A tale of solar panels, snow, and roof rakes
Here's a chore I didn't expect to have this winter: removing snow from my solar panels.
As anybody who lives in New England knows all too well by now, we've had a snowy winter. I like snow so, overall, that's just fine with me. But the white stuff delivered an unexpected hit to the electric output of the solar panels I had installed last spring. It's hard to calculate a precise impact, but my December electric bill offers a clue: it's more than twice the previous month.
The good news is that I think I've figured out a system for keeping my rooftop panels humming at full bore even during the snowy season. It adds to my to-do list, but that's the cost of being an aggressive technology adopter, I guess.
In general, solar photovoltaic panels don't need a whole lot of maintenance as there are no moving parts. They usually have warranties good for 20 or 25 years. Cleaning off built-up dust and pollen in the spring or summer is a good idea because that film cuts out a little bit of light from hitting panels, reducing the amount of electricity they make.
But snow is a completely different story. A thick blanket of snow--and we've seen many of those this winter--can all but eliminate electricity production. Sure, some light can penetrate through but the panels produce just a fraction compared to their potential.
A blanket of snow on solar panels--clearing the surface gets the juice flowing again.
(Credit: Martin LaMonica/CNET News)Here's another thing I learned: because of the way solar panels are wired together, a little bit of snow--or bird droppings or leaves--blocking just a portion of an array can dramatically cut the output.
One phone call to my solar installer and a trip to my local hardware store have me and my panels back at full steam. It turns out that a thing I never heard of before--a roof rake--is a clutch piece of equipment for folks like me.
Sparkly snowy morning
Tuesday night it snowed and Wednesday was a gorgeous sunny morning. Distracted by the thought of my covered panels, I took a quick look at my inverter (the machine that converts direct current from your panels to household alternating current) and my heart sunk.
The output was a measly 140 watts--about one tenth of what they would be producing on a sunny winter morning. All those perfectly good photons blocked by 5 inches of fluffy powder!
Earlier this winter, I just waited for the snow to melt from my slanted roof. This works (I suspect most sane people do this) but I was intent on fixing what I saw as a suboptimal situation. After previous storms, snow ended up piling up, frozen hard, on the bottom third of my array, which did a number on the whole system's output.
In December, the production of my panels hit a low point. They made less than a third of the juice than they did in August when the panels covered a large chunk of my household's monthly electricity use.
The deluxe roof rake. When modified, good for snowy solar panels, ice dams, and all manner of debris.
(Credit: Garelick Roof Rake)Now, I'm not blaming snow alone for the lost productivity. Solar panels operate perfectly well in northern climates--assuming you have good exposure and many sunny days a year. But days are shorter in the dead of winter, which means fewer hours of daylight when the panels can do their thing.
Winter weather actually offers some advantages. Photovoltaic panels, like other electronics, work best in the cold. The output of silicon solar panels, the most common solar cell material, starts to go down in very hot weather. Snow also reflects light which, in theory, could end up on the surface of panels.
So I had expected fewer kilowatt-hours this winter but I was still irked by the performance hit. After all, I shelled out good money for these panels--depending on the size, installation for solar electric panels ranges from $20,000 to $35,000 before state and federal rebates--and I want to maximize the electricity they produce to get a return on my investment.
On Wednesday morning, I was prepared. A week earlier, I had bought a snow rake. (These are hot items this year given all the snow and problems with ice dams.) A snow rake--the one I bought was about $75--is just a flat aluminum plate with a long handle. Run it down your roof and the snow comes off.
When I mentioned what the rake was for, the guy at the hardware store cleverly recommended I attach a squeegee-like strip on the bottom so I didn't risk damaging the expensive panels.
My roof rake allows me to reach about 20 feet up. In practice, that means I can only clean off the bottom of the panels; the ones near the roof ridge remain stubbornly beyond my reach. (Be careful of mini avalanches if you try this.)
If Wednesday's experiment is any indication, clearing off just a little on a sunny day is a lot better than doing nothing. With some of the panels exposed, the current starts to flow, creating some heat on the panels' surface and melting the snow. So within a few hours, much of the snow melted, apparently from the heat of the sun and the panels themselves.
With any luck, my electricity bill will go back down to where it was before the snowflakes started falling. So far, it looks like the panels produced 25 percent more electricity in January than in December, when the snow blockage was at its worst. (Other factors like number of sunny days, of course, come into play.)
