What should I prioritize, efficiency or solar?

If you are interested in solar, you have probably also thought about improving the energy efficiency of your home or business. Hopefully you have already addressed the low hanging fruit, such as replacing all your most-used incandescent light bulbs with compact fluorescents or LEDs. Once you’ve moved beyond the easy stuff, you face the question of how to prioritize continued improvements in building efficiency with investment in solar production.

The traditional advice goes like this: “First do everything you can on the efficiency front to reduce your energy consumption needs, then invest in solar to cover to remaining need.”

What is Net Metering?

How does Net Metering work?
Net metering allows the grid to be a giant battery for solar. When the sun shines, the electricity produced will be used to power your home, and your electric meter will not spin. When you produce more than you use, the excess electricity will flow back to the grid, and your meter spins backwards. When you do not produce enough solar electricity for your home, your meter spins forward as it always has. Learn more about net metering in Vermont here and here.

What is the “solar adder”?

Vermont state law requires that utilities provide at least a minimum level of value for solar net metering. The way the law is put into effect depends on the utility involved and its rate structure.

If your utility is Green Mountain Power, then the solar adder functions as bonus credit on your electric bill for each kWh of solar you produce. You receive the solar adder for the first 10 years of your solar array. Learn more about GMP’s program .

Can my bill get to zero?
Yes, all extra electricity produced is converted to a dollar value, and this can be used to offset all charges and get your electric bill to zero.

What happens with extra electricity?
If you produce more electricity than you use in a month, a credit for this electricity can be carried forward for 12 months. This will be used to offset extra usage in future months. For most houses in Vermont, this means that extra solar electricity generated in the summer can be used to offset electricity usage in the winter.

Where Can I Put a Backyard Solar Tracker?

How much space does a solar Tracker require?
A Solaflect solar Tracker will occupy a circle 20 feet in diameter.

How much daylight is needed at the site of the solar Tracker?
The benefit of a solar Tracker is greatest if there is good solar exposure to the East and West. In most of Vermont, the sun is never below 23 degrees above the horizon due south. Solaflect Energy will do a free site analysis upon request in VT or NH.

How far away can the solar Tracker be from my house?
The solar Tracker can be 200 feet away from the house with standard wiring. It can easily be further than 200 feet with upgraded wiring.

How does the electricity get to my house?
Wires are buried beneath the ground between the solar Tracker and your house.

Is My Home a Candidate for a Solar Tracker?

A Tracker makes sense if you have an open field or yard with decent solar exposure. Solaflect Energy will provide a free site analysis upon request (in VT and NH). The electricity savings are about $1,300 per year. If your average monthly electric bill is over $110, the savings will benefit you the most. You also need to pay at least $5,700 in federal income taxes to take full advantage of the tax credits available. This can be over several years, however.

Why Solar Energy Now?

Is Solar Affordable?
YES – With Solaflect’s revolutionary technology, you can get an “after-tax” rate of return exceeding 8% per year, equivalent to a taxable return (e.g. interest on a bank account or money market) of 9% to 15% per year, depending upon your tax bracket.

How does Solaflect make Solar Energy affordable?
By following the sun throughout the day, a Solaflect Solar Tracker provides 30% to 40% more electricity than the same number of PV modules mounted on the perfect south facing roof. Its modular construction provides additional savings with costs similar to roof top installations. The U.S. Department of Energy has recognized Solaflect’s innovative design, and has twice provided $1 million awards to Solaflect after nationally competitive reviewed competitions. These awards have all been invested in the engineering of the Solaflect Tracker.

Will Solar Energy be cheaper next year, and if so, should I wait?
Solar may be cheaper but the incentives will probably lessen. This is a great time to invest in solar energy.

Will the technology become obsolete?
Only if electricity becomes obsolete. Once a Solaflect Tracker is installed, the electricity it generates is very close to being free for 25 years.

How much more electricity will I use if I switch to an electric dryer or oven/stove?

