Here on the Good Ship America, it’s not the good old days of freedom in the wild-wild-west. With solar electricity, you are not just dealing with electricity (one of the big sources of consumer injury and property loss) but with grid-tied solar, which is the big thing in the last 10 years, you are backfeeding power into the grid which is something that was never planned for (akin to swimming upstream) and something the utilities don’t really like. With solar, you are now a power producer and the utilities demand a higher standard of safety and quality. All sorts of extra rules to ensure that nothing can go wrong and so you are required to do the installation under a building permit with a licensed electrician, and inspected by the local code inspector, but also by the utility’s inspector.
Sooner or later the utility will figure this out and you will get a terse letter (or worse) from them. This is one of the reasons behind the general switchover to the new “smart” meters. Also, on some of the older meters, backfed power is measured as usage and you could get billed for the power you produce in addition to the power you use. The third reason, and the one the utilities really get hot about is the chance you could electrocute a lineman working in your neighborhood during an outage. With modern inverters, this is not possible as a grid-tied inverter can’t operate without a grid waveform to follow, but the utilities and OSHA don’t want to take that chance.
The typical grid-tied type solar system’s one drawback is that it can’t operate during a blackout. “You mean I just paid $20,000 for this solar stuff and during an outage I’m gonna be in the dark just like my neighbors?” Without the expense and efficiency and reliability loss involved with batteries, a solar system can’t run on its own. But wait! There is a new inverter now from SMA with a feature called Secure Power Supply that provides a limited amount (12amps) of power when the sun is shining. No batteries, no extra cost. Also, energy storage is seen as the next big advancement for the solar industry and lots of companies are working on ways to incorporate it into a home solar system. This will be a great thing to help improve the stability and reliability of the grid as well.
One of the big advantages of solar power is its reliability. Photovoltaic solar panels have no moving parts and with our automated, high volume production processes, quality is assured and you can figure on them lasting double the warranty life of 25 years. The trick is choosing a panel manufacturer that will last as long as their panels do – so that (just in case there is a problem) the warranty will still be honored. Your installer will typically cover any service for 10 years which is the warranty life of the solar electronics (inverter). Some brands of inverters (the small ones that mount on the roof) offer longer warranties to try and match the array warranty, but locating hard working electronic circuits on hot roofs is really not conducive to reliability and these long warranties are really just marketing ploys. They may replace these units for free, but they aren’t paying the installers to do the service calls, and do you really want the hassle of someday replacing these modules one by one as they fail – even if it is covered by warranty?
One of the uncertainties in making a decision to go solar is figuring how long it will take to pay for itself – and a factor in that is the cost increases you can expect from your utility. One of the advantages to producing your own electric power is that you “lock in” your cost of power and are immune from the utility cost increases. With our banks ever printing more money – you know inflation will raise utility rates sooner or later. Plus with the costs of conventional power generation certain to rise, higher utility rates are baked in the cake. Where is out future energy going to come from? No nuclear plants are being built. Hydroelectric dams are maxed out. Coal industry is facing stiff new environmental regulations. All the cheap oil and gas reserves are history. Sunshine is on your doorstep, and more affordable than ever to convert into electricity.
It used to be that solar was a limiting factor in the sale of your home, however it is getting to be the opposite now that it is becoming much more commonplace. “How come this nice home doesn’t have solar power?” A home with low utility bills is attractive to buyers and to mortgage lenders. The accepted appreciation due to a solar system is 20 years worth of savings – meaning that a solar system will generally pay for itself outright if you figure the appreciation in home value. What you do need to be careful about is committing to long term solar lease financing that can impede the sale of a home.
Yes, it very well can. Here in the sunbelt, we love our shade trees – and many homes (like mine) are unsuitable for solar because of all the shade. But there are alternatives. I just had to build a nice big shop building to have a place for my solar array! How would you like a solar carport? (I mean “solar support structure”) There is also new solar technology that mitigates the effects of shade so have your local solar pro come out and talk of the different possibilities.
