When installers plan a residential solar project that may be paired with batteries now or in the future, they must choose the right power electronics to make moving that energy around as affordable and efficient as possible. Inverter manufacturers offer plentiful options, each with their own pros and cons.
Here are the different types of inverters involved in residential solar + storage systems.
A wide range of AC-coupled inverters can be paired with more equipment to build a solar + storage system. Standard PV inverters include one input for solar panels, then feed that power to the home’s electric panel.
Battery inverters are required to add batteries to solar power systems already equipped with standard PV inverters. These devices have an input specifically for batteries. They take that AC power generated by the PV from the home’s electric panel and convert it back to DC power to be stored in the battery, then back to AC when it’s time to use the stored energy in the home. Battery inverters are used in retrofit scenarios when a homeowner wants to add storage later.
SMA makes the Sunny Boy Storage battery inverter to integrate batteries into PV projects.
“Any existing PV system that’s seven or eight years old can add our [Sunny Boy Storage] system and not have to remove what’s existing,” said Rob Lamendola, product manager of home solutions at SMA America.
Battery inverters like SMA’s have multiple battery inputs to expand the system size over time as needed. They’re also brand-agnostic, so any compatible batteries can be mixed and matched in the system.
“It’s flexible for the installer to provide a homeowner with a small system if they want a small backup system, or a fairly large battery backup system,” Lamendola said. SMA’s compatible small battery size is 16 kWh, while the large option is 96 kWh. However, SMA is not compatible with smaller battery sizes like those offered by LG and Tesla.
Enphase’s IQ8 microinverters also allow for AC-coupled storage systems, but they’re unique in that they can act as both PV inverters and battery inverters due to their bidirectional capability — they can move power both ways, from DC to AC and vice-versa. Because of this ability, they perform different functions across a solar + storage system.
At the panel level, the IQ8 converts DC solar power to AC power, then feeds it into the home’s electric panel to be used. The separate Enphase IQ Battery houses IQ8 microinverters inside that handle the power in an opposite direction, taking generated AC power and converting it to DC power stored by the batteries. When it comes time to discharge the batteries, those built-in microinverters will convert the power back to AC to run the home.
Enphase IQ8 systems allow for an even smaller option of battery building blocks, starting at 3.3 kWh.
“It really dramatically lowers the barrier to entry to enter into storage,” said Raghu Belur, co-founder and chief products officer at Enphase. “In Enphase’s case, because I have [an] AC-coupled [system], I can start small and I can come back and add more and more storage and match it to whatever …….