Initial cost



Oregon tax credit


Federal tax credit


Energy Trust of Oregon rebate


Total Incentives


Total Cost


Configuring the System

The array is comprised of three, 11-module strings, feeding a single SMA America Sunny Boy 6,000 W inverter. The SB 6000US features a handy and time-saving extra—a built-in, four-pole disconnect, so both the AC and DC can be turned off with one switch. As required by Energy Trust of Oregon, we installed a Centron permanent KWH meter to keep an uninterrupted record of the system's AC output in the event that the inverter might have to be serviced.

Before installing the system, we hired an engineer to make sure the steel awning on the front of the building would support a half-ton of additional module and racking weight. Once we received the thumbs up, we got to work, mounting groups of three modules together on the ground, which allowed us to precisely set two parallel underside rails to match the modules' bolt-hole pattern. Because someone had recently stolen modules from a similar awning mount system on a nearby building, we riveted cover plates over the bolts as a theft deterrent.

Using a boom lift, we raised each three-module group and positioned it on the frame. Four assistants put up the whole PV array in a day. We had already installed the inverter, had an electrician do the AC wiring, and ran conduit while waiting for the engineering report. It just took one more day to complete the DC wire run and then the system was ready to go.

Throwing the Switch

On August 25, 2007, the day after we finished installing the system, we hosted a "Throwing the Switch" open house to celebrate. Representatives from Pacific Power came to install

Tech Specs


System type: Batteryless, grid-tie solar-electric Location: Portland, Oregon

Solar resource: 3.9 average daily peak sun-hours Average monthly production: 694 AC KWH Utility electricity offset annually: 100%


Modules: 33, Sharp ND-208U1F, 208 W STC, 28.7 Vmp

Array: Three, 11-module series strings, 2,288 W STC each, 6.86 KW total, 315.7 Vmp

Array installation: Custom 1.5 in. aluminum square tube mounts installed on south-facing awning, 15-degree tilt

Inverter: SMA SB 6000US, with integrated 15 A fused combiner and AC/DC disconnect, 6 KW rated output, 600 VDC maximum input, 250-480 VDC MPPT operating range, 240 VAC output

System performance metering: Centron Itron KWH meter the net meter and brought along a photographer to cover the story for their company's newsletter. Our project was apparently big news, as it had established the first "truly" net zero-energy commercial facility in the company's six-state service district.

Even as a solar installer who has personally completed almost 2,000 solar projects, I still get a thrill when flipping the switch for the first time. Ironically, the big moment was delayed by a local power outage caused by a car accident that had damaged a transformer. But we didn't let an outage slow down the party. We quickly rigged a battery-based portable PV system to provide electricity for lighting and music, including the ever-so-appropriate Beatles' classic, "Here Comes the Sun." We roasted hot dogs and baked cookies in solar cookers.

Unfortunately, when we did finally flip the switch later that day after power had been restored, we discovered a

Paying for the System

Professionally installed PV systems in our area run about $10 per peak watt. For the system I sized for our net zero-energy building, I was looking at an investment of almost $68,000. My first thought was, "Yikes! Where am I going to get that kind of money?"

I considered the possibility of finding a third-party investor, who would buy the system, take the tax credits, utility incentives, and depreciation, and then lease the equipment to our business. In turn, we'd pay rent on the system for a cost roughly equal to the projected energy savings. However, since this option is generally used with larger systems, I had trouble finding a third party interested in our relatively small project. I did eventually have one taker, but in the end, the buy-out provision of the lease asked for "fair market value," which could have been $50,000 or more with appreciation—more than I was willing to pay. I didn't want to end up paying for the system twice.

Instead, I found unsecured private financing at 7%. A low-interest loan through the state of Oregon's Solar Energy Loan Program would have come with a slightly more competitive rate, but the terms required that I take out a second mortgage on the building—which didn't appeal to me. Though I was not wild about taking on such a large loan, the numbers were less daunting once I factored in all the tax credits and incentives: an $8,580 rebate from the Energy Trust of Oregon; a $11,670 federal tax refund (30% of the system's cost, less the Energy Trust of Oregon incentive); and a $27,000 state tax credit taken over five years.

In the first six months of the loan, I recovered about half of the loan amount. By the time all the credits come in, I will have covered nearly 80%. With all the incentives, the actual tax reduction from depreciation, and the value at current electric rates of the energy saved by the system, I estimate full payback in seven years. It was that easy. With just a few pushes of the pencil, I went from "Yikes!" to "Done deal!"

Phantom Protection

Any net zero-energy home or business must zealously guard against phantom loads—energy that is gobbled up even when equipment is turned "off." To slay these energy wasters, we plug our photocopy/fax machine and every computer into power strips that are switched off every night. All devices with wall cubes are also plugged into power strips. We even went so far as to do away with a doorbell, and selected a microwave that does not have an LED clock. The building is as phantom-proof as we know how to make it.

An exception—over coffee—was almost made when office java drinkers organized and requested an automatic coffee maker. Brewing coffee and keeping it hot all day was not something I was excited about, especially since I'm not a coffee drinker. But we compromised—I allowed the coffee maker, but only on the grounds that it is turned off immediately after coffee is brewed, and the coffee is transferred into an insulated dispenser that keeps it warm all day.

technical problem—the SMA inverter kept blowing fuses. We got the company's technical support on the phone and worked through the possible scenarios. Based on their suggestion, we decided to rewire and bring the three individual strings into the inverter rather than combining them at the array.

A week later, with the rewiring complete, we gave it another go on a gorgeous, sunny day. The system cranked out 31 AC KWH on that first day. And the best part: Our new Pacific Power bidirectional meter read zero when it was first installed, and the first number recorded was -1. There was nothing like watching the meter spin backward, knowing that we were well on our way to net zero-energy use.


John Patterson ([email protected]) is president of Mr. Sun Solar and inventor of the Sol-Reliant solar water heating system. Over the past 28 years, his company has installed more than 1,900 solar energy systems, including solar hot water, solar pool heating, and photovoltaic systems.

Suzanne Olsen ([email protected]) is a writer and photographer specializing in renewable energy and the environment.

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Velux Sun Tunnel • PV System Components:

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