I don’t recommend worrying about cleaning your roof mounted solar panels. If they are mounted at a tilt of 15 degrees minimum, the rain will do a good job of cleaning them. The little gain you would get from cleaning them all the time is far outweighed by the effort and danger of getting on your roof to do it. If your solar array is ground mounted, then it will tend to get dirtier and also hitting it with a hose from time to time is much easier – so go ahead. (solar panels are “dishwasher safe”)
One of the things that makes grid-tied solar so affordable is the 30% Federal tax credit. However many people can’t make use of it because they do not have enough tax liability – so large financial companies have stepped in with no-money down leases which transfer the tax advantages of solar to them and provide the homeowner with attractive monthly payments. There is a catch though – while you are avoiding the probably rising utility payments, you are committing to 20 years of payments on the lease. If and when you want to sell your home, that lease (while very transferable) can become a hindrance to the sale. And besides, the investment value of a simple cash purchase of the solar system greatly exceeds that of a no-money down deal.
The savings you will see from your solar system depends mostly on how you finance its purchase. A cash purchased system will pay for itself in 6 to 8 years typically and will cost half as much as just paying the utility for the warranty life (25 years) of the array – and the array will last 40 or 50 years. (plan on replacing the inverter every 10 to 15 years) You will also need to pay to remove the array every time the roof needed to be recovered. Purchasing with a solar loan will take 15 to 20 years with payments that save you a little off your old electric bill – and is a good way to go if you can make use of the tax credits. Solar leases also takes 20 years to pay for but for those unable to use tax credits is a good long term deal.
Roof leaks can be disastrous. Do not install solar on your roof if it is in bad shape. Removing and replacing a solar array costs about $75 per PV panel, so will really add to the cost of doing roofing. If your roof has less than 10 years of life left, either reroof the area where the solar is going, or wait till the roof is at the end of its life.
There are three basic types of solar systems:
This is the most common type at over 95% of systems since introduced in 2005. The solar array’s power is converted instantly to grid-compatible 240Vac and whatever power is needed by the house is supplied with any excess going out to the utility grid and credited on your bill for later use. The credit is subtracted from your usage (you still draw power from APS at night) and you pay the difference plus the standard service charge each month. Any credits built up at year end (December bill) is paid to you as a dollar credit on your account, but at a low wholesale rate. This system of receiving full retail credit for your excess power is called “net-metering” and is a current point of contention with the utilities.
Because on-grid systems supply power to the grid, they require an extra level of code compliance and utility approval and inspection as well as local permitting and inspection to ensure safety. Sometimes, it is necessary to upgrade older or small breaker panels to meet the needs of backfeeding the solar power into the grid, and APS can use this inspection to require homeowners to upgrade the electrical service to meet the latest standards.
The great advantage of grid-tied (also called utility-interactive) systems is that power does not need to be stored therefore eliminating the great bane of solar systems – the Battery. These systems then are the most efficient, reliable and cost effective way to harvest the sunshine for electricity. You still have all the strength and reliability of the utility grid to back you up, but only are paying the utility for the small “make-up” power you need plus the standard service fee. The utilities are starting to object to this loss of revenue, however they are also benefiting by not having to construct expensive new power generation as renewable technologies have begun to supply most all of the increased growth capacity needed in the US.
The major downside to the on-grid type of system is that because it needs the grid to synchronize to and act as its “battery”, these systems cannot work during a utility outage. One exception to this is the new inverter technology from SMA (SunnyBoy brand) that has a secure power feature that allows it to operate during outages, though at a much reduced power level. It can keep your critical loads alive during the day though, powering your refrigerator, phones, TV’s and computers, etc.
Off-grid systems are the traditional type of solar system and operate separate from the grid. The system has to be big enough to drive the entire load of the home as well as store the power for the periods without sunshine. This means larger power converters (called inverters) and a large bank of batteries. Off-grid systems can easily cost twice what an on-grid system does, while being less efficient and needing regular battery maintenance. Generally, only homes located well outside the service area of utilities are candidates for an off-grid system. However, because land that is not served by a utility is considerably less expensive, it can make a lot of sense to spend those savings on an off-grid solar setup and never pay utility bills again (you will be buying replacement batteries every few years though).
Hybrid solar systems are a combination of both the on-grid and off-grid types and yes, is the most expensive of all, yet can run efficiently and reliably all the time. If there is a utility outage, it continues to run off its battery back which, because it is only used during these events, doesn’t have to be as big as in the off-grid type system.
TYPES OF ON-GRID TECHNOLOGIES:
- STRING INVERTERS (Suny Boy, ABB, Fronius, Schneider,etc.)
- MICRO-INVERTERS (Enphase)
- DISTRIBUTED INVERTERS (SolarEdge)
What is an on-grid STRING INVERTER?
