Project Description

Solar Panels in Winter – Do They Work in Snow?

The exponential growth of solar power in the U.S. is easy to understand in light of the major cost-saving benefits of this environmentally friendly energy resource. And the fact that the cost of installing solar panels has decreased by nearly 70% over the past decade makes solar the most attractive renewable energy option around. But when people think of energy from the sun, many who live in areas that have cold, snowy winters wonder if solar is viable for them. And it’s a good question to ask: do solar panels work in the winters of snow regions?

Solar Panels’ Efficiency in Winter:

While there are fewer hours of daylight and more overcast days during winter months in many parts of the country, solar photovoltaic (PV) energy systems are still absolutely feasible in cold-winter locales. In fact, according to the Solar Energy Industries Association (SEIA), New York, Massachusetts and New Jersey are among the top 10 states for solar implementation.

• Snow Enhances PV Production: How much power do solar panels produce in winter compared with other seasons? Of course, reduced electrical generation is inevitable with the season’s shorter periods of sunlight. Compensating for this somewhat, however, is the fact that as long as snow is not covering solar panels, its added light reflectivity can actually improve photovoltaic production. Also, like all electrical equipment, solar panels operate more efficiently in colder temperatures.
• Snow Removal from Solar Panels: While it is true that solar panels covered with snow cannot generate PV energy, this situation realistically only occurs about three months out of the year in the snowier regions of the country. And because most panels are positioned at an angle, snow easily slides or melts off them under the right conditions. Dark-colored solar panels are designed to absorb light and heat energy, facilitating snow melt. In general, solar panels are 20°C (36°F) warmer than ambient temperature, and of course, this facilitates quicker melting of snow from them.

A positive effect of snow accumulating on solar panels is that when it melts, it has an anti-soiling effect (i.e., when melted snow drips off the panels as water, some of the efficiency-lowering accumulated dirt on the panels is also washed away with it).

If snow remains on the panels, however, there are special extendable solar panel roof rakes available to easily clear it away. Most solar installers take regional climate into consideration when designing a residential system. For areas known to get lots of snow in winter, mounting solar panels close to the ground is preferable for ease of access.

• Pole Mounts: Another option for residences in snowy locales is to mount solar panels on a pole, which increases their distance from the ground and thereby lowers the risk they will be buried in a heavy snowfall. In addition, since pole-mounted solar arrays tend to be positioned at a steeper angle, snow slides off of them more easily because of gravity. Another huge advantage of pole mounts is that the panels can be adjusted for maximum exposure to the sun, depending on the season. The sun’s path through the sky is lower during the winter, but the angle of the panels can be shifted accordingly with pole mounts.

• Effect of Net Metering: Most U.S. homeowners can participate in net metering, a significant incentive for maximizing the economic advantages of solar power. When days are long and sunny, as in the summer months, excess solar panel energy production can be effectively “stored” on a power company grid for later use.

Excess energy production (i.e., electricity produced above and beyond the amount being utilized by the residence) goes to the utility grid and is quantified by the power company as credits. Credits can be subsequently withdrawn as energy when needed or during the colder months, at which time shorter days and cloudier skies decrease solar panel electricity production. Basically, net metering is a free energy storage solution that ensures both consistent, adequate power supply and maximum cost-effectiveness to the consumer.

It should also be noted that the greater any location’s distance from the equator, the longer its summer days are. For more northerly states in the U.S., which tend to get snow in the winter, this effect enhances the amount of electricity produced during the summer months, and excess energy generated at this time can be transferred to the power grid for use in the colder seasons.

Solar Power Off the Grid:

For people living off the grid and not tied to a regional power company, more equipment is needed to ensure that home energy needs are consistently met. In this type of solar setup, electricity generated by solar panels must run through a charge controller to a battery pack. The controller regulates the amount of charge entering the batteries to preventing overcharging.

Battery packs store the power from an independent solar setup prior to AC conversion via an inverter. Reliable, deep cycle batteries such as the AIMS Lithium Battery 12V 200Ah LiFePO4 or the 12 Volt 200 Amps AGM Deep Cycle Maintenance Free Battery Heavy Duty, can be sensitive to temperature and should therefore be installed indoors. Although the batteries are manufacturer-warranted for several years, diagnostic equipment such as a digital multimeter and handheld battery refractometer should be kept on-hand to regularly monitor battery capability.

Electrical current runs from the battery bank to an off-grid inverter, which converts it to AC for use with various home appliances. An advantage of the off-grid setup is that the inverter does not have to match phase with a utility sine wave, as grid-tie inverters must. However, it is critical that a DC disconnect switch (fuse) be installed between the solar panels and controller, so that the system can be switched off for maintenance, troubleshooting or in a power overload.

How does the DC disconnect switch work? As current passes through the inverter cable for your solar-powered system, heat is generated. If the inverter draws more current than the cable can handle due to heavy loads, then excessive heat is produced. The fuse can handle a certain amount of excess current, but it’s designed to blow when the safe limits are exceeded and protect the inverter cable and battery from meltdown or fire damage.

Because off-grid systems cannot rely on a utility grid to supply them during photovoltaic shortages that can occur in short-day, overcast winter conditions, an extra generator should be kept on-hand to ensure continuity of power. A number of California Air Resources Board/Environmental Protection Agency (CARB/EPA) compliant inverter generator models from AIMS are available at The Inverter Store.

While it is more complex to run an off-grid solar setup, it can be empowering to be energy independent and unaffected by outages affecting the grid. Whether tied to a utility grid or not, however, solar panels’ efficiency in winter can be leveraged for overall adaptability to the changing seasons, yielding solid environmental benefits and energy cost savings.