Solar developers define the size of a solar farm in terms of its capacity–how much energy the entire farm can produce at one time. This is measured in watts, just like a lightbulb in your home. Most solar farms produce over one million watts, so the shorthand “MW” (megawatt) is used to express the size of a solar farm.
1 MW = 1,000,000 watts
A solar developer might say, “We’re building a 25 MW project,” which means that this particular farm can generate up to 25,000,000 watts of energy at one moment in time (at high noon on a sunny day).
To make things a little more complex, it’s not always clear when you hear “100 MW” if that’s DC or AC. Solar panels generate electricity in the form of direct current (DC) but our electric grid–and everything in your home–runs on alternating current (AC).
That’s why solar farms incorporate large pieces of equipment, called inverters, that convert DC to AC so the electricity the farm generates is usable by homes and businesses. Some energy is lost in that conversion–generally between 15% to 20%. So, a solar farm with a capacity of 100 MW of direct current (100 MWdc) generates roughly 80-85 MWac.