Bookmark and Share

Solar System Inverter Efficiency Tutorial on Curve,Types (CEC,European,Average)and Comparision – PV Efficiency Increasing Every Year

2 Comment

Solar Inverter Efficiency is increasing every year with increasing scale of operations,greater competition and rising R&D dollars being poured into solar inverter development.PV inverter Efficiency is vital to decrease the costs of solar power which is currently more than that of fossil fuels.While the cost of solar panels has come down drastically by almost 75% in the last 3 years,solar inverter costs have gone down by only 10% every year at most.The reason is that competition is lower in the PV inverter market because of the higher entry barriers of technology.While Western solar inverter manufacturers routinely get above 95% efficiency,the Asian low cost players have not been able to cross the technology hurdle of high efficiency.Note the Power Electronics in a solar system can make a huge difference to the power yields with even a 1% change resulting in thousands of dollars in difference in large scale solar farms.This is the reason that high efficiency 3 phase solar inverters from the West command a big price premium over the less reliable lower quality PV inverters.You should be careful of any lesser known inverter brand they are offered as part of a home solar power system before installing them. While some of these inverters may have certification this does not mean they can perform as well as the good brands.Skimping of a few dollars here and there may make you penny wise and pound foolish.

What is Solar Inverter Efficiency

Peak Efficiency of Solar Inverters -Inverters produce different power  at different voltages which means they have different efficiencies associated with each voltage.Inverter’s efficiency will increase sharply with the rise in voltage until it reaches it’s peak efficiency point. It will then remain close to level, decreasing slightly as the voltage increases..The peak efficiency represents the maximum efficiency that the PV inverter can perform at. Inverters these days even the worst ones have efficiency of at least 92-93% while the best ones in the market from SMA Solar in demo such as Sunny Towers can reach 99% using transformerless design.Note the Peak Efficiency is not very useful as it  is generally at around 20-30 percent of it’s Power Rating.Average Efficiency is a better measure.

Average or CEC weighted efficiency: n order to compare inverter efficiencies that are closer to real world operating conditions, several bodies have developed weighted efficiencies that factor electrical efficiencies measured at different levels of irradiation.The Average Efficiency is an average efficiency of the inverter performance and gives a better idea tha nthe peak efficiency.This figure is published by the California Energy Commission .CEC efficiency is calculated as an average value of DC/AC conversion efficiency at six pre-defined outputs between 5 % and 100 % nominal power

European Average Weighted Solar Inverter Efficiency – Euro efficiency is a weighted avaerage at a single input voltage.  The weigting factors are slightly different as well from the CEC. Note the main difference is that the weigthings at different power ratings are different.CEC gives higher weightage at higher power ratings while European gives lower weightage.

What is Solar Inverter Efficiency Curve

Solar Inverter Efficiency Curve is nothing but a plot of different solar inverter efficiencies at different voltages.A flat efficiency characteristic is usually desirable.Note MPTT systems in solar inverter systems these days try to optimize the power by applying loads such that the product of the current and voltage that is power is maximized.A key advantage of MPTT solutions is their capability to raise energy yields quite a lot without increasing the cost too much.Depending on the installation MPTT can boost the energy yields  by 5-15 percent.  Note the peak efficiency is the highest efficiency that you can get from the pv inverter in all the possible voltages that the inverter works at.It represents the highest point in the vertical axis of the solar inverter efficiency graph.

Comparision of Solar Inverter Efficiencies

Note comparing solar inverter efficiencies in isolation does not make a lot of sense since you should see all the features of a solar inverter such as price,down times,warranty,reliability etcI.nitial acquisition costs are important, but the lifetime costs of inverters are more important  thus quality and reliability are key buying features in the pv inverter market.However like solar panels ,inverter efficiency is one of the major decision points while buying a pv inverter.While there are litterally hundreds of inverters in the market with different efficiencies there is a general rule that you can follow in choosing manufacturers .

Western manufacturers in particular SMA Solar have much higher efficiencies than Asian ones.German made solar inverters from Kaco,Fronius,SMA Solar have the best efficiency.Then there are US based solar inverter makers like Power-One,Satcon that have equally good solar efficiency and are lower cost to boot.Asian makers from China like Sungrow and Kinglong have lower efficiency than everyone else but their costs are almost 40-50% lower as well.

Highest Efficiency Solar Inverters

 SMA Solar –TSMA Solar sells solar inverters which are of high efficiency and quality with most of its solar inverters giving 95% efficiency which makes it the leader in the market.SMA Solar has even started demonstrating transform-less solar inverters with 99% efficiency which is the highest efficiency solar inverter in the market

 Kaco New Energy – Like SMA,this is also a German company though privately held.It too benefited from the strong growth in German solar market in 2009 and 2010 to become a large players.It is has not grown as fast as SMA but is still a big players

 Fronius International – Very similar to Kaco in terms of its growth and being German.Fronius was a top 3 player in 2009 but has seen upstarts  like Power-One take more marketshare

 Schnieder Electric – This European Electrical Equipment Giant got into the solar inverter market by buying up Canadian Producer Xantrex.

Medium Efficiency Solar Inverters

Power-One – The US power management company has shown the fastest growth in 2010 and has increased its marketshare to around 13% to become the No.2 global player.Power-One is mainly concentrated in Europe and is now expanding to Asia and its home market of USA.

Satcon – Satcon is similar to Power-One but has not grown as fast nor does it have the high margins of its bigger competitor.It is strong in the US utility market and is growing its operations there.Like Power-One shifting its manufacturing

Lower Efficiency Solar Inverters

Sungrow products has most of the international  Certificates such as TUV, Enel-GUIDA, AS4777, ETL, CE.Sungrow has more than 10 years working experience in research, development, production and sales of PV grid-connected inverters and it has launched a series of power plant inverters specially-made for medium & large scale of PV power plants  which rated at 100kW, 250kW, 500kW and 1MW

Kinglong -The company’s main selling point is its price which is cheaper than the European solar inverters.However you don’t get the efficiency of the premium models with Kinglong.The company sells solar inverters in the price range of $500 for a 1.5 kw inverter to $1500 for a 5 kw inverter under the brand of SunTeams.


Abhishek Shah

2 Responses so far | Have Your Say!

  1. David Dempsey

    Unfortunately, having cheap supposedly high efficiency and high reliability inverters such as Kinglong die after a year in domestic service means that they never achieve their claimed efficiency. This is very disappointing when the company then runs away from warranty problems! As their reliability is suspect, I now wonder if their efficiency is all that good.

  2. Hariharan K

    Hello Sir,

    Do you have any idea as to how the predefined power levels for the CEC and Euro efficiencies and the corresponding weights were determined?