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Let's talk about efficiency first because my first instinct was to try to find the panels with the highest efficiency. Most panels are around 13 to 15%, but there are higher panels out there. In the lab, scientists have even developed panels that are 40% efficient! The higher the efficiency, the higher the cost. Just keep in mind that higher efficiency doesn't mean the panel is better - it just means that your array can be smaller because your panels are producing more power per square inch. I quickly decided that I wanted panels in the 300-watt range so that my array could be as small as possible. The highest panels on the market were 320-watt panels made by Kyocera with an efficiency rating of 16.10% but they were 1/3 more expensive than the 310-watt panels and that small increase in efficiency isn't enough to justify the greater cost, in my opinion.
It quickly became apparent that I needed a spreadsheet to store all my comparison data:
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By the way...I normally like to buy American but this is one area where it's next to impossible. Sharp has just announced that they are no longer going to be making panels in the U.S. SolarWorld panels are American-made, but a little pricier and hard to get your hands on. Be careful about the naming, because Canadian Solar panels are not actually made in Canada!
The next thing to consider is the inverter, or the device that converts the DC power generated by the panels to AC power that is used inside your house. This is where I started to get really nervous about trying to piece everything together myself. I knew that we wanted a grid-tied system, but I really wanted a turnkey system where I knew all the components worked with each other. WholesaleSolar.com is a great resource for this: you can choose from their grid-tied systems or off-grid systems at different sizes. There are 3 types of inverters: string inverters, Enphase (the most popular) or SolarEdge. If you click on the "grid-tied system" link above, you can read about each one.
Again, the key is research, research, research and I was actually considering Enphase until I started reading real-life experiences like this discussion where a solar installer that installs both Enphase and SolarEdge systems had this to say about the reasons why he thinks the SolarEdge system is better:
- Better performance. The popular Enphase M250 micro inverters are rated for 250 watts maximum. So, while they can be used with the higher-watt panels (like the 305-watt panels we're installing), you're only going to get 250 watts (+ or - 5%). With an average of twenty micro inverters in a typical system, that adds up to a tremendous loss of power over the life of your system. The SolarEdge power optimizers have a greater maximum output rating of 300 watts (+ or - 5%). Granted, solar panels rarely put out 100% of their rated power, but I'd rather be sure that there no bottlenecks under ideal conditions.
- Better efficiency. The Enphase 250 is only rated for 96.5% maximum efficiency, whereas SolarEdge offers 98.3%. Over the life of the solar array, this difference in efficiency will add up to a considerable amount of power.
- Earlier power production. The Enphase 215 requires that panels reached 22 volts before they begin producing power, whereas SolarEdge begin producing power with as little as 5 volts. The Solar Edge solution provides power when the array is partially shaded and extends the power production window to earlier in the morning and later in the afternoon.
- Cost. We paid $85 for each SolarEdge Optimizer but a comparable Enphase M250 costs almost twice as much at around $166 each.
- Better reliability? There's alot of discussion about Enphase's use of electrolytic capacitors in their microinverters. Apparently this is a problem in rooftop installations where high heat can cause the capacitors to fail. We won't have that problem since we're mounting on the ground and will have plenty of airflow around the electronics; however, I'd rather not have to worry about it. SolarEdge doesn't use electrolytics, which may be why they offer a 25-year warranty on their optimizers. One note of caution here: most, if not all, manufacturer warranties do NOT include the labor needed to replace failed components. If you've got panels mounted on your roof, you'd have to pay someone to remove the panel, replace the failed component, and then remount the panel for anywhere from $300 to $500 (or do it yourself)
WholesaleSolar.com was awesome to work with as we went through the evaluation process and it was clear they knew what they were talking about. They even assigned us a technician that was familiar with our utility rebates and requirements, which was really helpful. He was kind enough to do a custom quote that allowed us to take advantage of a deal they had for cheaper prices for panels bought by the pallet. (We only needed 32 panels, but we purchased 40 to get the better price - the others will be used on the farm or added to the array later in the future). They spec'd out the inverters, wiring, rack mounting and everything we needed to complete the array. We were even able to get 50% off the cost of the racking because of a promotion they were running. In the end, this is what we ended up with:
That's delivered to our doorstep. The only thing not included are (1) the conduit to bury the wire from the array to the house and (2) the pipe that will support the array. Rather than pay shipping costs for that, it makes more sense to buy it locally. Not including those costs, with the $2.00 rebate, we'll be getting back $19,520. So that means we have $85.95 in unreimbursed costs (of which we can get 30% back as a federal tax credit!)
This is a really long post, so I'll close for now. But I'm happy to answer any questions you might have...just leave me a comment below!
If you're interested in more on our solar project, please check the "Solar Project" section on the bar to the right.
I've shared this post with this week's Home Acre Hop. Lots of interesting stuff going on over there, guys...