Advantages of Solar Power: Microinverters or String Inverters
We've been in the solar business for a few years now. As such, we're fortunate enough to see plenty of solar arrays. Here's one I came across the other day: Blue sky, green trees, and a 15-module solar array. And outside the frame: one proud owner with jealous neighbors.
We love solar so it's something we never tire of seeing. But if you're like us and you think about solar long enough, and see enough installations, you begin to notice the little things.
Take this picture for instance. Look closely and you'll notice a problem lurking in the shadows. Literally in the shadows. It's a big problem and something we see all too often: shaded solar panels. And not just shaded solar panels, but inconsistently shaded solar panels. Not good. Arguably, this solar system could have been installed much better.
Shade on solar panels is bad news. Traditionally solar panels work much like the batteries in your boombox. While you might have 5 brand-new batteries, it's that 6th D-cell, the dead one, that's preventing you from blaring In Your Eyes at your girlfriend's window.
Solar panels historically work in much the same way: you might have 5 solar panels basking in the direct sunlight, but it's that proverbial 6th one in the shade that's bringing down the whole system.
Despite the cloudless sky, the system above is essentially offline, currently generating about as much electricity as the solar panels on your calculator. Problems like this account for significant losses in production and revenue. We hate to see it happen.
Fortunately we started to see a big change about 19 months ago. Microinverters started taking the market by storm. Leading the charge is the Enphase M215. It became our #1 selling inverter soon after we started carrying them in June 2011, and remains so today.
Microinverters allow solar panels to operate independently of each other. So if one module ends up in the dark, the others just keep on buzzing, resulting in much higher average system availability. That's especially great news for residential solar arrays with inconsistent shading profiles, such as the typical one pictured above. Chimneys, trees, dormers, and snow are among the biggest factors culprits inconsistent roof shade.
Let's revisit the picture above. Shade is covering the better part of 4 panels in a 15 module system. Assuming this system is configured with a traditional string inverter, then it's bad news for this homeowner — this system will be generating no power at all. However, if the system is configured with microinverters, then only the 4 shaded modules are offline, while 11 panels are working flawless in the the direct sun. Or 73% of it's capacity. That's better. It's numerous, random variations from house-to-house, like the one illustrated above, that make it hard to exactly quantify the shade problem. But industry estimates suggest that microinverter-backed residential solar systems provide up to 16% more production than their string inverter-backed counterparts. That means generating 16% more electricity, and 16% more dollars in your pocket, just by using microinverters.
Got shade? Got dormers, chimneys, leaves, or snow? Installing modules on multiple roof facings? Use microinverters.
There's other benefits to microinverters too. Traditionally strung solar arrays have losses due to module mismatch, connections, and DC wiring runs — none of which are part of a microinverter-based system. Plus there's no single point of failure with microinverters. As you can tell, we're big fans.
Enphase microinverters are very popular. They're an industry leader for good reason: high conversion efficiency, competitive pricing, 25-year warranty. Plus they have great monitoring software tracking the output of each module on your roof in real time. It's awesome! Here's a few screenshots based on a system we commissioned in Hawaii.￼
Enphase software provides real-time monitoring of each module in your system, and the system as a whole. Plus it tracks the performance over time, which is great for bragging about your carbon offset.
Want to keep close tabs on the performance of your solar system? Use microinverters.
Enphase isn't the only player in the world of microinverters. We were happy to hear that Helios partnered with Exceltech to offer true AC modules — where the inverter is built into the panel at the factory. That's good news for cutting down installation costs. We're big fans of Helios — our neighbors making great modules right next door in Wisconsin. Their decision to go with an on-board microinverter is smart and simple. It's improvements like this that will change typical system installation times from days to hours. That means big savings in labor passed on to you — the homeowner. It's going to make a big difference in solar.
Microinverters are the future of solar — smart & simple, efficient, reliable. We exclusively use Enphase M215 Microinverters in all of our JuiceBox offerings.
Considering solar for your home? Got shade? Want bragging rights? Get microinverters. And, of course, work with great local installers who know what they are doing.
- Customizing PVWatts calculator [nrel.org]
- PVWatts Calculation Values with an Enphase Microinverter System [enphase.com, PDF]
- PVWatts Calculator — Version 1 [nrel.gov]
- Helios AC Module [heliossolarworks.com]
- Enphase tracking software — Public Systems [enlighten.enphaseenergy.com]
- Say Anything. Starring John Cusack [wikipedia.org]
- The Enphase M215 Microinverter [enphase.com]
- Small is better [pv-magazine.com]
- Enphase Microinverter performance [enphase.com]
- Enphase Performance Handout [enphase.com, PDF]
- Microinverters versus String Inverters [yougen.co.uk]
- PV Micro Inverters and Optimizers: Not Just for Lazy Designers [renewableenergyworld.com]
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