20 solar pow­er stor­age units from 15 man­u­fac­tur­ers were put under the micro­scope by the Berlin Uni­ver­si­ty of Applied Sci­ences (HTW Berlin) in the fourth edi­tion of the pow­er stor­age unit inspec­tion. In addi­tion to E3/DC, Growatt, Son­nen and Viess­mann, six oth­er man­u­fac­tur­ers par­tic­i­pat­ed in this year’s stor­age com­par­i­son for the first time or with new prod­ucts. The result: the pre­vi­ous effi­cien­cy record was beat­en by two elec­tric­i­ty stor­age systems.

Not only has the num­ber of pho­to­volta­ic bat­tery sys­tems installed in Ger­many increased sig­nif­i­cant­ly in recent years, but so has their ener­gy effi­cien­cy. This is the assess­ment of the research group Solar Stor­age Sys­tems of the HTW Berlin in the Elec­tric­i­ty Stor­age Inspec­tion 2021.

The 20 elec­tric­i­ty stor­age sys­tems eval­u­at­ed with the Sys­tem Per­for­mance Index (SPI) com­pet­ed against each oth­er in the 5 kilo­watt peak (kWp) and 10 kWp per­for­mance class­es. The high­est SPI (5 kWp) was achieved by the hybrid invert­er Fro­nius Pri­mo GEN24 6.0 Plus togeth­er with the BYD Bat­tery-Box Pre­mi­um HVS 7.7. In the larg­er pow­er class, the Pow­er Stor­age DC 10.0 device from RCT Pow­er came out on top with an SPI (10 kWp) of 95.1 per­cent, set­ting a new effi­cien­cy record. Fro­nius, Kaco and Kostal also scored with an excel­lent SPI (10 kWp). “Over­all, we were able to cer­ti­fy 13 elec­tric­i­ty stor­age sys­tems as hav­ing very good sys­tem effi­cien­cy,” sums up Prof. Dr. Volk­er Quaschn­ing, Pro­fes­sor of Renew­able Ener­gy Sys­tems at HTW Berlin and co-author of the study.

The researchers explain the fre­quent­ly improved invert­er effi­cien­cies among oth­er things with the increased use of sil­i­con car­bide pow­er semi­con­duc­tors. As a result, the most effi­cient sys­tems achieve effi­cien­cies above 97 per­cent over a wide pow­er range. Fur­ther­more, there is a trend towards hybrid invert­ers, which com­bine all pow­er elec­tron­ic com­po­nents in one device. Over­all, the Elec­tric­i­ty Stor­age Inspec­tion 2021 high­lights six tech­nol­o­gy trends in the bat­tery stor­age market.

In a fur­ther focus of the study, the authors inves­ti­gate fre­quent­ly asked ques­tions about the design of pho­to­volta­ic stor­age sys­tems. In par­tic­u­lar, they advise own­ers of homes with a heat pump or an elec­tric car to install as large a pho­to­volta­ic sys­tem as pos­si­ble with an out­put of at least 10 kWp. After all, a 10-kWp pho­to­volta­ic sys­tem occu­py­ing about 50 to 60 square meters of the house roof can avoid four to five tons of CO2 annu­al­ly. “The more solar pow­er pro­duced on the roof, the greater your own con­tri­bu­tion to cli­mate pro­tec­tion,” adds Prof. Quaschn­ing. Against this back­ground, all suit­able roof sur­faces should be used for the pro­duc­tion of solar electricity.

The elec­tric­i­ty stor­age inspec­tion will be con­tin­ued over the next three years in the “Per­form” project fund­ed by the Fed­er­al Min­istry for Eco­nom­ic Affairs and Ener­gy (BMWi). Stor­age man­u­fac­tur­ers can par­tic­i­pate in the next edi­tion of the stor­age com­par­i­son until the end of 2021.

Down­load the study Elec­tric­i­ty Stor­age Inspec­tion 2021