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Your Solar Guide: Solar Panel Performance Terminology

The quality of solar panels determines the efficiency and performance of your system. Not all company’s install high-quality panels on your project. Solar Chief is committed to equipping its customers with the most reliable and efficient solar panels. To learn more about Solar Chief and contact us today!

Solar Panel Performance Terminology

Solar Efficiency Terms

AMPM standard: rating indicates how solar panels perform from peak sunlight hours to nonpeak sunlight hours. Indicates how a panel will perform and takes into account light variations during the day, ambient temperatures and factors related to air mass that affect solar energy potential.

Normal operating cell temperature (NOCT) rating: rating of a solar power system’s potential to withstand factors that affect efficiency. The calculation uses peak sunshine during the assessment.

Peak watt rating: this number reflects testing in laboratory conditions and shows how much energy in peak watts (Wp) a solar module generates.

Solar Energy Performance Terms

Current at maximum power (Im): rates the solar panel’s production of electricity after inverting solar power into DC power.

Current-voltage (IV): ratings compare the differences in terms of output when insolation (the amount of light that falls on a panel) and temperature vary. This rating is useful for learning how a solar panel will perform as the temperature changes and sunlight potential decreases on a cloudy day.

Nominal voltage (Vn): shows the voltage compatible with the solar panels. This often ranges from six to 24 volts, but it can be 48 volts or even more.

Rated power: shows the solar panel’s ability to sustain power output throughout the day, defines the panel’s peak capacity.

Temperature at rated power: is a standard that manufacturers use to rate solar panels’ performance at a specific temperature.

Voltage at peak power (Vp): the panel’s maximum voltage output when it’s producing electricity at its highest rate.

Ask the Experts: Can Solar Panels Harm Your Roof?

Many people interested in solar panels are concerned with the impact it will have on their roof. I took this question to our lead installer Trip.

About Trip: Trip is our reputable and skilled lead solar array installer. Trip is a straightforward guy that is trusted by the members of our community. He prides himself on educating the buyer on everything solar. Trip takes a personal approach with the customer even gives out his personal cell phone number in case they have any questions or concerns.

Can solar panels damage your roof?

Trip: Not if they are installed correctly.

The racking system joins the solar panels to your roof. A hole must be created in the rafter to secure the racking system. To prevent water from getting through the new hole, the bolt will be surrounded by flashing, which is a metal or plastic shield that fits under existing roof tiles. This flashing is additionally sealed with tar or comparable material. The lag bolt hole is also filled with a sealant to protect against water drainage in your roof.

Solar panels actually serve as a barrier to protect your roof from sun, rain, snow, and hail. The panels are made to withstand exposure to various weather conditions.

In addition to providing a barrier from harmful weather, rooftop solar arrays allow air flow between the roof and the solar panels, which increases airflow and adds a cooling effect of the solar array. In turn, the cooling helps the efficiency of solar panels.

Rooftop solar can turn your roof from a liability to an asset. Your rooftop goes unused without solar. Rooftop solar can produce your own energy with the option to net meter unused energy.

Going Solar: Solar Sheep

A ground-mounted solar array is a great option when going solar, especially when a roof does not provide enough space for an efficient solar array. The disadvantage of the ground-mounted solar array is the landscape maintenance around the system. The grass could get too high and cast shade on the panels, which will reduce energy production. Luckily there is a great eco-friendly solution to this problem… Solar Sheep. Below are the benefits of investing in sheep to maintain your ground-mounted solar array. Source: Nicole Duimstra

1. Solar sheep reduce operation and maintenance costs

At the Carilion New River Valley Medical Center near Roanoke, Virginia, the site of the 1.3 megawatt ground-mounted solar array installed by Secure Futures in 2017, takes about two days to mow with mechanical equipment and costs about $3,000 a pop. That’s no sheep date! Multiply this by a few times a year and the cost really starts to add up. Maybe we’re sheep-skates, but we would rather cut out the cost of mechanical mowing and pass along the savings to our customers.

Carilion NRV solar array
The 1.3 megawatt ground-mounted solar power system at Carilion New River Valley Medical Center.

2. Sheep drastically lower the need for mowing and herbicides

Of course, there are many options to maintain grassy fields. Mowing and the use of herbicides are the traditional choice to keep weeds at bay – although the use of gas-powered mowers and toxic herbicides seem counterintuitive for a solar farm, which should boast a low environmental footprint. By contrast, sheep can organically maintain a majority of the fields with much lower emissions from fossil fuels while trimmers and herbicides are only used to clean up what the sheep won’t eat.

3. Other livestock don’t compare to sheep

Don’t let other cute farm animals pull the wool over your eyes. Other livestock have been used to maintain solar farms, but without much success.

Cows and horses, like mowers, are so tall that their bodies cast shade on solar panels while they’re grazing. Bigger animals also can bump into solar panels and racking, causing damage. Goats, as you’d expect, do a great job of grazing not just the field but the solar equipment too. Apparently, goats enjoy chomping on electrical wiring as much they enjoy chewing on grass.

