Home editor's blog on going solar Celebrating one year with home solar

Celebrating one year with home solar

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We've had a 5.59 kW solar system on our Aurora, Colo. roof for exactly a year. In that time, we've produced about 8,700 kWh, enough to power 100-percent of our home electric use AND 18,000 miles of driving in an electric car.

editors-blog-entry3We’ve officially had solar on our roof here in sunny Aurora, Colo. for one year now. That means it’s time to make notations on what we’ve accomplished, reflections on what we’ve learned, what we would have done differently, what we love about being a 100-percent solar household, etc.

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What we’ve accomplished
Let’s start with what we’ve accomplished with our 5.59 kW REC Solar installed 26-panel system, for which we ended up paying an amazing and, unfortunately for others out there -- who I wish could also get as good a deal as we did -- pretty much unbeatable $8,000 in out-of-pocket costs:

  • Produced lots of electricity. We produced 8,670 kWh of electricity, or about 800 more kWh than REC Solar predicted we would in what was probably a somewhat conservative annual “System Performance Analysis” we received prior to our system’s installation.

  • Used relatively little electricity. Our family of four used 3,522 kWh of those 8,670 solar-produced kWh to power 100 percent of our pre-electric car household usage (will production EVs capable of fitting a family of four EVER get to Colorado!?). This averages out to 293 kWh per month, again pre-electric car. Not bad for a family of four, eh? Our yearly kWh use total would have cost us about $400 if we’d had to pay our utility, Xcel Energy, for it.

  • Over-produced electricity. We over-produced by 5,148 kWh and banked those hours with Xcel Energy for future use. By the way, 5,148 kWh is enough to power an EV such as a Nissan LEAF about 18,000 miles (3.5 miles per kWh), or about $2,700 worth of “gasoline” (25 mpg/$3.80 per gallon). I’m guessing that never before in its history has Xcel had a residential customer bank so many extra solar kWh in a single year. Unfortunately, thanks to Nissan’s glacially slow EV rollout, we’ve got thousands more banked kWH to go before we'll actually have an EV to plug in here in Aurora, Colo. Sure hope Xcel doesn’t pull the rug out from under us and suddenly change its policy!

  • bvProduced net electricity 12 months of the year. We overproduced solar kWh in every single month of the year, including December, a low-sun and high electric use month in which we produced 450 kWh and used 410 kWh. In May of 2011, we produced more than four times as many kWh as we used, pumping out 840 kWh while using just 186 kWh.

  • Reduced our carbon footprint. We prevented approximately 15,000 pounds of CO2 from being released into the atmosphere. To be fair, some CO2 was generated in the production of our system, its transportation, and its installation. So we might not be quite there in terms of system carbon payback yet. Then again, we might be, because our REC Solar panels were made in Sweden, where a high percentage of energy is produced by emissions free hydroelectric power.

  • Reduced local air pollution. We prevented the release of significant amounts of sulfur dioxide, nitrogen oxide, particulate and mercury pollution, pollutants coal-fired power plants pump out in large amounts every year.

  • Inspired our neighbors to go solar. Neighbors of ours who have an even better shade-free south-facing roof than ours (it’s got a higher pitch than ours and essentially is never shaded, even in the winter) went solar with a 5.1 kW system exactly a year after we did. They told us they did so in part because we inspired them with our example.

What we learned/would do differently

  • Go with a microinverter rather than a central inverter system. We have so-called string system with a central inverter. It’s performed well, even outperformed REC Solar predictions. But, if I had to do it again, I would go with microinverters, tiny inverters installed on each individual panel which convert the DC electricity generated by the panels to the AC electricity our grid needs. I might possibly go with a central inverter system with Tigo Module Maximizers. These module maximizers essentially mimic microinverters, ensuring that the stupidest thing about a central inverter system – and it IS stupid – doesn’t happen: Namely, that an entire “string” of panels is brought down to the level of the lowest producing panel on that string due to some sort of electrical mathematical equation issue I’ve never bothered to investigate and, frankly, about which I don’t have much interest in
    micro-inverter

    An Enphase Energy microinverter.

    learning about. Why would we go with a microinverter system or Tigo Module Maximizer system instead of a plain old string-inverter system if we had to do it again? First, I’m 100-percent certain we would have made several hundred more kWh this year. How can I be so sure? One, because studies show microinverter-based systems outperform central inverter based systems. Two, because – and I don’t think solar installation companies talk enough to customers about this – snow is a huge shading issue for many homeowners. (I write more about snow below). The second reason I would go with a microinverter system if we had to do it again is because Enphase has announced a 25-year warranty on its microinverters. If they do indeed last 25 years, I have to believe that Enphase’s microinverters will actually be cheaper in the long run than a central inverter based system which, sometime around year 15, is going to cost a homeowner several thousand dollars for an inverter replacement. Yes, microinverters cost more upfront -- seemingly somewhere between 10 and 50 cents per watt more, depending on which online source you believe -- but, in the long run, they’ll out-produce a central inverter and, I’m pretty sure, will end up costing you less. Plus, you can add solar panels to your system without having to worry about ridiculous “string” and central inverter issues.
  • Install an energy efficient roof, possibly even a metal roof, before installing solar. When we had our roof replaced in the summer of 2006, we had no idea we would go solar in 2010. If we had known we were going to go solar, I definitely would have looked into energy efficient roofing that reflects the sun/heat, including metal roofing, which has the added benefit of being recyclable. The high heat levels generated by our relatively dark asphalt shingles significantly reduce our solar system’s efficiency on hot days. And, on top of that, energy efficient/reflective roofing keeps the house cooler and saves on cooling costs. Wish I’d been more aware of these things in 2006!

