing an Inverter-Charger

There are several things to consider when choosing an inverter-charger for your hybrid solar system. The first is the form of electrical output. In the most basic of ways there are two types of electrical output; modified sinewave and pure sinewave. In nearly every case you will want a pure sinewave inverter. This form of electrical output is the same as you will find coming from the utility grid. The benefit of a pure sinewave inverter is that the output is always consistent, rather than the fluctuations you may encounter coming from your local utility grid.

The second consideration is to make sure you size your inverter-charger to match that of your loads. If you have 3,000 watts of continuous electric need on your property you are going to want an inverter-charger that can handle these loads with ease. Prepare to invest in an inverter-charger that can handle at least 1.5 times the load that you have. In the case of a 3,000 watt continuous demand on your property you will want at least a 4,500 watt inverter-charger.

Your battery bank should also be sized accordingly in relation to your load, solar production and the amount of time (in days) that you would like storage without input from the sun and solar panels. The beauty of a hybrid system with an inverter-charger is if you should have several days without sun and your batteries are draining below a healthy depth of discharge, your inverter-charger will take electricity from either the utility grid or a generator to maintain the battery voltage, keep your batteries at a safe voltage to avoid damage and provide you with continuous, uninterrupted power.

Outback Inverter Charger

One of the biggest advantages to an inverter-charger is the common ability, with certain models, to also sell electricity back to the grid. With an inverter-charger you can not only have uninterrupted power but also harness your extra power and sell it back to the grid. The connection works both ways, again, with certain models (such as the Outback Power FXR series). You can both charge your batteries from the grid and sell excess power back to the grid when you are not using the power produced by your solar panels.

As always with all of our articles here on SolarTech Direct the top consideration should be quality. When shopping for an inverter-charger you are looking for a system that will seamlessly and flawlessly provide you with power. This is the heart of your solar system and a cheap approach to purchase is one you will likely regret down the road. Consider using some of the best inverter-chargers in the World such as Outback Power, Magnum or Schneider Electric. All three are top tier companies with decades in the industry. Their products have not only proven durable and reliable in the field but their warranties are there to back them up.

Outback Power provides U.S. manufactured and designed inverter-chargers that are considered the best of the best in the solar industry. Their impeccable and free customer support a well as a standard 5-year warranty also helps to make the decision to go with Outback Power an easy one.

Now that you understand the difference between a strictly off-grid system and a hybrid system with an inverter-charger, please continue reading to find out how to choose your other solar components and which type of system is best for your particular use.

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