Many people looking to go solar want to take full advantage of solar as a source of clean, low-cost energy. This includes “electrifying” their lives by switching from gas to electric clothes dryers or electric stoves and ovens.

Efficiency Vermont provides estimates for the amount of electricity used by different sorts of appliances. They estimate that electric clothes dryers and electric stoves each use approximately 900 kWh per year, in the typical home. For Green Mountain Power customers, as an example, that works out to about $11 more on the electric bill per month for each appliance.

These values are for standard appliances. Heat pump clothes dryers use about half the energy of standard electric dryers. As Joe Rice at Green Building Advisors points out, heat pump clothes dryers can save energy indirectly as well, because they do not vent warm air out of the house in wintertime. That means your heating system doesn’t have to make up for the lost heat.

For cooking, you have option of an induction stove instead of standard resistance electric version. According to Popular Mechanics, an induction stove uses 30% less energy than a standard electric stove. (Incidentally, they report that the induction stove uses a whopping 93% less energy than a gas stove!) Keep in mind that converting to an induction stove doesn’t mean using 30% less energy overall for cooking, since induction only works on the stovetop, not in the oven.

How much more electricity will I use if I drive an electric car?

Driving an electric vehicle is an efficient way to get around, both in terms of energy and money. DriveElectricVT estimates that the cost to drive an electric vehicle—either all-electric or a plug-in hybrid—is equivalent to driving a gasoline car if gas is running at about $1 per gallon. And the cost for electricity is a lot more stable over time than the cost of gasoline.

If you are thinking about driving on electricity now or in the relatively near future, you may wonder about covering your electric vehicle’s needs with solar. The average American driver drives 13,476 miles per year, according to the Federal Highway Administration. An electric vehicle uses around 1/3rd of a kWh to drive 1 mile. That means to drive the average distance of 13,476 miles in a year, the car will go through 4,463 kWh. This is roughly 2/3rds to 3/4ths of the electric output of one Solaflect PV Tracker in Vermont or New Hampshire, depending on the Tracker’s location.

How much more electricity will I use if I add a heat pump to my house?

If you are considering solar, the odds are good that you are also interested in being energy efficient in general. The most efficient way to heat a home is with a heat pump (aka “mini-split”), and the most efficient way to heat hot water is with a heat pump water heater.*

What exactly is a heat pump?

A heat pump is a mechanism that captures energy from one place, concentrates it, and delivers it as heat to another place. A window air-conditioner is a familiar type of heat pump, which captures energy from your indoor air and moves it to the outdoors. The result is a cooler indoor space and a (very slightly) warmer outdoors.

When people use the term “heat pump,” they are usually referring to a system that runs in the opposite direction: it captures energy from the outdoors and uses it to warm the indoors. “Cold-climate heat pumps” are versions specially designed to operate down to very low temperatures. Depending on the model, they can capture usable heat from the outdoors even when outdoor temperatures drop as low as -18°F.

Similarly, a heat pump water heater captures heat from the air in your basement and uses it to heat water for your shower and sinks.

The nature of the heat pump cycle means that heat pumps deliver useful heat far more efficiently than systems that generate new heat directly. This translates into energy savings and associated monetary savings.

If you start heating your home and/or water with heat pumps, this will reduce the amount of propane or heating oil you were using previously, while increasing the amount of electricity you are using. In almost all cases, what you spend on the electricity will be a good bit less than what you would be spending on fossil fuels. This is, of course, especially true if your electricity is generated with a PV Tracker.

So what will happen to your electrical usage if you go with heat pumps? According to Green Mountain Power, use of a cold climate heat pump of the following sizes will result in approximately the following change in electric usage and cost. Naturally, the exact electricity use will vary from home to home based on many factors.

Electric usage from a cold climate heat pump (Green Mountain Power)

Heat pump BTU ratingAvg. monthly bill increaseAvg. monthly kWh increaseAnnual bill increaseAnnual kWh increase
9,000$26163 kWh$3121,950 kWh
12,000$37231 kWh$4442,775 kWh
15,000$47294 kWh$5643,525 kWh
18,000$63394 kWh$7564,725 kWh

Source: Green Mountain Power presentation at Montshire Museum of Science, June 7, 2016.

