Can I Add Solar Panels To My System?
Properly estimating the needed wattage of a residential solar system should be pretty straightforward when working with a knowledgeable consultant. It can be complicated, however, in cases where the homeowners have less than 12 months worth of energy usage, or in situations where the number of residents in the household grows, or the home uses more energy for any other reason. For these reasons and others, you may find it necessary to add panels to your existing solar system. Is it possible? Usually, but the ease with which you can add panels will depend on what type of system you’re starting with.
DIRECT CURRENT (DC) PANELS
If you’ve elected to put DC panels on your roof it is possible to add, but there are a few conditions that need to be just right. Installers need to “string” a direct current system together and connect groups of four panels or more into one inverter. That inverter contains a “strike voltage”—a voltage level that must be met for the inverter to activate and produce solar energy. To ensure the strike voltage is reached, it’s essential to place each panel in a given string at the same azimuth (angle to the sun), so that the panels are all maximizing solar rays at the same time rather than hours apart, as they would if facing different angles or directions.
Each DC panel is only as strong as the weakest one in its string, which means shading is nearly as important as angle. Whatever is hindering the production of your panel, that reduction will be multiplied by the number of panels connected to the single inverter they share.
An additional barrier, though not an engineering one, is that California instituted a new regulation in 2017 to mandate that all strings of panels have an independent rapid shutdown, which is a failsafe in case of fire or other emergency.
Finally, as you may have guessed, because DC panels must be added as a “string,” additions are often made in increments of four panels or more. If you’re looking to add currently and have DC panels, your first step should be to check that you have enough available roof space on one plane, not broken into differing angles and directions.
ALTERNATING CURRENT (AC) PANELS
If you’re not using DC panels, you either have AC or panels with “microinverters”. Essentially these function the same—both use a single, smaller inverter per panel to change direct current to alternating current. The difference is that the AC modules have their microinverters integrated into the panel itself, while the other varieties have the inverters attached to the racking.
Details aside, the big picture is that unlike DC panels, AC and microinverter modules do not need to be added in bunches as part of a string. First and foremost, this frees homeowners up to add as few as one panel at a time. That’s convenient for those who are going solar without the benefit of having 12 months of energy usage on hand to accurately predict annual wattage output, meaning you can be conservative with your initial system and add as needed.
AC and microinverters alleviate some of the major challenges common to DC, as well. Because each panel is essentially independent, rather than part of a string, there’s no concern about which angle and direction each panel faces, and no concern over strike voltage, purchasing rapid shutdowns, or the group of panels under producing because of a single poorly performing panel.
WORD TO THE (ENERGY) WISE
Some systems are easier to add to than others—even among AC and microinverter options. If you’re new to your home and trying to get ahead of nasty energy bills, be sure to discuss your plans to start conservatively and add to your system with your solar consultant.