As an SMA employee, I was able to familiarize myself with the new Sunny Boy Smart Energy in the test phase. Many of you are probably wondering why you should invest in an inverter with a battery, so I would like to share my experience and take you through a few questions that could help you make a decision.
My current system is a Sunny Boy 3600SE-10 with a 2-kWh battery without Sunny Home Manager via WebConnect. My solar power output is 4.75 kWp. I receive 17.9 cents for each kWh I feed in. I have been running a battery inverter in my system for the last two months. Here are my experiences:
The Sunny Boy Smart Energy is really very simple to install: Attach the wall mounting bracket with bolts as shown in the assembly instructions, hang the inverter, hang battery on the wall mounting bracket, and then connect the cables from the battery and the inverter. The SMA Energy Meter is a must, of course, since it is necessary for the inverter to operate correctly. The Energy Meter provides the inverter with the current measurement data on electricity drawn from and fed into the grid.
Switch It on and Register on the Portal. Done!
The battery is ~ 25% charged by default.
Our three-person household consumes 2,800 kWh annually. Everyone should calculate out the value for their own household, however, because the numbers here only apply for my household. Our average consumption is 7.7 kWh per day. I’d like to first show how the inverter works on two typical days and what contribution the battery inverter makes.
A Sunny Day (March 10, 2014):
Both my wife and I work, so our power consumption during the daytime is very low. Once the sun was up over the horizon, my system started generating current for direct consumption. The inverter started charging the battery as soon as the energy generated was greater than our consumption. The inverter knew from experience, however, that the day was going to be sunny and that power consumption would be low during the day, so it stopped charging the battery and just fed into the utility grid. It fully charged the battery only around noon. In the afternoon, when the PV energy decreases, it switched the battery into discharge mode, as consumption began to exceed the PV energy.
We then were able to use energy from the battery until midnight. The yield was so high on this particular day that the PV system was able to cover 70% of our power consumption. Of the 5.5 kWh we consumed, we used 1.85 kWh directly from the PV system and 1.89 kWh via the battery.
Not every day this early in the year has so much sun, so I’d like to now describe a typical cloudy day, since people seem skeptical about how this will work with the small battery.
A Cloudy Day (March 3, 2014):
We got up, turned on the lights, and made coffee and ate breakfast. Of course, we needed to use power from the utility company for this, because the PV system is not able to supply enough energy in the morning at this time of year.
We went to work again, while as the first rays of sun arrived, the inverter was using meter data to analyze whether it would be able to charge the battery. The excess energy was loaded into the battery, with only a slight amount being fed into the grid. The Sunny Home Manager could have improved the inverter’s charging process even further by forecasting generation and consumption, but on this day the system worked fairly well without it. After work, in the afternoon, we cooked and consumed power for light, water and electrical devices, like all households do. The inverter switched to the battery as soon as the PV system was no longer generating sufficient power. This meant that we had power from the battery until 8 p.m., although the sun had set at 5:30 p.m. Of the 6.8 kWh we consumed, we used 1.4 kWh directly and 2 kWh via the battery. This meant that 51% of our daily consumption came from the PV system.
The aim of the system is to cover a household’s electrical energy requirements as much as possible with inexpensive solar energy produced on-site. The Sunny Boy Smart Energy manages to do this extremely well: By the end of March, I already had a daily self-sufficiency rate of 70% to 90%.
Obviously on dark November days or when snow is covering the modules, practically no electricity will be generated. However, on many days in summer, the battery will mean that I can cover 100% of my energy needs—which will pay off increasingly over the next few years.
Last year, my income from my PV system without a battery was €860.00 resulting from the advantage of self-consumption and feed-in tariff. When I compare February and March with my current configuration with a battery, the situation is as follows, if you do not take into account the increase in the price of electricity at the beginning of the new year.
These values have been read directly off the energy meter and entered in an Excel table. For more detailed information, you can contact me.
If you use the current tariffs for electricity costs (in this case 30 cents/kWh) and compensation (10 cents/kWh), the advantages of the battery inverter over traditional inverters become very clear.
The Bottom Line
It is good to see that the battery has reduced my electricity bills even further. It will be a significant advantage if the compensation drops further and the electricity costs rise again.
I hope I have given you a little insight into the Smart Energy inverter to help you make your own investment decision.
Armin Kühn (guest author)
Armin works at SMA as a developer in the system validation.