The most common way to convert the solar array power (high-voltage DC) to house power (240Vac) is with a string inverter. So called because the solar PV panels are wired together in a series string so that their voltage adds together to be higher than the AC voltage that the inverter is converting to. This is one of the main reasons why solar systems have become so much more efficient. But because all the PV panels are in series, they need to be the same size, oriented the same direction and shade free. In general, they all work together and are only as powerful as their “weakest link”. Avoiding shade is the best solution. Shade on one panel bottlenecks the rest of the “string” and the losses are compounded. String inverters are typically still the most cost-effective and reliable way to harvest sunshine. These inverters usually come with a 10 year warranty (which can be extended to 20 years) and have the best reliability track records in the industry.
What is a on-grid MICRO-INVERTER?
About 5 years ago, microinverters came into the solar field and have captured a growing segment of the market. The idea is to have an individual little inverter for each solar PV panel. This has the advantage of maximizing the power generated by each panel as it is not affected by its neighboring panels as in a string system. The panels do not have to be matched or the same orientation and shade on one does not affect the others. A good solution for shady Arizona roofs – however, it means installing these sophisticated electronic modules under the solar array where temperatures can skyrocket! While these inverters typically carry 25 year warranties (to give you the confidence to buy them), chances are these will need to be replaced one by one during their time on your roof. Some panel manufacturers are even integrating them right into the panel which puts the normally ultra-reliable PV panel at risk of needing replacement when the microinverter fails. These inverters cost a bit more to buy and a bit more to install, but have the nice feature of being connected to the internet and you can monitor your solar production on each panel. They also have a nice safety advantage in that when the system is shut off – say in event of a fire, the array is shut down as well.
What is an on-grid DISTRIBUTED INVERTER?
In between the string and micro-inverters is a technology where you have a bit of both. There are really two steps performed by an inverter. First it manages the solar power from the array optimizing it for the best voltage and current. Second, it converts (or inverts) the DC power to AC (alternating current) and manages the interconnection with the grid. The SolarEdge inverter system mounts a minimum of electronics with each panel to perform step 1 and then sends all their combined power to a single wall mounted box down below to perform step 2. This provides all the advantages of the microinverter system with somewhat less risk of failures up on the roof.
TYPES OF SOLAR PANELS:
- Crystalline Photovoltaic
- POLYCRYSTALLINE PHOTOVOLTAIC
- MONOCRYSTALLINE PHOTOVOLTAIC (SolarWorld, SunPower, Suniva, Panasonic)
- THIN FILM
- SOLAR SHINGLES (DuPont)
What are POLYCRYSTALLINE PHOTOVOLTAIC solar panels?
This is the standard for the solar industry and is the best choice from a value perspective. Made by freezing liquid silicon into a square crystalline cell, the fabrication process is very fast, but leaves non-uniform boundaries in the crystal reducing its efficiency a bit. Power levels in the standard panel size of 1000x1650mm (39x 65in) are typically around 250watts. Their appearance is also typically a mottled dark blue color, and if fabricated with black anodized frames and a black back-sheet, look very appealing on a roof.
For all types of solar panels, the manufacturer’s label rating is, as you would suspect, the ideal maximum you can expect from that panel. It’s called the STC (standard test condition) rating. The industry also uses a rating called PTC (performance test condition) put out by an independent agency that is more
appropriate for the real world. Solar arrays are typically sized using the label STC rating to be about 10% larger than the actual inverter size to optimize the inverter’s capacity.
What are MONOCRYSTALLINE PHOTOVOLTAIC solar panels?
Mono panels are the efficiency leaders in the solar industry – but you pay for it. The round crystals are grown in a very slow, expensive process used by the electronics industry – but on a larger scale. They are virtually one single, perfect crystal and have better productivity as a result. Monocrystalline panels typically exceed 300 watts in the same size panel as the 250w poly panels. This 20% increase in efficiency may cost you a third or more in price. They have
a more uniform black appearance but are often only available in clear aluminum frames as black framed panels run hotter and photovoltaic panels work better the colder they are. If your roof is constrained on available space, then these higher cost panels may be justified. The new building codes just coming into effect in some areas of the Verde Valley (Sedona and Prescott so far) are restricting solar arrays from the top peaks and valleys of roofs in order to leave room for fireman access. Many newer homes with all the architectural roof features leave precious little space to add a solar array. Mono panels have not been proven to be any more durable and reliable than the poly version. Both types have been in use since the early 60’s and have proven to be ultra-reliable. The industry standard warranty guaranties at least 80% of nameplate power after 25 years, and you can safely assume the panels will produce power for you (and your children) for 40 to 50 years. Be careful that your mono panels have a black back sheet as the cells are a round crystal clipped off into a sort-of square shape leaving a white ugly spot in the corners between all the cells – if the backsheet is white
What are thin film photovoltaic collectors?
