Sunday, December 30, 2012

One Year With Solar Energy at Home: Mostly Sunny

Just over a year ago, Kevin Toefel covered the back roof of his house in southeastern Pennsylvania with 41 solar panels. After 12 months the system generated 13.8 megawatt hours of electricity while using only 7.59 megawatt hours. The energy surplus becomes a credit on his electric bill, and once per year the electric company issues a check for any unused credit....

They use CFL or LED bulbs throughout the house, and solar-powered chargers for mobile devices. (The most recent one is outstanding.) 
After coming into some money and conducting research on solar energy (this site helps estimate system sizing, pricing, and benefits—return on investment,...), the household decided to go with solar panels, moved in part because their rear roof faces south.
He requested a number of quotes for installation and the best was $5.50 per watt. They looked at their electricity usage for the prior year—they’re a family of four, with two full-time work-at-home people—and overspecified the system by 25 percent capacity.

The specified 9.43 kW (DC) system used 41 230 watt panels—which produced 12.05 megawatt hours of electricity from Nov. 1, 2011, to Oct. 31, 2012. It cost $51,865 up front, including installation, permits, inspections, parts, labor, and warranty.  The federal tax credit totaled $15,560.  Many states offer rebates on solar projects; Pennsylvania provided a check for around $7,100 once the system was up and running. The net cost then was $29,205.

... Companies in some states offer no-money-down solar panel systems: They install a system on your property and then you lease it. The company reaps the incentive benefits, but you may save money on your electricity bill.

He had thought the system would be complicated, but it was not. ... 

The system needs an inverter for AC power. They considered one single inverter but instead opted for individual microinverters attached to every panel. If one panel or inverter fails, it’s easier to locate and fix the issue. In addition, the microinverters feed real-time data from every panel via Ethernet ... to a small Web server included for monitoring purposes.... The microinverters, and Web server ... are made by Enphase. 

Because of the solar panels, two additional electrical meters were needed. They still have the original meter that measures electricity use from the grid, but they also needed a new meter to measure power output, and a third to measure the difference between electricity created and used. ... In this graph below—from Enlighten’s Web service that creates reports—you can see exactly how much energy they produced on a daily basis.

The graph gives a rough history of the weather where they live. The drops on the graph represent days with little or no sun, although even on a cloudy day they make a little energy. Here’s a look at the numbers for production and usage by month:

There’s no maintenance to the system....

One of the upfront decisions you’ll need to make when planning a solar panel system is, will you still be tied to the electric grid which costs less up front.  The off-grid system provides stored power during the evening hours or during an outage. Their on grid system means all the power the panels create is actually fed back into the grid; they still get all their power from the electric company. And in the case of an outage, grid-tie systems are automatically disabled, because it would be unsafe for the workers trying to fix the outage.  To go completely off grid and have batteries store excess power would have added approximately 20 percent to up-front costs. 
The biggest issue for most is likely the large up-front costs involved, although you could start small and build up the system over time.... The payback period—which will vary based on the system, location, and energy costs without solar—can be high. Their break-even point is around 7.3 years, but that includes the home appreciation expected due to the system.

They already gained an appreciation benefit from the panels. Taking advantage of the low rates, they refinanced their home last month, and the added value of the solar panels was around $30,000. They were paying around $2,500 per year for electricity before the system was built; now they build up a credit most months. Any price increase means they will get more for their excess energy production.

By Kevin C. Tofel
Posted on GigaOM; November 12, 2012

No comments:

Post a Comment