When you’re discussing the details of a solar energy system, it’s easy to slip up in embarrassing ways. Even solar company CEOs commit common mistakes, says Sean White, instructor of HeatSpring’s 58-hour NABCEP Advanced Solar PV Training Series.

His courses teach students how to avoid these slip-ups. They also teach electricians, contractors, or people entering the solar business how to design, install, and sell solar PV systems. 

“Sometimes even the CEOs or others in positions of power at a company don’t fully understand the industry, and in some ways don’t really understand what they are selling,” says White, who was the Interstate Renewable Energy Council Trainer of the Year in 2014. He is an ISPQ Certified Solar PV Master Trainer and the author of numerous books about solar energy. 

“CEOs will come in and think they’ll be able to turn a company around, but they end up running it into the ground because they don’t really understand electricity or how solar systems go together,” White says.

Understanding Power vs. Energy

One of the most common mistakes is confusing energy with power. “One of the big embarrassments is when people talk about electric bills and they talk about the kilowatts (kW) they use. Kilowatts are power, not energy, and what they really mean to say is kilowatt-hours (kWh), which is energy. They need to know the difference between power and energy,” says White.

Power is the rate of electricity produced by a system, and it is expressed in kW. Energy, on the other hand, is expressed in units consumed over a specific time period, or kWh. That’s what appears on an electric bill and reflects a consumer’s usage.

Do Your Homework about PV Ratings

A second common mistake is assuming a PV system will constantly put out as much energy as the system’s rating, says White. For instance, a 5-kW solar system will never produce 5kW all day long and will likely never produce 5 kW. That’s because PV systems aren’t exposed to ideal solar conditions all day every day, explains White. The “5 kW” rating assumes that the system will yield 5 kW if all solar conditions are beyond optimal for the system.

“Those optimal conditions that were tested in the lab don’t really exist in the outside world. The systems will have inverter losses, to start,” says White. Cloud cover also affects their output.

Certain modules are about 10% more efficient than other modules, watt-for-watt, says White. For this reason, it’s not only important to understand the meaning of a 5 kW rating; it’s  important for buyers to do their due diligence on solar module manufacturers. This can have a big impact on a solar project’s efficiency.

Is Energy Storage Appropriate for All Solar Systems?

A third common mistake is assuming that energy storage will boost a project’s benefits and pay off quickly. But does it always pay to add storage to a solar project? It depends largely on the incentives and regulations available, says White. 

“People think they can just run their house on batteries, but the truth is in most places you are going to lose money on the battery. Depending on where you are, batteries can be more of a novelty and really a money-killer as opposed to a good fiscal decision. The battery has losses, and in most cases the battery can’t beat the efficiency of net metering,” says White. With net metering, the utility meter runs backward when a solar system is generating KWh. If you add a battery, it can store solar energy for release at night. The battery financial dynamics are however changing fast.

Whether you’re a solar installer, CEO, or electrician, avoiding these common mistakes can boost your credibility, confidence–and ultimately, earnings.