If you’ve done any research into rooftop solar systems for your home, you’ll notice a lot of “average system size” numbers tossed around. The Center for Sustainable Energy puts the average residential system size at 5kW, as do many other sources. However, averages are only so useful when determining the proper system size for your home. Let’s take a look at what information you’ll need to get an accurate assessment for your unique needs.

Your Old Electric Bills Can Help You Design Your New Solar System

The first thing you’re going to want to check is your current and historical energy usage. Unless you plan to change your electricity usage radically upon your upgrade to solar, historical data will be the best indicator of future usage, which provides a basis for determining system size.

Another Factor in Solar System Size: Month-to-Month Differences in Sunlight

Even Los Angeles, which gets about as much or more sun as any place in the US, has monthly variations in sunlight. Generally speaking, comparing solar power generation in summer vs. winter, you’ll get more sunlight and power in summer, but exact power generation varies on a month-to-month basis. Take a look at the following estimate from the National Renewable Energy Lab’s PVWatts Calculator to get an idea of how much your power generation can jump from month to month.  

Source: National Renewable Energy Lab (NREL)

The energy production estimates listed are based on a 5kW solar system installed in the Los Angeles Area. Looking at the AC Energy column will give you an idea not only of how much your energy production is likely to vary by month, but also starts to give you a ballpark idea of how big your system should be. If your current and historical energy usage figures are similar, you’ll know you’re pretty close to the average.

Other Factors That Affect Solar System Size

Calculators and averages can tell you a lot about what size solar system you’ll likely need, but the bottom line is that honest, accurate estimates require custom installations optimized for your home and its exact location. That’s because so many other factors are involved. These include:

  • Attic access and suitability, if an attic run is being considered
  • Budget
  • Electric main panel condition, sizing, and open breaker slot availability
  • Financing
  • HOA codes (if applicable)
  • Local codes
  • Offset power amount desired
  • Panel efficiency
  • Panel power rating
  • Roof condition, measurements, obstructions (e.g. vents), orientation, space and type;
  • Shading

If your home’s roof has a distinctive design, like Victorian cupolas, that’s going to affect where you can install solar, and what type of photovoltaic array you use. Smaller areas require higher efficiency panels to achieve the same results compared with larger arrays of standard panels. Similarly, you may want solar shingles instead of panels, depending on your aesthetic preferences and budget.

Part of why LA Solar Group can back its installations with 25-year warranties for power production is that we consider all of these factors when helping you design your rooftop solar system. Taking all of these things into account enables us to create highly-accurate estimates of how much power your system will generate over time; if the system fails to perform as predicted, we will upgrade your system as needed, and compensate you for any shortfalls.

As you might imagine, LA Solar Group has deep experience in optimizing solar systems for specific locations, power and aesthetic requirements for Greater Los Angeles-area homes. We have helped more than 2,200 homeowners go solar, each backed by our 25-year solar system warranty. If you have any questions about what size and type of system would best suit your needs, just let us know.