As for a heat pump water heater, here’s what that looks like.

Electric usage from a heat pump water heater

# peopleGallons used per dayAverage electricity usage to heat waterCost @ GMP residential rates
119.5716 kWh/yr60 kWh/month$10 per month
235.81,315 kWh/yr110 kWh/month$18 per month
352.01,910 kWh/yr159 kWh/month$26 per month
468.22,505 kWh/yr209 kWh/month$34 per month
584.43,101 kWh/yr258 kWh/month$42 per month

Sources: Parker & Fairey, “Estimating Daily Domestic Hot-Water Use in North American Homes” ; 10 CFR 430, Table III.3 Medium-Usage Draw Patterns ; calculations based on energy guide label.

* True, a solar hot water system can be even more energy efficient, but I defer to Martin Holladay at Green Building Advisors that “solar thermal is dead.”

Can I mow under my Solar Tracker?

Yes, you can mow under your Tracker. Your working space under the Tracker will depend on the time of day and day of year. That’s because the panels are tilted to face directly at the sun, and as the sun travels the tilt of the panels changes. As a result, the amount of space underneath the lowest edge of the panels changes.

When the Tracker is in the vertical position before sunrise and after sunset, the bottom edge of the panels is approximately 4 ft above the ground. You could easily mow under that with a push mower, but you’d risk collision if you were using a riding mower.

Of course, most mowing occurs during the day. On the Spring and Autumn equinoxes (on or about March and September 20th), the Tracker is tilted enough that the clearance beneath the panels is 5 ft or more from about 10:15 am through 3:45 pm. By Summer Solstice, you’ve got 5 ft or more of clearance from about 8:30 am through 5:15 pm.

How does solar production vary over the year?

Aka, take a ride on the Solar Coaster!

The amount of electricity generated by a PV Tracker varies greatly from month to month. Days in December (in Vermont and New Hampshire) are much shorter than in June. In December, each day lasts only about 9 hours. In June, each day lasts more than 15¼ hours, 70 percent longer than December’s day length.

In addition, weather patterns change throughout the season. These are not as reliable as the length of day, but we do tend to have cloudier weather in December which exacerbates that month’s low production.

Putting those factors together, you’ll understand why the number of kWhs generated from a Tracker will be quite different at different times of year. The chart below shows the production from one of our customer’s Trackers over the years 2014 and 2015. A peak month’s production can be more than 4 times that of a minimal month, and seasonally summer is nearly twice as productive as winter.

Monthly solar production and net metering value from a Solaflect PV Tracker, 2014 - 2015.
Monthly solar production and net metering value from a Solaflect PV Tracker, 2014 – 2015.

Many customers build up credit with the utility during the summer and use this credit to help offset winter electric bills.

Does northern New England get enough sunlight for solar to make sense?

The grass is always greener on the other side, and the sun always shines brighter in retirement states. Even so, Vermont and New Hampshire have no trouble sustaining healthy yards and pastures, and we easily get enough sunshine for solar to be a sensible choice for energy production.

Consider this map of the solar resource, created by the National Renewable Energy Lab: Read more

How does solar affect property values and property taxes?

Many homeowners wonder what will happen to their home’s property value if they add solar. A number of studies have looked at this question. The largest and most thorough to date was conducted by the Lawrence Berkeley National Lab and published in January 2015. It looked at data from eight states over a fifteen year time period. On average, home values increased by $4 per watt of installed solar capacity. One Solaflect PV Tracker has 4 kW (4,000 watts) of capacity. See the report here.

Note that in Vermont, state law exempts solar equipment from being assessed for property taxation, so long as the solar array is smaller than 50 kW in size (that is, fewer than 13 Solaflect PV Trackers).

In New Hampshire, each town has the option to exempt solar from property taxation. Details regarding the towns that have adopted an exemption are available here. New Hampshire residents interested in solar should contact their local government to confirm the exact details for their town.

