Written on behalf by Madeline Acri, National Energy Storage Specialist at Soligent
Once upon a time, long ago in the 1980’s net metering began its adoption amongst utilities in the US. This policy enabled homeowners to get paid back for the energy credits their solar arrays produced when feeding the grid. Now, depending on which state you live in there may be a cap to how much energy you can backfeed and be credited on. Where I live in Austin Texas, Austin Energy limits your solar array size to roughly 110% of your previous year’s energy consumption. When sizing PV based on a grid-connected system, there is some nuance to the DC size of your solar array as it relates to the AC output of your inverter. Inverters have a nameplate rated output and cannot produce power higher than that kW level for a prolonged period of time. However, this does not mean that your PV array is limited to this kW size. In fact, the PV should be sized larger than the inverter to account for higher production opportunities during low light events which occur in the morning and evening. Oversizing the PV for grid-up circumstances can help increase your solar production any time that is not high noon. The sizing tactics change even more when a battery is added to the mix. Now, we want to consider powering the house loads AND charging a battery bank in the event of an outage. This would encourage even more PV to be added to the system despite the grid-tie inverter output being much smaller than the PV kW size. Depending on if you use your battery frequently for self-consumption purposes or rarely in the event of a prolonged power outage, you may want to add panels according to the depletion levels of your battery bank. This will be discussed in more detail during the upcoming Storage Webinar series.