Megawhats? Kilowatts, Megawatts and Solar Terminology

February 7th, 2013 |
REC Solar has now built more than 9,000 solar electric systems across the U.S. totaling 143 megawatts. Last year alone our company built more than 50 megawatts of solar in 15 states. These are impressive numbers, but might not mean much to those unfamiliar with solar’s terminology. What is a megawatt, anyway?

Let’s start at the beginning. All solar panels have a “nameplate rating,” which describes the panel’s optimal output in watts. If a first-tier monocrystalline solar panel has a nameplate rating of 260 watts, under perfect conditions this panel would produce electricity sufficient to power almost six 45-watt compact fluorescent light bulbs.

Of course, solar panels rarely operate under perfect conditions. That’s why the many different solar panels on the market are tested by the California Energy Commission to account for dust, wiring losses and weather, among other factors. Looking at the Commission’s website, we see that a 260-watt solar panel can actually be expected under less-than-perfect conditions to produce around 234 watts.

Each solar system is individually-designed and sized to meet the specific electricity demands of the customer, but most residential solar systems are around 6,000 watts, or six kilowatts. Thus, the average residential solar system consists of 25-30 solar modules. Such systems often fit readily on a standard residential roof, but can also be mounted on the ground. Examples of six kilowatt systems follow:

A 6.6kW solar system in Santa Maria, Calif.

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A 6kW solar system in Scottsdale, Ariz.

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A 6kW solar system in San Luis Obispo, Calif.

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When we make reference to a megawatt (1,000,000 watts) we’re talking about the functional equivalent of 150- 200 residential systems, or a lesser number of larger commercial solar systems. Indeed, REC Solar has built systems up to and over one megawatt for large multi-national businesses – including Costco, IKEA, Nestle and DuPont – and agencies including the Departments of Veteran Affairs and Defense, which use solar primarily to control energy costs. A one megawatt system typically uses around 4,000 individual solar panels and if mounted on the ground (not many facilities can host such a sizable system on the roof) utilizes approximately eight acres. The following are two examples of REC Solar-constructed one megawatt systems:

A 1.16 MW solar vineyard installation at Castle Rock Vineyards.

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A 1.2 MW solar installation at Kapa’a, Kaua’i, Hawaii.

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When we say we’ve built more than 50 megawatts in 2012, in truth that number consists of many residential solar systems, and a smaller number of mid-sized, large, and very large commercial solar systems. With the price of solar continuing to drop, and electricity prices increasing in many states, we look forward to an even more successful 2013.

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