What are “Renewable Energy Certificates”?

Renewable Energy Certificates (RECs) are an accounting mechanism to make it possible to keep track of responsibility for bringing renewable energy to the grid. When one megawatt-hour (MWh) of electricity is generated from a renewable energy facility that is registered with the grid operator, a REC is issued to represent the renewable aspect of that energy.

Electricity on the grid is identical, whether it comes from a solar array or a coal-fired power plant. But we all know that energy from the sun has a different impact on the world than energy from burning coal. The REC represents that difference. It represents the reduction in soot, mercury, smog, acid rain, radiation, and carbon dioxide that we get from solar (or other renewable) energy as compared to traditional sources. Because we want a cleaner, healthier world, there is social value in the difference represented by the REC.

RECs also have an economic value. Most states have laws requiring electric utilities to include renewable energy in their supply to customers. Each law is unique, but in general a utility complies with the law by presenting the required number of RECs to the state regulatory agency. It might get these RECs by building its own new facilities powered by renewable resources, by purchasing renewable energy generated by an independent producer along with the associated RECs, or by purchasing RECs by themselves, separately from the energy.

When a utility purchases RECs, it is paying the added cost that it takes to bring clean energy to the grid. So it becomes responsible for the renewable aspect of that energy. It doesn’t matter that the utility might be in one state and the renewable energy facility in a neighboring state. The electrical grid crosses state lines, and energy flows across the borders all the time. So does pollution. For the most part, it doesn’t matter if the renewable energy is generated in the first state or the second—as long as it gets generated, it helps to replace dirty power generation in the process.

As an accounting mechanism, it is imperative that all participants keep accurate account of who has what so that there won’t be any double counting. If Mr. Jones has a solar array and sells the RECs that are associated with it to a utility, then only the utility has legitimate claim to the “solar” aspect of the energy produced. Mr. Jones has sold the solar’ness. As the accounting of all energy on the grid works, Mr. Jones takes on responsibility for what is called the “residual mix.” This is the energy in the total electrical supply on the grid that has not been attributed to other participants. On the New England grid, the residual mix consists of 60% fossil fuel and 37% nuclear power.

A renewable energy project that sells its RECs gives up all claims to the positive environmental attributes of renewable energy. The buyer of the RECs has paid the price required to assume responsibility for the renewable energy. Those who sell their RECs trade their renewable energy for "residual mix." In New England, the chart above shows the sources of energy in the residual mix.
A renewable energy project that sells its RECs gives up all claims to the positive environmental attributes of renewable energy. The buyer of the RECs has paid the price required to assume responsibility for the renewable energy. Those who sell their RECs trade their renewable energy for “residual mix.” In New England, the chart above shows the sources of energy in the residual mix.

This is a complicated system. Complicated systems are easy to abuse, because consumers will have a hard time knowing when they are buying what they meant to buy, and when they are not. For this reason, the Federal Trade Commission has published guidelines in the Code of Federal Regulations regarding RECs and their appropriate use in marketing:

If a marketer generates renewable electricity but sells renewable energy certificates for all of that electricity, it would be deceptive for the marketer to represent, directly or by implication, that it uses renewable energy.
— 16 CFR 260.15(d)

Vermont statues depend on strict adherence to proper accounting to enable the state’s renewable energy programs:

The party claiming ownership of the tradeable renewable energy credits has acquired the exclusive legal ownership of all, and not less than all, the environmental attributes associated with that unit of energy.
— 30 VSA 8002(22)(B)

The Vermont Law School Energy Clinic has published guidance on the issue for those who are interested in community solar.

When RECs are stripped (unbundled) from the energy being generated from the renewable source, the offtakers and owners of the generation source can no longer claim the environmental attributes of the energy being generated. That is, they cannot say they are producing green energy. [Someone using energy that has had its RECs sold off] is no more reducing their carbon footprint than if they had not constructed the solar array in the first place.
— “What It Means to Separate the RECs from the Solar Energy”

When the REC system is abused with deceptive marketing practices, the result is not only consumers who are fooled into buying residual mix when they intended to buy solar energy. Solar developers engaging in these practices note that, by selling the RECs, they get added money that helps fund their projects, and they claim that therefore the sale of RECs has helped increase the amount of solar energy in the grid.

