It's a trade off. Efficiency will improve in the summer as the panels heat up and the loaded voltage drops on each panel. On a hot day the panels will rise at least 17C above the 20C test temperature. This temperature rise drops the total panel voltage by almost 6V. Shown below is a block diagram of the home system. The inverters now talk to a PC to provide real time data of output current and total AC power.
Batteries are big, heavy, and add a few dollars to the system cost.
If you only want the maximum power from your solar system at the lowest cost, batteries are not needed. Using a special version of the inverter that runs without batteries results in a simpler and more efficient system. The batteries, charge controllers, battery disconnect circuit breakers, and secondary circuit panel are all eliminated. The special inverter also has special software, power tracking software, that optimizes the system for maximum power from the panels. With a battery system the voltage of the panels must be larger than the voltage of the batteries.