Solar sheep are the answer. They are low cost, quietly do the job, and look cute doing it too.

4. Solar sheep provide opportunities for partner-sheeps with local farmers

Solar farms are actually providing a new market for farmers across the Ewe-nited States. Partnerships between solar farms and, well, plain old farms are becoming increasingly popular. For example, in North Carolina, a state known for many large solar arrays in rural areas, sheep farming has jumped from 21,000 to 30,000 livestock in just a decade. Sun-Raised Farms alone provide 4,000 sheep for their partnerships with solar developers at 28 separate solar farms.

Shepherds lend their sheep to graze as they would at a normal pasture without fear of overgrazing farm land, and the sheep can be sold at a profit at the end of the grazing season. Solar sheep boost the agricultural industry and promote an even lower-cost source of clean energy.

At Carilion’s New River Valley location, Secure Futures is partnering with local Pulaski County, VA shepherd Cecil King. In a barter agreement, Secure Futures will prepare the site for sheep and provide Cecil with free pasture for his flock and he will cut the grass and weeds at no cost. This partnership is an agreement promoting both renewable energy and local agriculture. I think the folks on Wool Street would call this a win-win-win situation.

5. Sheep maintain pasture, rather than paving over paradise

Of course, you can avoid mowing altogether if you pave over a site before you install a ground-mounted solar array. Asphalt or concrete will certainly keep weeds, and any other living things for that matter, at bay. But paving creates its own problems for a ground-mounted solar array – it increases both stormwater runoff and excess heat that damages solar panels. By contrast, sheep can maintain pasture and restore otherwise depleted soil by natural means (yup, you know what I’m saying).

By maintaining a pasture, sheep also support native vegetation and pollinators.  With less mowing, herbicides, or pavement, solar farms can be retrofitted with native vegetation. While solar sheep maintain local vegetation, pollinators like butterflies and bees can flourish in an environment with little noise or chemicals.

6. Solar panels maintain sheep health and shepherds’ well-being

Solar panels benefit sheep and farmers by providing shade. Livestock are susceptible to heat stress from sun exposure. A sheep’s thick wool usually serves as great insulation from the sun, but sometimes this isn’t enough to save them from the Virginia heat.

Heat stress can cause or worsen several health problems in sheep, such as weight loss, reduced milk production and quality, shorter pregnancies and underweight births, compromised immune systems, and reduced male fertility. The effects of heat stress are passed onto a farmer’s well-being, where a flock’s health is particularly significant in terms of profit.

Carilion’s solar panels are in “table-top” position, providing plenty of shade for grazing sheep

Although the effects of heat stress are serious, the fix is relatively easy.  A simple shade shelter, like hanging tarps or cloth, significantly reduces the likelihood of heat stress.

Mounted a few feet off the ground, solar panels provide the sheep excellent shade from the heat while they graze underneath. As an extra bonus, the Carilion solar array has a tracking system, which means the solar panels follow the sun during the day to maximize production. So, at the hottest time of the day, the panels are at “tabletop” position – providing great sun cover for sheep.

Solar shade will maintain sheep health by reducing the risk of heat stress, and shepherds will benefit from healthy solar sheep with a higher market value of their flock.

7. They’re living their best lives

What do sheep do? They bleep and they graze. Really, that’s it. The best part about solar sheep is that allowing them to simply exist on site is the most cost-effective, sustainable way to maintain solar farms.

These sheep are living their best lives. At Carilion, they will be enclosed by a high fence to protect both the sheep from predators and the solar panels from outside disturbances. After all, we don’t want any pesky deer eating our solar panel wiring.

8. You can peep the sheep at Carilion

This year, Carilion will host 30 sheep during the month of September. While everyone involved is excited to practice sustainability, promote renewable energy, support local farmers, and reduce cost for the medical center, livestock can be unpredictable.  This September will serve as a learning experience for Secure Futures in how to best manage the solar sheep. If all goes well at Carilion, we will hopefully see more solar sheep at our sites.

Solar Development on Public Lands

The debate over developing solar energy projects on public land has proven to be a controversial topic. The article below describes the benefits of solar development on public land.


Solar development on public lands offers many benefits, from reducing the threat of climate change to creating green jobs. Large-scale projects can have serious impacts on the land, so it is important that they are built in the right places and the right ways.

By focusing on development in smart places and off-setting or mitigating the impacts, we can:

  • Protect wildlands and sensitive wildlife habitat.
  • Facilitate responsible development by taking advantage of nearby existing roads and power lines. This makes development faster, cheaper and better for the environment, solar developers and consumers.
  • Restore and repair damaged wildlands and wildlife habitats in areas where renewable energy development is occurring.

The Wilderness Society continues to work in collaboration with:

  • Conservation partners at regional and national organizations. 
  • Solar developers. 
  • Government agencies, including the BLM and Department of Energy. 
  • Utilities that manage the power grid and deliver power to consumers.