I confess, I was a little preoccupied with this situation Wednesday morning; I made a few trips outside to quickly clear away the snow after it melted and slid down the panels. By midday, the panels were more or less clear and fully operational.
Yeah, it's one more chore that I need to do after I shovel the front walk. But free sun power is a terrible thing to waste.
Martin LaMonica is a senior writer for CNET's Green Tech blog. He started at CNET News in 2002, covering IT and Web development. Before that, he was executive editor at IT publication InfoWorld. E-mail Martin. 
what deal
not!!
After all, the author mentioned that half his power bill was saved by the things. A typical power bill is ab't $200-$300 for a typical family per month at the cheapest... not counting electric heating if you have/use it, in which case you can expect the bill to double in winter (and you get to eat a smaller hit anyway in summer from air conditioning). Even saving $1k per year gives you $10k at the 10-year mark, paid off at the 20-year mark (assuming prices for electricity don't go up, which they tend to do anyway...)
At the 20-year mark, your panels (if they're worth a damn) are still operating at the 80% mark or so, and will drop to 75% of original output at the 25-30 year mark (this means you can leave 'em up anyway past the warranty).
(and we hadn't even touched on the tax credits...)
To top all that off, if power goes out during peak hours (anyone living in California knows how that can happen), you're still set for at least some power during that time (peak hours are usually from noon to 6pm, IIRC - esp. in summer when everyone has the air conditioning running).
That's 1400 watts in the winter. Summer output will be higher.
Imagine building a new house, but not including insulation or insulated windows because the payback was not fast enough. Just silly. If anyone can afford solar, they should do it.
Also the author is in the northern climate where the effeciency is less.
Is it a bad idea? No, not really, but it's more like having a Prius- it's far better to be the *SECOND* owner of the unit since the first person has to take the hit on the investment.
A) People will actually save money in the long run.
B) When all the power lines are down for days or even WEEKS at a time like they are in KY right now people this this guy will have power. So who is the dumb one?
C) the more people use this the less people are using electricity off the grid. Not to mention any excess power they have is sent BACK ot the grid on many systems. So people like this guy are doing YOU a huge favor. You should be thanking him not belittling his investment.
D) this guy is helping the enviorment by reducing the amount of CO2 he's putting into the air.
I thought $80 last month was excessive. Hurray for hydroelectric power!
http://www.kyocerasolar.com/products/pv_calculator.html
For a $30K investment, and a 10 year expected life for the panels, one would need to save over $3K per year in electricity to break even on the investment, assuming no annual maintenance costs. That seems a lot more kw that the panels produce...
What is your experience on your payback?
I did a quick google on average US monthly electic bill and only found this: http://www.eia.doe.gov/cneaf/electricity/epav2/html_tables/epav2t2p1.html. So in 2001, it was around $70/month. If the solar system covers the whole bill - that would be a savings of $8400/10-year. So a payback would be more than 30 years.
But, of course, that totally ignores the fact that electricity prices don't stay constant. I don't know about you, but my average electric bill is more like $140/month - so payback would be in 15 years. But electric prices are likely to rise further. I expect realistically for solar panels to pay for themselves in 10 years. And that's ignoring the real possibility that solar panels are becoming cheaper as economies of scale kick in.
This assumes that no new power generation occurs or that fossil fuels dwindle (raising its cost). If more efficient, cheaper energy production occurs (especially with all the new interest and investment in renewable energy tech), the price of electricity may not go up as much, or at all, as you might think. Over the short run, I don't think the return on investment in solar is practical right now. Maybe in the next 5-10 years it'll be worth it. The real key is to amortize the cost with the purchase of a house, not as a separate cost after purchase. If you refinanced your house and cashed out enough to pay for solar, it might be worth it (assuming you haven't been paying down the mortgage too long already), since the cost would be spread out over 30 years instead of up-front.
It also assumes inflation and has a historical record to back it. ;)
Am I correct that:
1400 watts x 10 hours/day = 14kwh of power
I pay $0.09 per kwh
Thats $1.25 per day
It would take like 65 years to pay back $30K ($30K / 365 / $1.25)
Even at double the output, or double the electric rate, the payback is still over 30 years.
