Heat Pump La Mirada California

John Bloom's solar-electric system produces more than a third of his family's summer electricity needs and almost two-thirds of their needs the rest of the year.

If you weren't living in California during the summer of 2000, you might not appreciate all of the reasons that prompted me to install a photovoltaic (PV) system the following winter. The state's poor deregulation policies allowed unforeseen price gouging, as regional energy suppliers created an artificial shortage to drive prices higher. It looked like affordable electricity was not something that our family could take for granted anymore.

Reliability was another problem. In addition to the threat of rolling blackouts (which our home never experienced, fortunately), our neighborhood lost electricity three times over two months due to auto accidents in which utility poles were struck. The specter of food thawing in the freezer (in summer) or a gradually chilling home (in winter) motivated me to look into backup electricity options.

The Dream

My initial interest in solar electricity focused on inverter/ charger units with battery backup so that we would have the ability to run off-grid. However, as I read one inverter's 150-page instruction manual and began to visualize several large cabinets in my garage full of lead-acid batteries that required monthly maintenance, it struck me that such a system would be a liability instead of an asset when we went to sell the house.

After all, we were not living in the remote desert off-grid, or where frequent utility outages were the norm, but in suburban Los Angeles. So we bought a 4-kilowatt portable gas generator to have on hand for emergencies, but still, the PV dream didn't fade.

OK, I'll admit it—I think photovoltaics are "cool." The ability to harvest electrical energy directly from the sun is as exciting to me as the World Series may be to others. But I get to watch my game every day!


Several factors combined to push this dream into reality.

Net metering. Most of the electricity I produce is credited against the highest-cost tier of energy I actually buy, so we reduce our energy costs by 15 to 20 cents per KWH generated.

Ease of use. Grid-tie inverters, unlike inverter/charger units, have no user controls, so there is much less technology to fear, or to scare future home buyers away.

Low maintenance. Hosing off the panels every now and then is no more difficult than washing the car.

Financial incentives. Two California state rebates—a US$3 per watt reimbursement, plus a state income tax credit, underwrote half the cost of the system.

Stewardship. If I can make better use of the sunlight that falls on my roof, and encourage others to do the same, then I'm helping manage the energy resources that God gave us.

With these motivations, I began to explore possible system configurations. I found the helpful Web site of Northern Arizona Wind and Sun (NAW&S). It provided a lot of background information, in addition to offering one-stop shopping.

Given the layout of our house, the best roof area is the southern side over our garage. It is clear of vent pipes and the underside is easy to access for installing roof supports. However, it is less than 300 square feet (28m2) of area and in plain view from the street, although the grade of the

The new and improved Sun Tie inverter is as quiet and maintenance-free as any appliance in the house.

The new and improved Sun Tie inverter is as quiet and maintenance-free as any appliance in the house.

Tech Specs

System type: Batteryless, grid-tie PV system System location: La Mirada, California Solar resource: 5.5 average daily peak sun hours Production: 200 to 400 AC KWH per month Utility electricity offset: 33 percent (summer), 66 percent (rest of year)


Modules: 24 Kyocera KC120-1, 120 W STC, 12 VDC

Array: Six, four-module series strings, 2,880 W STC total, 48 VDC

Array combiner box: Built-in Xantrex Sun Tie with 20 A fuses

Array disconnect: Built-in Xantrex Sun Tie, 100 A breaker and 1 A GFI

Array installation: Mounts from Northern Arizona Wind & Sun placed on south-facing roof, 13-degree tilt

Balance of System

Inverter: Initially Xantrex Sun Tie ST2500, now ST2500 XR-UPG, 48 VDC input, 240 VAC output, 120 VDC maximum DC input voltage, 44-85 VDC MPPT voltage window

System performance metering: Xantrex XR remote, Solar Guppy PC software, data logger and solar irradiance sensor (provided by Xantrex for beta testing)

front yard helps to screen it. Thus my panel options were limited by the need for high efficiency in a small area, and aesthetics. Kyocera won the aesthetics factor because its cells are square, and the panels are almost solid blue instead of blue dots on a white background.

Going with a Sun Tie inverter from Xantrex seemed like a good idea to me because the company had a good family of products, and I had received very good information and help over the phone from their tech support staff.


The installation went smoothly and I did almost all of it myself. Since our main breaker panel was at the opposite corner of the house, I installed a 60-amp branch panel in the garage to connect the inverter to, and to provide additional circuits for the kitchen and bath remodeling that I was doing. Along with the PV panels and inverter, I ordered mounting rail kits from NAW&S, which simplified the installation.

Sun Tie Inverter Performance Tests

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