Comparing Home Solar Panels: Output is King

Solar Smackown Results

You want to get wild and crazy with home solar panels. We recently reported on an installation with six, yes, count them, six different brands of solar modules. The home solar panel system has been completed and the array is up and running. So how are the panels faring? Let us compare the results 

Sanyo Bifacials

The first modules we looked at were the Sanyo Bifacial 195s. You will remember that these solar modules were used as skylights in the kitchen and bathroom of the house. Each skylight has interior walls painted white to add ambient light on the backside of the panels. One unanticipated problem with the skylights is they add additional heat to the house due to the light coming in from the southern roof.

These panels have a DC name plate output of 195 watts. Around noon each panel can generate about 200 watts of power! Not bad for the smallest wattage panel and real world insolation. And as shown in the chart below, its PTC/STC ratio is the highest of the panels we observed.  It's refreshing to see a panel make more than its nameplate wattage. This is the only panel we've seen do this and it appears that the skylight approach is working.  But as shown in the results below, over the month of testing the output, the Sanyo fared poorly in comparison with the other home solar panels we tested. Its output in terms of its PTC rating was the lowest of the panels we looked at.

PV Power 1100

The Sanyo solar panels are connected to a PV Power 1100 inverter with an optional PVM1010 data monitoring card. Central inverters are heavier and larger than micro-inverters so you need to make sure you have enough space to mount them.

One criticism of these solar inverters is that they tend to be larger and heavier (55 lbs for the PVP1100) than other central inverters. The inverter on this installation was mounted inside the garage though this is not a requirement. The data monitoring card requires a bit of setup to connect it to the inverter, but once it's installed and connected to a router the home owner can monitor performance adequately.  PV Power's inverter line is very cost effective, reliable and a common choice for professional installers.

The Solar Panel Competitors

The easier portion of the install took place with the five remaining home solar panels: Schott, Sharp, Solon, Trina and Yingli. While they are all similar in power each one has different dimensions, so a variety of clamps were employed. But they attach to a common rail, and traditional grounding lugs were used to ground each panel, rail as well as each micro-inverter to the common ground.

The Sharp 224 module is another 60-piece silicon module weighing in at 44 pounds. They are not as efficient as the Trinas(13.74% vs. 14.10%) but they are guaranteed by Sharp and made in America,Sharp electronics is a well known brand and they carry a wide range of wattages. Efficiencies are on the rise, and the Sharp 240 has a 14.7% efficiency. If I were buying Sharp I would go for the 240.

The Schott 220s have been the least powerful in this test, but these panels are also made in America at their manufacturing facility in Albuquerque, New Mexico. The Schott's are a bit heavier (50 lbs), have 3 bypass diodes and use TYCO Solarlock connectors.

The next panel in this lineup is the Trina 230 which boast a 14.10% module efficiency. The Trina's are a great value proposition and supplies of the lower wattage modules (175 and 180 watt). Trina's also provide a granular output warranty - 5 years manufacturing warranty, a 10 year 90% power output warranty, and a 25 year 80% power output warranty. When you're up on a hot roof the slightly lighter weight of these modules is welcome. The power output vs. price point below show why this panel has been popular at SolarTown.

After the Trina's are the Yingli 230-watt modules. Yingli is another Chinese module with a global reach - hence a good deal of marketing at this year's World Cup Soccer competition. Yingli also offers a 25 year power output warranty, and the modules have a 14.1% efficiency.

The last panel to report on is the Solon 220 - a German made module. We've been delighted with its performance and the 220s currently hold the performance edge in this test. The 220s only have 13.41% module efficiency and they are marketed as a very good low light module. The 240-watt modules have 14.63% efficiency. The product warranty is 2 years (compared to 5 years for Trinas and Yingli) but the power output warranty is the same. Solon clearly is making a quality module and is the current leader in power production in this test.

As shown in the chart above, these panels are comparable in terms of both their nameplate rating and their PTC rating, although the Yingli PTC rating exceeds the standard of the other panels, and its PTC/STC ratio was the highest of the brands we tested. Consequently, we would have expected that the Yingli would have performed the best in terms of output over its competitors. We were wrong! Strangely enough, the STC rating seemed to be a better predictor of output than the "laboratory-tested" PTC rating. These five panels all performed consistent with their nameplate rating, although the Solon and Sharp did better than the rest. The Solon panels, the Sharp panels and the Trina panels all performed at a comparable level in terms of output based on their PTC rating.  And as shown in the chart, if you are buying primarily based on price and looking for discount solar panels, you would have to take a hard look at the Trina and Yingli.

Some Final Observations

The panels you choose depend on your objective. The Sanyo bifacials are in a class of their own as they serve two purposes - generating electricity and letting in light on an otherwise covered area. Everyone who visited the open house admired these unique skylights.

Speaking of manufacturing, many solar enthusiasts are partial to supporting the National Economy - in addition to the Sharp panels, SolarWorld panels meet this criteria. Remember that you'll have your panels for about 20-years so the time you take to consider what your final array will look like is important. The best solar energy systems have the least amount of parts showing beyond the panels. This isn't always easy to achieve, but if you move ahead with an installation carefully consider where all the support pieces will reside. Keep an eye on this array as you wish and contact us when you're ready to discuss your own project!