What Is Offset? And Why Is It So Important?



Have you heard anyone claim they went solar but still get an electric bill? Sounds ridiculous! Was their system designed wrong or does solar just not work that well?

The answer is absolutely the system design. System design is the key to how efficient your system will work. Keep reading to find out exactly what you should look out for when going solar.

A good solar consultant always discusses your electrical usage and how much the system will offset your electrical consumption. In other words, the percentage of your total yearly usage (in kWh), that will be covered by the electricity produced from your solar panels. In almost all cases where there is enough space to mount panels, you want to have a system designed to produce slightly above 100 percent. Most solar owners even have production up to 110%. This gives you peace of mind and will cover any reduced production via weather or time used.


Curious why we said a good solar consultant always discusses your system offset? The reason being that some homeowners, unfortunately, have purchased their solar panel system without ever knowing if it will cover their full annual usage. They expect going solar will completely eliminate their bill, but a system designed at only 80% offset will result in them still being billed. Not only for a connection fee to the grid, but also charges covering the other 20% purchased from the utility company.


As with many industries, there are some companies and individuals who will avoid discussing your usage offset entirely, or be misleading about it. They also might only use a month or two of your home’s electrical history to design the system, which can create a very inaccurate result.

-BEWARE OF ANY ESTIMATE USING ONLY ONE MONTH OF USAGE HISTORY-

So how do I know if my solar consultant is designing my system right? As long as you have lived in your home for more than a year, they should be inputting a full year of usage history into the system design.


Additionally, many people get quotes from multiple companies that might use different design software. Even so, if using similar equipment, the system sizes should be very close. If you have two companies quoting at 100% offset with one total size of 7-kW (Kilowatts), and the other at 9-kW (kilowatts), something is wrong. There should rarely be a size difference greater than 0.5-kW for the same percentage of offset.


The ABSOLUTELY BEST way to determine who is doing the job right, is to simply ask. Ask them to explain how they factored in your home’s energy usage when designing the system. Any true solar expert, can and will, gladly walk you through projected system outputs for the total year.

The final question to seal the deal:

Does this company offer any assurance the system they design will work properly?

Designing solar panel systems includes many calculations and configurations which need to be done with care. Solar experts that know their designs are done correctly will typically back their work and be willing to fix any issues with underproduction.


Ask, ask, ask. An expert solar consultant should be able to answer any questions you have, or at least be willing to find those answers for you.

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