The Arizona based company First Solar is the industry leader in this low cost fabrication technique where a photovoltaic medium is sprayed onto a substrate at high speed. The efficiency is quite a bit less making these panels not very suitable for rooftop applications. But for large scale installations (there are now some encompassing 1000’s of acres here in Arizona), they can be the most cost effective though.
What are solar shingles?
Some neighborhoods have concerns about the “look” of solar panels on
rooftops and this technology was invented to make a shingle look very similar to a standard roofing shingle. So far, they are a much more expensive way to install solar (although saves on the cost of roofing) and have demonstrated poor reliability due to the myriad of electrical connections between the “shingles”. Arizona has a state law restricting Home Owner Associations (HOA’s) from implementing any rules that limit the efficiency of a solar installation – so solar shingles can’t be mandated. About the only restriction HOA’s can place on solar is to paint the support structure. The Sedona building dept. mandates black-framed PV panels and painting all electrical equipment to match the home’s décor due to a concern from the balloon tourist industry.
- FLUSH MOUNTING
- TILT RACKS
- TILE MOUNT
- STANDING SEAM STEEL
- GROUND MOUNT
- ELECTRICAL EQUIPMENT MOUNTING
For pitched roofs greater than 15° (3/12 pitch), it is very nice to just mount the solar array directly onto the roof. A typical 18° (4/12 roof is almost the universal pitch used here) will only lose 3.5% productivity over the optimum 30 degree pitch. A panel tilted less than 15° will not self-clean in the rain and is not recommended. A flush mounted array uses mounting brackets screwed through the roof into the framing structure in order to meet the wind loading requirements of the building code. Aluminum rails are then fastened to these brackets with the solar panels clamped down with special devices that electrically tie the whole array together for grounding protection. The array typically sets off the roof surface by 4 or 5 inches which is important to allow cooling air under the array. These flush mounted arrays can typically be seen from the ground and it is nice to use a mounting system that doesn’t stick out on the ends. The best looking arrays are a simple rectangular shape with no sign of the mounting system underneath. The wiring should be secured up under the array, out of harm’s way. Screening systems are available when pigeons or squirrels are a problem.
Unfortunately, very few roofs were designed with solar in mind, and there are often obstructions in the way of vents, skylights and equipment preventing a nice clean rectangle. Your installer should be an expert at finding the most aesthetic way to get the most solar panels on your roof, even if it means re-plumbing a vent or two. Of course, it doesn’t make sense to install solar on a shingle roof that is nearing the end of its life. Our policy is to not put solar on roofs with less than 5 years of life and to require a signed waiver for roofs with less than 10 years of remaining life.
For roofs with less than a 15° pitch (like the many Santa Fe style flat roofs here in the Verde Valley), tilt racks are needed to get the PV panels facing into the sunshine better. Legs are added to rear mounting rails to produce about 20° tilt, lifting the top of the panels to about 24inches off the roof. This can be very unsightly especially from the rear, but most flat roofs have a parapet surrounding them which very effectively hides the array. Also because of this tilt, the rows in the solar array must be spread out (at least 4ft gap between) to prevent them shading each other. The tilt can be lowered to 15° to be less visible at a production loss of about 6%. Roof penetrations become critical with flat roofs and extra flashings and professional roofers may well be needed depending on the type of roof coating involved.
For either flat tile or S-tile roofs, a special bracket is used beneath the
tile to shift the mounting point from where there roof’s framing lies to a point under the center or high spot of the tile. A hole is hammer drilled through the tile at this point so that water will drain away from the penetration. Tile mounts are a time consuming process and cost accordingly more, but of course – last much longer as well. Another option is to remove the tile completely from the area under the array, put down a composite roof so that the solar array sets “into” the tile roof and looks very nice as a result. On new construction, this saves the cost of tile in this area.
Standing seam steel roofs are some of the best for installing solar. A special clamp block attached to the seams holds onto the solar panels and no penetrations are needed – making for a very secure, waterproof roof that lasts virtually forever. Because the array is just attached to the steel roofing, we have to insure that enough nails were used in the mounting the roofing to handle the wind loading of the array. Leasing companies will not finance solar systems for certain types of roofs like this as well as corrugated (tin) roofs, mobile home roofs, or foam roofs.