In fact, their deceptive marketing results in less new solar being constructed overall, rather than more.

Imagine a solar array is constructed in Vermont, and the developer sells the RECs associated with it to a utility in Massachusetts. If the story ended there, then this would be how the REC system was meant to work: new solar has been added to the grid, and it is used to help the utility satisfy its legal requirement regarding clean energy.

But instead, the developer then markets the same facility to the public as a “community solar” project. Vermonters buy into the project thinking that they are “going solar,” even though all of the solar attributes were sold off long before they entered the picture. These are people who wanted to go solar both to benefit from the cost savings of net metering and to do the right thing for the environment. While they are getting the net metering savings they expected, without realizing it they are not doing anything positive for the environment.

In other words, there is double counting going on in the system. The utility has bought the RECs and has legal, legitimate claim to responsibility for the solar energy generated by the project. Meanwhile, the Vermont customers think they went solar. Both the utility and the Vermont customers believe they have gone solar from this single facility, but only the utility is correct.

If the developer honestly wanted to provide community solar, s/he would have retained all the environmental attributes and not sold any RECs. Then the Vermont customers would genuinely be going solar. Meantime, the utility would still need to meet its legal requirements for clean energy, so it would have to support the funding of an alternative project. That way, in order to provide enough solar to satisfy both the utility and the Vermont customers, two separate solar facilities would need to be constructed.

When solar developers follow the rules regarding truth-in-advertising, the system as a whole ends up developing more solar. When developers play loose with the rules, less solar is developed. If all of this were just about money, it would be a simple case of taking advantage of customers. But solar is about more than the money. It is also about the global warming crisis, about asthma and other respiratory diseases caused or exacerbated by energy pollution, about mercury poisoning in the fish we eat. When deceptive marketing slows down the development of desperately needed renewable energy projects, the harm goes far beyond shifting a few dollars from some consumers’ pockets to those of the developer.

Solaflect Energy exists because its founder and employees are devoted to the benefits of solar energy. We are in the business of solar energy, not residual mix. Our customers honest and truly go solar—and they save money in the process.

How large is a Tracker?

A Solaflect PV Tracker carries 16 solar panels. As a group, they cover an area of 20 feet wide by 12 feet high. The riser holds them up a few feet off the ground so that it won’t be a snow plow as it rotates in wintertime.

The space the Tracker takes up visually depends on the time of day and season. If it is vertical (for example before sunrise and after sunset) and facing directly at the viewer, it looks at its largest.


If it is tilted up toward the sun and/or rotated away from the viewer, it fills less visual space. At the minimum perspective, it comes close to disappearing into the background.


All in all, a Tracker takes up a similar amount of visual space as a mature apple tree. If you stand right next to it, it feels somewhat large. If you are 50 feet away or more, its scale is much smaller.

How do I compare a proposal from Solaflect with one from another solar installer?

The tradition in the solar industry is to compare system costs according to their “cost per watt” of capacity. “Capacity” is the ability of the solar panels to produce a certain amount of electricity when exposed to light. More specifically, it is a measure of how much electricity the panels will create when they are at a specific temperature and are exposed to light of a specific intensity. For example, a solar array rated at 4 kilowatts (kW) will produce 4 kW of direct current electricity under standardized conditions. The amount of electricity created by the panels will vary if the temperature or intensity of light change.

(Before going further, it may help to understand the difference between a kilowatt and a kilowatt-hour.)

If you are comparing one installer’s proposal to put solar on your roof against another installer’s proposal to put solar on your roof, then comparing cost-per-watt is perfectly reasonable, as long as both installers are going to use similar quality equipment.

