Solar System Sizing Myths

My solar system can be sized based on my home’s square footage and monthly electrical costs.

With the rise of mass-produced everything (from food to clothing to electronics) it is easy to assume that a solar system works the same way.

However, because of the sheer number of variables it is almost impossible to provide a cost estimate without at least some analysis. The “average” American home uses 830 kwh of electricity per month. But that number doesn’t mean much to your solar installer – remember, averages are just adding together the available bills and dividing by the number of homes. An average doesn’t account for your region, electrical usage, habits, priorities, base fees and taxes, or your power needs.

Your home’s square-footage doesn’t tell us about the availability of sunlight, roof space, and electrical system. All of these are vital to understanding how a solar system will work for you. Two identical homes can have very different power needs based on the people and activities going on inside them! Because all of these things affect the design of your solar system, and can’t be accounted for without looking at your annual electrical usage or a detailed analysis of all of the electricity using items in the home. A solar system designer looks at your electrical information and then compares that to the available roof space, local regulations, and utility policies to create the best system for your needs.

I can’t start small and expand my system later.

Newer technologies have allowed solar to overcome previous limitations. Older equipment used to make it challenging to add on additional panels when you needed more power (or have a bigger budget). New microinverters make it easy to start small and increase your system as you choose. And if you have a solar system with battery-backup for emergencies, unlike other types of solar batteries, newer lithium chemistries allow you to add additional batteries to an existing battery bank if you find you need need more energy storage.

Whether its planning for new electric vehicles, a new hot tub, or scaling up as your budget allows. Tell your installer about your plans so they can help you design a system that will always meet your needs.

I should size my system larger than what I need so I can sell power back to the utility company.

A common misconception is that you can go solar and sell electricity from your solar to your utility company and make a profit. However, it is very rare for utilities to pay for excess solar production from residential systems. Net metering, the most common relationship between a solar adopter and their utility, does allow solar customers to use their grid connection like a bank account to “store” energy credits for later use, but it is usually a condition of connecting to the grid that the utility will not reimburse their clients for excess production (usually annually). Many even have limits on the maximum size system that can be installed based on your historical usage for this reason.

I need solar trackers on my system to get the most production possible so I can have a smaller system.

While it used to be that a solar tracking system that allowed solar panels to follow the sun’s path across the sky would dramatically increase the efficiency of the system, and therefore it’s monetary value, this is no longer the case. As panels have become more efficient and microinverters have allowed stationary arrays to deal with differences in shading, trackers have become much less useful.

As with any technology, the more moving parts a piece of equipment has the more likely it is to break. To utilize trackers, you also need a pole-mounted system. This type of mounting is more expensive than traditional roof mounting with no additional returns. So, it is better to choose a slightly larger system size without trackers to maximize your energy production per dollar invested.

I can keep my whole house running with a large solar and backup system during a grid outage.

While at its core this statement is true, most people looking into going solar do not have the budget to be able to back up an entire home’s electrical usage. It is less of an issue of design or sizing (although some homes do not have an electrical system that will allow for a complete backup of power) than it is of the basic economics of backup power systems.

Financially it frequently makes sense to invest in a backup power system that will prevent food spoilage, costly medical bills, or major inconvenience (such as losing access to a well pump). There is less of a return on the power stored to say, power to run your dishwasher, three TVs, computers, or your hair straightener. Most of these items can be done without for the short periods that usually characterize most grid outages. The amount of investment upfront to be able to power a full home is usually not only cost prohibitive, it generally does not show any additional returns than an essentials-only backup system. Invest wisely in an appropriately sized backup system for the greatest benefit.