  • snow-mattersSnow is a significant shading issue. I kept close track of production lost to snow and/or production we would have lost to snow if I hadn’t swept our lower string of 13 panels. In all, I estimate that we lost more than 100 kWh to snow because I couldn’t sweep our upper string of 13 panels due to safety issues. I estimate that we would have produced at least 250 kWh more if we’d been able to clear our entire 26-panel system free of snow immediately after a snowstorm. Our 19-degree roof pitch hurt us as snow just doesn’t slide off our panels: It takes days and days to melt, even in bright, blue sunny conditions. Meanwhile, because we have a central inverter system, we essentially get no production even if most of the panels on a string are entirely free of snow. This thanks to yes, I will say it again, the stupid, lowest common denominator limitations of a central inverter based system. If you live in a climate with lots of snowstorms frequently followed by sunny days and you have a low roof pitch, say anything 25 degrees or less, I would strongly recommend you invest the extra dough in a microinverter based system or in Tigo Module Maximizers when you have your system installed.

  • Leasing vs. buying. We signed the contract for our 5.59 kW system in late July 2009, about three months before residential solar leasing arrived in Colorado (leasing is now available in 12 U.S. states). Back then, I had a feeling leasing was coming to Colorado relatively soon, but the solar consultant who sold us our system convinced me we were at least a year away from that – and I didn’t want to wait that long to go solar. If we’d known, back in July 2009, that leasing was just three months away in Colorado, we probably would’ve waited and leased. We didn’t have the $11,500 to plunk down in cash. In fact, we didn’t get solar installed until ten months after we signed the contract so that we could save that cash. In the end, I’m glad we bought instead of leased. I like the idea that we own the system and that every single kWh we produce is ours. We also got a fantastic deal: $3.40 per watt utility rebate + 30 percent federal tax credit + $500 City of Aurora rebate, which brought a $31,000 5.59 kW system down to $8,000 in out-of-pocket costs. Almost two years after we signed our contract, I have yet to hear of a single residential homeowner anywhere in the U.S. who has paid less, out of pocket, for a professionally installed solar system than we have! Of course, if we hadn’t gotten such a great deal – and too many people even today cannot get the deal we did two years ago – I might feel differently about buying being better than leasing in our case.

  • solar-charged-savingsWill we ever catch up on our banked kWH? Silly me, back in late 2009 I thought production EVs would be here in Colorado by Fall 2011. That’s certainly at least the indirect impression Nissan gave me, and thousands of others in heartland America, when it had us reserve LEAFs in April 2010. Now, it’s looking like we might not see any LEAFs until 2013! It’s possible Ford might get a Focus EV to Denver by late 2011 – Denver’s one of 20 U.S. rollout markets for the Focus Electric. It’s also possible we won’t see production EVs in Colorado until 2013. If that’s the case, we’ll have up to 15,000 kWh banked with our utility, Xcel Energy. That’s about 50,000 miles of driving in an EV by spring 2013. And, of course, we’ll still be producing about 8,500 solar kWh a year. Basically, we’re going to need two plug-in cars to start to chip away at our banked kWh. Two plug-ins, one pure EV and one PHEV, is in fact our ideal, although admittedly expensive, goal. Even if we get there, I’m wondering if we’ll always be in the black in terms of our kWh. Who knows, we might need to replace our aging natural gas water heater with an on-demand electric water heater ;-)

  • Nothing beats the feeling of producing your own electricity. It’s way cool to know that on a sunny day – of which we have about 300 on Colorado’s nearly perfect-for-solar Front Range -- our solar system is powering our fridge, our computer, our television, our vacuum cleaner, our dishwasher, our electric range oven, a completely emissions free lawnmower, and, last, but certainly not least, our electric kitty litter box. Of course, it will be way cooler when we finally have an EV in our garage. Then, we’ll be tanking up with solar, and saying goodbye to Big Oil. I can’t wait until we get to the point where we’re a one pure EV, one PHEV household and we're filling up on gasoline, most likely, no more than six to eight times a year. Take that Big Oil – and imagine not just a handful of people doing what we’re doing, but hundreds of thousands, and, eventually, millions and millions!
1-year-of-banked-kwh

Our digital meter started with all zeros on June 28, 2010 and it's run backward 5,148 kWh since. Of course, we don't have an EV yet,

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