However, the Solaflect PV Tracker is qualitatively different from usual fixed-mount solar arrays. The advantage of the Tracker is precisely that it uses its solar panel capacity more effectively than do fixed-mount arrays. In particular, the Tracker ensures that the panels receive more intensity of light, because it keeps the panels facing directly at the sun at all times. Meanwhile solar panels in a fixed orientation are receiving light from an indirect angle at virtually all times throughout the year. The light landing on them has less intensity.

As a result, solar panels with 4 kW of capacity in the Solaflect PV Tracker will deliver more energy—measured in kilowatt-hours—than the same solar panels in a fixed array. (See “How does the Solaflect PV Tracker make more energy?” parts 1, 2, and 3.)

And energy is what you want. Capacity is merely a means to the end of producing energy. Your electric bill is calculated on the basis of energy—of kWhs. If you want to reduce your electric bill with a solar array, you want the array that will give you the most energy, the most kWhs, at the best cost.

Nine times out of ten, the most cost-effective solar option for you is going to be the Solaflect PV Tracker.

When you want to compare a proposal from Solaflect with one from another installer, ignore cost-per-watt since that is an apples-to-oranges comparison. Instead, calculate the cost-per-kWh using the expected kWh production from the first year. Of course, any solar array will continue producing energy long past the first year. Limiting this mathematical exercise to the first year is just to make it easier and quicker to get an apples-to-apples comparison.

To do this, look at the proposals and find the cost for the solar array, then divide this number by the expected kWhs to be produced in the first year. Using this value, cost-per-kWh, you can then make fair comparisons between any set of solar proposals.

A real-life example.

We recently provided a proposal to a Vermont farmer for two Trackers. This farmer also received a proposal from another installer for an array that would go on the barn roof. The farmer has a gorgeous place, both as a farm and for solar access with almost no shade at all from trees, buildings or ridge lines.

Here are the numbers to compare the two proposals.

 SolaflectAlternative installer
1. System cost (after tax credit)$26,530$31,375
2. System capacity8,000 watts (8 kW)8,520 watts (8.52 kW)
3. Cost-per-watt (traditional measure): Row 1 divided by Row 2$3.32$3.68
4. Solaflect cost advantage on capacity basis9.8% less than the alternative
5. Expected energy delivered in 1st year12,582 kWhs8,470 kWhs
6. Solaflect energy production advantage48.5% more than the alternative
7. Cost-per-kWh (first year production only): Row 1 divided by Row 5
This is your apples-to-apples comparison.
8. Solaflect cost advantage on energy basis43.1% less than the alternative

The precise values in this example are the result of the particulars at the farm, but they are indicative of the sort of value Solaflect customers receive. If you are thinking of going solar (and you should be!), you should be thinking of going Solaflect.

Will I get backup power from my Tracker if the utility grid is down?

Solaflect installs standard grid-connected systems. You will not get power from it when the utility grid is down. This is a National Electric Code safety feature built into the inverters. The inverter senses if the grid is operating normally. The moment the grid goes down, the inverter stops solar power from flowing through it. This is to prevent power backflowing into the grid where it might harm line crews that are fixing the grid.

For those who would like a degree of solar backup power when the grid is down, we offer an upgrade option to the SolarEdge StorEdge inverter. This inverter is fully compatible with the Tesla Powerwall battery system. We do not currently offer the Powerwall batteries directly, however with the StorEdge upgrade your Tracker system will be ready to “plug and play” with the Tesla Powerwall.

What’s the difference between kW and kWh?

Let’s start with the terminology. A kilowatt (abbreviated as kW) is the same as 1,000 watts (or W). A kilowatt-hour (abbreviated as kWh) is the same as 1,000 watt-hours (or Wh).

A watt is a measure of the amount of power flowing at one moment in time. If a solar array has a capacity rating of 4 kW, then it is capable of putting out a flow of 4 kW of energy under the right conditions.

If that solar array produces at a rate of 4 kW for one hour of time, then it has created 4 kWh of energy.

