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Inverters serve a very important function when it comes to generating your own electricity using solar panels. Solar panels produce direct current (DC) like batteries, but most of your home appliances require alternating current (AC) to run.
A solar inverter converts DC power into AC power so your electrical equipment can use the kilowatt hours produced by your solar panels.
However, solar inverters have another important function that is less known – they synchronize with the voltage and frequency of the local grid.
In this way, homes and buildings can switch between solar and grid at any time, or they can use both energy sources at the same time – all without the use of physical switches.
Traditional string inverters are designed to convert only DC power from solar panels, but many systems now include batteries.
If you plan to use energy storage batteries in your home solar system, you will need a hybrid inverter.
Hybrid inverters are designed to manage solar panels and batteries working together.
Below we’ll discuss the main features you should look for in a solar inverter, and we’ll also compare the main types available on the market today.
Choose a high-quality solar inverter
If you want to get the best results from your solar energy, the quality of your inverter is just as important as the quality of your solar panels.
Remember, all the electricity generated passes through the inverter before it can be used by your home appliances. You can use the most efficient solar panels on the market, but if your inverter is of poor quality, overall system performance will be poor.
When comparing different solar inverter models, you should look for the following specifications as a starting point:
Conversion efficiency from DC to AC power
Solar inverters from leading manufacturers have typical conversion efficiencies of over 97%.
In other words, for every 100 kWh produced by solar panels (DC), they provide more than 97 kWh of usable electricity (AC).
The table below compares several popular 5 kW inverters for home solar systems:
Brand Product Conversion Efficiency
SolarEdge HD-Wave(5 kW) 99.2%
Huawei SUN2000(5 kW) 98.4%
Sungrow SG Series(5 kW) 98.4%
SMA Sunny Boy(5 kW) 97.6%
Fronius Primo GEN24 Plus (5 kW) 97.6%
High-quality solar inverters have a typical lifespan and usually include a standard 5-year warranty. However, depending on the specific inverter you choose, the manufacturer offers an extended warranty of 10 years or more.
Pro tip: It’s important to have a solid warranty: If your inverter fails during the warranty period, you can get a new one for free. Always contact a qualified solar installer to ensure your solar panel and inverter warranty is not voided due to incorrect installation!
A high-efficiency inverter with a long warranty ensures stable power from your solar panels. However, you must also consider other important features when comparing inverters.
There is a common misconception that your solar inverter capacity should match the total wattage of your solar panels, but this is not the case.
The capacity of an inverter is lower than its corresponding solar array.
You can only determine the optimal inverter capacity through professional solar design.
However, solar systems typically have a DC-AC ratio of 1.25 or higher.
For example, if you connect a 6kW solar panel system (DC) to a 5kW inverter (AC), the DC-AC ratio is 1.20.
This value is also known as the inverter load ratio or ILR.
There are technical reasons for using an inverter capacity lower than the wattage of the PV array.
Considering that solar panels are tested under ideal laboratory conditions, this does not represent actual conditions for rooftop installations.
Therefore, the solar panel only produces nameplate wattage for a small fraction of its operating time.
If you install an inverter that matches the total power of your solar panels, it will operate at less than its rated capacity in most cases.
In other words, you are paying for extra inverter capacity that is almost never used.
You can get a better return on investment and “cut” the occasional residual solar peak with a smaller, cheaper inverter.
The best solar inverters have a feature called MPPT, which stands for Maximum Power Point Tracking. MPPT is a power optimization method,
Increases the power output of solar systems – when they are more productive, the savings on your energy bills are also higher. MPPT technology is based on the following principles:
Sunlight conditions are constantly changing, and depending on the time and season, the ideal operating voltage and current of a solar panel will also change.
An MPPT circuit continuously adjusts the voltage and current of the photovoltaic array so the solar panels can provide more power.
Sunlight conditions also vary depending on the orientation of the solar panels. For example, east-facing panels get more sunlight in the morning, while west-facing panels get more sunlight in the afternoon.
