DC to AC Conversion Losses and Choosing an Inverter

The question that arises often when purchasing a solar system is:, why would I buy 10,000 watts of DC (Direct Current) solar panels and then only buy an inverter that has an AC (Alternating Current) output of 7600 watts? To understand this, one must first understand that solar photovoltaic panels make DC electric power. America’s grid that powers our homes and businesses is run on AC electric power. The conversion from DC to AC is done by a device know as an inverter. There are losses that occur during the process of converting from DC solar power to AC power on the grid. (See grid below)

The next part of the equation is to understand what it truly means to have, for example, 400 watt solar panels in your photovoltaic system. The 400 watts is the best case scenario that this rated panel could produce instantaneously if the panel was installed in the most optimal angle to the sun and stayed optimal all day / all year long. In reality we all know that as the sun tracks east to west over the course of the day the angle that it’s light (actually photons) strikes the solar panels changes continuously. Thus, there are only a few optimal hours in the middle of the day for your solar system to collect maximum power.

Also consider that the sun’s track in the sky is either higher or lower due to seasonal changes which also alters the angle the photons strike the photovoltaic panels. In reality a 400 watt panel will likely never produce 400 watts of DC on your roof as the sun angles will rarely if ever be optimal as when the panel was flash tested in the factory. The factor flash test rating is simply a standard in which the industry can measure and market the theoretical capability of a specific photovoltaic panel.

So in choosing an inverter system that best optimizes the solar panels chosen the decision comes down to: does one want to spend more money today for a larger more robust inverter that is capable of maximizing the peak power output that only occurs a few hours a day a few months a year; or does one wish to purchase a smaller inverter and save the money up front knowing that it may not convert the full potential of DC power during the peak sunlight hours of certain months of the year?

The charts below depict the actual dollars of lost revenue that a smaller less powerful inverter system would not convert to AC, known as clipping, so one can assess the value proposition of spending more money up front to create more value over time. With return on investments being 17-19 years many may say the value of the larger inverter is not a wise financial decision. Others will say an extra $1000 or so in the scheme of the total system cost is a small additional cost and well worth the expenditure to make extra power that does not need to be made from burning fossil fuels.

Now with this knowledge any consumer will be better able to make an informed decision that meets their individual goals. You can always get in touch with our team for more information.