Think of watts (or kW) as a car’s speed—its capacity to move at a certain rate—and watt-hours (or kWhs) as the distance the car travels. You might be in a car that is going wicked fast, but if it only drives for 5 minutes before running out of gas, then it won’t take you far.

In general, what you want from your car is its ability to get you to your destination even it it does so in a slow-and-steady-wins-the-race sort of way. For solar, your “destination” is the creation of enough kWhs of energy to cover the needs of your electrical appliances, which is how you reduce your electric bill. If you can get those kWhs with the purchase of fewer kW of capacity, you are getting the best value out of your investment.

By tracking the sun, the Solaflect PV Tracker generates the maximum possible number of kWhs of energy from the watts of solar panel capacity.

What’s happening with the Federal tax credit for solar?

The “Residential Renewable Energy Tax Credit” is a Federal income tax credit available worth 30% of the total cost of the solar array. This is available for solar installed for primary and secondary residences. For a Solaflect PV Tracker, this is worth nearly $6,000. In  December 2015, Congress extended the tax credit. It will be 30% through the end of 2019. After that the credit steps down over a few years. In the final year, 2021, the credit will be 22%.

Tax credits are different from tax deductions. To use a tax credit, you first calculate how much tax you owe for the year. Then, instead of paying that amount of tax, you apply the tax credit as “payment” instead. That means that the tax credit has full face value, unlike deductions.

If you have already paid taxes over the year through withholding, then applying the tax credit can translate into a larger refund. However, the solar tax credit is non-refundable. That means that if you owe less in Federal income taxes for the year than the size of the credit, you will not receive the difference as a refund. Instead, you can carry forward any unused portion of the tax credit to the next year’s taxes.

To claim the tax credit, use IRS form 5695. The Department of Energy also has information on the tax credit.

Please note that Solaflect cannot and does not give tax advice. To properly determine your use of any tax credit, you should consult with a tax professional who can review the specifics of your situation.

What happens to the Tracker when it is windy?

Solaflect PV Trackers include anemometers that are constantly measuring wind speed. If the wind speed gets high enough, the Tracker will “stow” in a horizontal orientation. By going flat, the Tracker presents only a thin edge to the wind, which can slide by easily.

Once the wind has calmed, the Tracker automatically returns to its normal orientation. While in the stowed position, the panels are facing upward. If this happens during daytime, they will still produce energy, even if not quite as much as when facing directly at the sun.

A Solaflect PV Tracker at dawn on a windy day.
A Solaflect PV Tracker at dawn on a windy day.

How do I find out if a Solar Tracker will work at my home or business?

If you are curious about a Solaflect PV Tracker for your home or business, please contact us to schedule a free site evaluation. During a site visit we will answer any questions you have, assess solar conditions, review the condition of your circuit breaker, and check for other aspects such as the presence of ledge that may affect the Tracker’s installation.

The more sunlight that falls on the Tracker, the more productive it will be, and the more value you will receive from it. We use either a Solmetric SunEye or Solar Pathfinder to measure the “solar access” on your property. This is a measure of the percentage of open sky vs. trees/ridgelines/buildings/etc. that block sunlight at any particular location. More solar access means more sun for the Tracker.

Here is an example of an image taken by the Solmetric SunEye.


The image is taken with a fisheye lens, so the outer edge shows the level horizon, and the center of the image is the dome of the sky. You can see that the SunEye—which has built in GPS—has superimposed a curved grid. This grid covers the area of the sky where the sun will ever appear over the course of the entire year.

The curved line closest to the top of the image is labeled as December, showing the path of the sun in that month. It is shorter from left to right than the other lines (the days are shorter in December here in the Northern hemisphere) and it is closer to the edge of the image (the sun in December does not rise very high above the horizon).

The curved line closest to the center of the image is labeled as June. It is longer and shows how the sun in June goes high over head. You can see how the sun in summer rises and sets in the northern portion of the sky, at an extreme in June. The ability of the Tracker to turn and see the sun in the morning and evening when it is in the north is part of its productivity advantage. (See this FAQ.)