When solar panels with different orientations and sunlight conditions are connected to the same circuit, it can negatively affect their efficiency.
However, some solar inverters have two or more MPPT circuits – solar panels can be grouped and connected together based on their orientation, so the entire system becomes more efficient.
As mentioned above, traditional inverters are designed only for solar panels, while hybrid inverters can also control battery systems.
The ideal inverter choice for your home solar system depends on your plans:
If you only want to install solar panels and have no plans to add batteries in the future, it is recommended that you use a traditional string inverter.
If you want a home solar system with energy storage, you must use a hybrid inverter.
Solar cells are still expensive, and their payback period can vary depending on local incentives and electricity prices.
If your electricity supplier offers net metering on favorable terms, you can use the local grid as your “battery” – surplus power from your solar panels is sent to the grid around midday and deducted from your consumption after sunset .
However, not all electricity suppliers have favorable net metering conditions. Some of these only provide partial credit for the remaining power generated by the solar panels – for example, you might pay 16 cents/kWh but only 8 cents/kWh when exporting solar power.
There are also electricity suppliers that do not offer net metering, and all kilowatt hours sent to the grid are lost and no credit is given.
When net metering is not available or feed-in tariffs are very low, it makes sense to combine solar panels with batteries.
In this case, you need a hybrid inverter to manage the energy flow from both the solar panels and the battery.
Here are some other scenarios where batteries can provide an attractive ROI:
When your electricity supplier charges time-of-use rates, they are usually higher at night. With batteries, you can store electricity from your solar panels and use it during peak demand hours—eliminating the most expensive kilowatt-hours from your electricity bill.
When your electricity provider has a demand response or virtual power plant program. In these cases, the utility will encourage solar cell owners to join their program. For example, you might be rewarded for supplying power to the grid during peak demand times.
If you only plan to install solar panels but consider energy storage in the future, a hybrid inverter is recommended. If a traditional inverter is installed, it will be forced to be replaced when energy storage is added.
However, a hybrid inverter can function properly using only solar panels, and batteries can be simply connected and configured in the future.
Maximum Power Point Tracking (MPPT) technology can be used in both conventional and hybrid inverters to increase their power output. However, MPPT optimizes the power output of the entire solar panel, and there may be situations where you need to optimize the solar panels individually. Here are some examples:
Some roofs may have complex designs with varying heights, orientations and pitch angles. In these cases, it may not be possible to group solar panels to have similar sunlight conditions.
Some roofs are suitable for solar panels, but they may present shading issues at certain times of the day or year.
In this case, optimal solar panel layout may not be achieved due to shading. Solar panels are connected in a string circuit, and a single shaded panel affects all other panels in the circuit.
Power optimizers and microinverters accomplish the same function—control each solar panel individually to maximize total power output. However, each device accomplishes this function in very different ways.
The power optimizer is comparable to MPPT circuits. They are small devices attached to each solar panel that optimize voltage and current based on sunlight conditions.
Power optimizers increase the DC output of your solar panels, but they don’t convert it to AC – you’ll still need a solar inverter for this purpose.
Huawei and SolarEdge are two leading inverter brands that offer power optimizers compatible with their products.
There are hybrid inverters that are compatible with power optimizers. In this case, you can increase the output of the solar panels individually while adding energy storage to the entire array.
Microinverters can also optimize the power output of solar panels while converting it into alternating current. Thanks to this feature, you will not need a separate solar inverter.
However, microinverters are not directly compatible with battery systems because the power is already converted to AC and the batteries are charged using DC voltage.
In this case, you will need a separate inverter just for the battery system, making the project more expensive.
As you might expect, both power optimizers and microinverters add to the cost of a solar system since each panel is equipped with a power conversion device.
For example, an array of 30 solar panels will require 30 power optimizers or microinverters.
These technologies are recommended only when solar panels cannot be grouped optimally and their additional cost can be compensated by increased power generation.
Written by: WTech
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