Avoid these 4 Common, Costly Mistakes When Going Solar


Avoid these 4 Common, Costly Mistakes When Going Solar

Avoid these 4 Common, Costly Mistakes When Going Solar

Going solar reduces your carbon footprint and should save you money on your overall energy costs, too. But that’s not always what happens. Homeowners who install solar often do not see the promised savings because of four common mistakes.

Mistake #1: Wrong System Size

Many solar companies use very rough, inaccurate methods for sizing and configuring a new solar installation. In the worst cases, they base their calculations on the average dollar amount of your electric bill. More sophisticated solar companies will use the total amount of kilowatt hours your home has used in the past 12 months.

The problem with both of these methods is that they suffer from averaging errors. Homes do not typically consume the same amount of energy every month of the year, and solar installations do not produce the same amount of energy every month either. In both cases, there is seasonal and environmental variability that affects your home’s production and consumption.

The best way to size your solar system is to use your home’s hourly usage data, overlaid with hourly solar energy production data that incorporates climate and geography information, and then rating your net consumption to find the utility rate plan that will generate you the most savings on your electric bill.

If your solar installer did not use this data to size your system, then there is a good chance that you have installed more solar than you need. This is because solar companies charge by the amount of kilowatts installed, so the tendency is to sell larger systems. Additionally, a larger system will provide extra “insurance” that the homeowner’s electric bill will be fully offset, effectively masking their size calculation errors.

Homeowners with oversized systems have reduced savings, if there are any savings at all. All their extra electricity production is often sent to the utility for free, without the homeowner even realizing it.

Sometimes solar companies will install systems that are too small. Unless these systems are installed during initial home construction, the economics of small systems tend to not be favorable to the homeowner. This is because of all the fixed costs associated with installing any system (permitting fees, site inspections, engineering plans, etc.). Fixed costs can offset the economic benefits of small installation so much that your total energy costs might actually increase.

Mistake #2: Wrong Direction

With new “time-of-use” rate plans available (and eventually to become mandatory), when your solar panels produce energy becomes almost as important as how much they produce.  

Most solar companies recommend installing panels on south-facing roof sections. While it is true that in the United States (and everywhere else in the northern lattitudes), south-facing panels produce the most electricity overall, more westerly-facing panels can actually benefit you more financially with certain utility rate plans.


Typically, the grid is most heavily loaded in the late afternoon and early evening. West-facing solar panels produce more electricity later in the afternoon than panels facing any other direction. By producing electricity when the grid needs it most, you will be rewarded with a higher bill credit on certain “time-of-use” rate plans because you’re helping to offset the increased demand.


East-facing panels produce the most in the mornings, but that doesn’t help offset the grid’s afternoon demand, so you get a lot less credit on your bill from panels that face east.


GOLDILOCKS ZONE: Southwest. If you want to generate the most electricity at the most valuable time of day, you should install panels on a roof that faces halfway between south and west.

Mistake #3: Wrong Rate Plan

Most homeowners don’t realize they have a choice with their utility rate plan. Fewer still know which rate plans will be most advantageous for them, particularly after they install solar panels.

The default rate plan that is automatically assigned by your utility is generally not the most favorable for solar installations. How and when your home produces and consumes electricity determines which rate plan will reward you the most for your solar production.

So how do you decide which rate plan is best for you? Here are the choices from Southern California Edison.


          Domestic (Default)                TOU-D (A)                          TOU-D (B)                          TOU-D-T

Rate plans are complicated, and they tend to change every few months. You can request a re-rate analysis from your utility to help you decide if a different rate plan will save you money (assuming your home usage patterns remain the same).

Sometimes there are restrictions with changing rate plans. For example, with SCE, you may change to a “time-of-use” rate plan, and then switch back to your old plan if you change your mind. But after that, you won’t be able to make another change for 12 months.

Mistake #4: Loose Wire

Manufacturers guarantee output from their equipment. However, if your installer failed to connect all the wiring, you could find a lot of panels are not generating electricity.

The best way to prevent this from happening is by including a solar production monitoring system with your installation. A monitoring system will let you know right away if your panels are not producing as expected and help you track the performance of your solar panels over time.

You can easily avoid these mistakes.

When installing solar, insist that your solar installer use hourly data to properly size your system. They should also base the size on which rate plan is most advantageous for your home’s energy usage patterns. Have them include a solar monitoring system.

Then after your installation, sign up for our Solar Savings Maximization service so that you can get the maximum savings from your solar investment over the life of your system. We’ll make sure your solar installation is performing as expected, and ensure that you stay on the most advantageous utility rate plan.

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