Though unlabeled, the path in July is pretty much the same as that in May, August’s path is pretty much the same as April’s, September’s pretty much the same as March’s, and so on.

The roughly vertical crossing lines represent the times of day, ignoring daylight savings time. So you can see that in December at this location, the sun rises at about 8 am and sets at about 4 pm. In June, sunrise is at about 5 am and sunset at about 7 pm.

The SunEye analyzes the contrast in the image and superimposes color coding to indicate whether that part of the sky (where the sun travels) is open to view or obstructed. Where it is open, there is a yellowish tint. Where there are obstructions such as trees, there is a greenish tint. So, for example, while the sun rises in theory at about 8 am in December, at this particular location it won’t be visible above the treeline until 9 am, a loss of an hour of potential solar production each December morning.

The SunEye then calculates the percentage of the grid area that is open vs. obstructed, and gives the result in terms of “solar access.” You can see in the image that this location worked out to have 89% solar access over the course of the year, with variations by season.

We can customize the SunEye analysis, for example to calculate what happens to solar access if one or more trees are removed. In the image below, we have “painted” sunlight over the tall pine tree in the northwest so that the SunEye will treat it as if it were an area of open sky. At this location, removing the pine would provide a gain of 2% additional solar access.


With this solar access information, combined with data on average weather patterns (specifically, average cloudiness), we can calculate how much electrical production you should expect from a Tracker at your property. From there, we can determine the approximate savings you will see on your utility bill. All of this is included in the proposal that we send you shortly after the site visit.

Armed with this information, you will be able to decide if it makes sense for you to go solar with a Solaflect PV Tracker. If you are comparing proposals from Solaflect and other solar installers, be sure to read our FAQ on how to properly compare different proposals so that you make an apples to apples comparison.

How does a Solar Tracker produce more energy than fixed arrays?

Three factors that add up to the Tracker’s overall advantage over fixed-mount arrays, typically around 40%.

Step 1: Longer Days

During the summer half of the year—from the day after the spring equinox to the day before the autumn equinox—the sun is rising out of the northeast and setting in the northwest (in the northern hemisphere). The “ideal” fixed-mount solar array is oriented due south, since that is the way that it will produce as much energy as it can. However, any time the sun is in the northern half of the sky, which occurs in the morning and afternoon for half of the year, the sun will then be behind the fixed array.

The Solaflect PV Tracker, on the other hand, turns to face the sun each dawn and follows it all the way through sunset. In essence, the Tracker experiences a longer day throughout the summer half of the year. The graph below shows how extreme the advantage can be. On the summer solstice here in Vermont, there are more than 3 hours that the Tracker can see the sun and produce power that is lost time to an ideally oriented fixed array. The other days of the summer half of the year are not quite as extreme, but all of them offer some amount of this advantage for tracking.

tracker vs fixed-mount clean v3

This is one of the three factors that add up to the Tracker’s overall advantage over fixed-mount arrays, typically around 40%. (Also see FAQs “Part 2: Face Directly at the Sun” and “Part 3: Shed Snow Automatically.”)

It’s true that this advantage is only available in full to those locations with an open view of the sky from sunrise to sunset. Trees, buildings, or hills to the east and west will reduce the tracking advantage to some extent. We offer free site assessments so that we can analyze your specific site conditions and let you know just how well the Solaflect PV Tracker will perform for you. Contact us to schedule your free site visit.

Step 2: Face directly at the sun at all times

Facing directly at the sun means receiving the maximum of the light’s energy. Sunlight falls on a fixed-mount solar array from an indirect angle at all times of the year except two moments. (The precise moments will depend on the tilt and orientation of the array. The ideal fixed-mount array will be perpendicular to the sun only at solar noon on the two equinoxes.) A seasonally adjusted array that has a different tilt for the summer and winter halves of the year will be perpendicular to the sun at only four moments.

Because of this indirect angle to the sun, some of the potential light is lost. Some passes by altogether, and some reflects off as glare. Read more