We recommend roof mounted solar arrays wherever possible as they are safer and less expensive than ground mounts, however, ground mounted arrays can certainly be done. Roof mounted panels generally stay cleaner from all the dust and debris that blows around at ground level, but on the other hand ground mounded arrays are convenient to wash off by hand, whereas we do not recommend cleaning roof mounted arrays at all. Leasing companies will not finance ground mounted systems. Ground mounted systems typically entail substantial foundations to handle the large wind loads caused by these solar “wings” as well as need trenching to connect into the electrical service panel.
A word about mounting the electrical equipment. All of the Verde Valley is in APS territory. Not all utilities require it, but APS requires a dedicated safety disconnect in the solar system to ensure the system can’t energize the power lines during outages when linemen might be working on them. (This is not possible due to the inherent nature of inverters to shut off when there is no grid to synchronize to –but it’s an OSHA rule…). APS also requires a dedicated power meter just for the solar so APS can keep up with their reporting requirements to the RES (Renewable Energy Standard) set by the AZ Corp. Commission. These electrical boxes are to be located near the regular Service Entrance (breaker box) so APS can find them 24/7 when needed in an outage or by a meter reader. When you have solar, you have to grant APS access to this location at any time and it can’t be enclosed by a fence and can’t be accessible by your dog. Sometimes it takes rearranging your fences and gates, sometimes we have to run the solar power out to an accessible location and then back to the service, sometimes we can get approval from APS to locate the equipment somewhere else on the property, but then identify it with a permanent map at the service.
The electrical service has to 5 times larger than solar system’s output to meet the backfeed rule in the electrical Code. This means for a typical 200A service, 40 amps is the max which equates to a 7700 watt inverter. This makes the largest array size for a typical home to be no larger than 9kW. To go higher than this means either upgrading the service to 400 amps (cost ~$1500), downgrading the main breaker to 175 amps (if possible), or doing what is called a line side tap (very few manufacturers allow this in a residential service). If putting solar on a home under construction, please use the new type of electrical panel that is “solar ready”. 100 amp panels are limited to a 3.8kW inverter (4.5kW array). It is very common to have to upgrade these small panels which many homeowners want to do anyway and by making it part of the solar install can be eligible for the solar tax credit as well.
The inverter does not have to be located next to the electric service panel, although this is commonly done. They are made to me located outdoor or indoors – our only rule is to not locate them in the direct summer sun. The inverter is a hard-working expensive piece of electrical gear and it is worth it to baby them a bit. Inside the garage is common, although anytime they are located indoors, the inspection process can be hampered because inspectors generally will not go into an occupied home without an escort. Inverters have a nice display with lots of info on how well the system is performing and it is nice to locate the inverter in a convenient spot where you can check on it as you get out of the car every day for example. Some inverters have built in capability for hooking up to the internet and you can monitor them that way, but others (SunnyBoy) for example figure most people don’t need that and don’t want to pay for it. When solar systems are financed through leases, they always include remote monitoring to ensure the system is working properly because they generally include a performance guarantee which pays you if the system is performing poorly.
There are three ways you can finance a solar system – each with its advantages and disadvantages:
Generally speaking, if you can afford to purchase the system and can make use of the tax credits, you will be way ahead in the long run. If you can’t afford it but can use the tax credits, then a loan (either home equity or unsecured) is the best option and if you can’t afford it and can’t use the tax credits, then a lease is for you. Currently in the US, most residential roof top systems are being ccomplished through the 3rd party leasing companies (SolarCity/SunRun/Sungevity/ Sunpower) SolarCity has great marketing, is now a public company with good access to capital uses in house installation crews, but as reported by watchdog.org suffers in customer satisfaction.
SunRun is a Chinese owned company that only uses its own panels.
Sungevity is not as competitively priced yet has good quality standards.
SunPower is a vertically integrated American company that uses its own panels and rebranded inverters and is known for the highest prices in the industry.
2013 – APS installation rebates ended. At one time, APS was paying $3 per installed watt to encourage the adoption of solar. Now that solar has dropped to less than $3 per watt total and Arizona’s RES program is ahead of schedule, APS has terminated its incentives.
2014 – APS instituted a solar “tax” of 70 cents per installed kW per month.
2015 – APS is threatening to increase the solar “tax” to $21 per month.
2016 – Federal 30% tax credit was due to sunset. It was extended another 5 years.