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Solar Power in the Northern Neck

If you want to install solar panels, two interrelated questions must be answered:

  1. How much power do you want to produce?

  2. Will the panels be mounted on a roof or will they be ground-mounted?

The best azimuth for the array is slightly west of south, say 200º, and the best angle is about 34º. Full sunlight generates the most power so shade must be minimized. An average panel is about 65 x 39 inches and can be installed either horizontally (landscape) or vertically (portrait). Single panels are typically rated at about 300 watts, but only about 85% of the rated power will be realized largely because of inefficiencies in converting DC to AC. A “lockable, load-breaking manual disconnect switch” must be installed near the meter.

The Virginia Administrative Code (§ 56-594) states that generating facilities “shall not exceed the expected annual energy consumption based on the previous 12 months of billing history,“ and cannot exceed 20 kilowatts. As a place to start, determine your annual usage from your electric bill. Then figure out how many panels you want and where they will go. A zoning permit and an electrical permit from the county are required. Also required, from the power company, is a form certifying Liability Insurance (20VAC5-315-60) and form NMIN (20VAC5-315-30) giving notice of your intent to operate a generating facility.

A contractor should be identified to do the electrical (or all) work. NAPS has a list of contractors and you will likely profit from discussions with folks who have installed working systems. In 2019 a tax credit of 30% of the total cost applies, which can be spread over several years (IRS form 5695). The credit drops to 26% in 2020, 22% in 2021 and zero thereafter, unless changed by Congress or a new administration.

It is often stated that the cost of an average installation is between about $11,000 and $15,000 after the 30% 2019 solar tax credit. We were at the low end of this range because I built the frame and installed the raceway (conduit) in the trench. It is unlikely that the reduced cost of power will offset our cost of installation in less than a decade.

It is preferable to use micro-inverters that convert direct current (DC) produced by each solar panel to alternating current (AC). Differences in production by different panels are better smoothed out and you can track the performance of each panel via the internet. A single inverter has a warranty considerably shorter (for good reason!) than either the panels or micro-inverters (each typically 25 years). Battery storage raises the cost considerably at current prices, but allows solar power to be used at night. It can be added later. Power outages are typically short, and a very long outage would drain the batteries. Isolation switches must be installed if solar power is to be used during a power outage so that activating the grid and injuring a lineman is prevented. Solar Renewable Energy Certificates (SRECS) are unlikely to be worthwhile for small generating facilities in Virginia at this time.

Our 5.25 kW ground-mounted array (15 Hyundai 350 watt panels and Enphase micro-inverters) produces 4.4 kW peak AC power. “Net metering” credits us with the power we produce at the same price as the power we purchase. It will be at least a year before the economics are quantified. Because of trees at the horizons, our ground-mounted array generates more than half power (200 kW) for only about 5 hours each day instead of about 8 hours for a completely unshaded array. The array has nearly halved our NNEC electric bills.

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