That neglects:
interest on the $30K investment ($80K over 30 years at 8%)
any maintenance on the panels
chance of damage from a snow rake ;)
As for my use of 10 years as a useful life, I used 10 years as I have little faith in any warranty over a few years. I can't imagine the solar firm being around and honoring a warranty 25 years out. Especially for new technology. (Got 30 year roof shingles on your house? Think that that warranty is worth anything?)
I come a lot closer to a break even on a small wind turbine (I live on a high ridge) than on solar, but even that does not make economic sense.
Now, if the government would use some of that "stimulus money" on some serious tax credits for alternate energy, the whole equation changes!
Another person was right in pointing out that the panels degrade over time. This is not something that can bet stopped or ignored, and is something you didn't include in your earlier calculations either.
You did not include replacement costs, repairs, or maintenance.
There's a lot that you missed. It's easy to gloss over the facts if you only read the sales brochure for a company's product. I would suggest you take a look at the many solar energy forums and sites out there for a more balanced approach. In some installations it makes a lot of sense. Currently, the cost of production of the units makes it very very expensive to use at this time unless you are in the sun belt- something even Portland isn't in. :/
Check your warranty. The full output of the panels is NOT guaranteed. Typically perhaps 75% of the output is guaranteed for 30 years.
The correct way to financially analyze an investment is to use net present value, not the payback period. With net present value, a dollar saved today is worth much more than a dollar saved years in the future, which makes economic sense (the relationship is the discount rate).
Today, you can easily invest in high quality tax exempt municipal bond funds that yield 7% by purchasing a closed end mutual fund on the New York Stock Exchange. You can do even better if you go with funds with lower quality municipal bonds, many of which are yielding 10% or more.
This is INCOME TAX EXEMPT INCOME. OK, a $30,000 investment will pay $2100 per year tax free. If your electric bill is $150 a month, that is $1800 per year.
Your electric bill does NOT disappear if you have solar panels for obvious reasons. When it rains, snows, is overcast and at night the panels make no power. Thus, the solar installation does not make power that will cover the entire bill for your $30,000 investment. You still pay something to the utility every month.
Also, with solar panels, the mainteance is your responsibility. The inverter, for example, will fail periodically and need to be replaced. If your are not a do it yourself sort of person, you will pay for someone to clean the solar collectors on your roof and do all the other maintenance. Remember that maintenance is included in your utility bill, you do not pay extra for the service. There may be extra home insurance costs as well for a solar installation, this needs to be checked out with specific policies.
Every year, people die or are hurt falling off of their roofs installing or maintaining solar installations. Be careful.
Remember that the output of your panels is going down every year, so your benefit is declining every year. Also, the "rated" output of solar panels is never achieved in a real installation in the USA. Typically the peak output is on the order of 85% of rated. Again, read the specs which have fine print specifiying "typical output". Use the typical output figures when planning an installation. When you buy a 100 watt solar panel and paying $5 per watt, you are really buying only an 85 watt panel and paying $5.88 per "real watt".
The reason: Solar panels are tested indoors illuminated by test lamps that are supposed to simulate the sun on the equator at solar noon. The solar cell junctions are maintained at around 75 degrees F. Now, remember that the output goes way down when the semiconductor junctions get hot. On a summer day, the junctions will be 120 degrees F or hotter on your roof. Even in the winter they can get very hot. Obviously, in the winter the sun is at a lower angle in the sky and the intensity of the light is less also.
It is difficult to make a good economic decision with solar products advertised and sold as they are today. Few consumers understand the complete story. After 10 years, the product will produce only 90% or less of its original output, and after 20 years it will be only 80%. (Remember that original output is the "typical" number, not the rated number.)
There is going to be a consumer backlash eventually that will make full disclosure of what you are buying mandatory, I am sure. For the time being, buyer beware.
What happens during the summer is that the water in the thermal water heater part of the solar panel pulls heat from the solar panel cooling it off and upping efficiency of the solar panels in hot to really hot weather.
I don't know the name of the company nor do I work for them.
I think this is a great idea as thermal water heaters pre-heat the water you use and run it in a loop through you water heater. This way your hot water heat has a lot less work to do. With this combined into solar panels it makes them more efficient too. This is a Win/Win deal.
Cite please.
"The full output of the panels is NOT guaranteed. Typically perhaps 75% of the output is guaranteed for 30 years. "
A typical single high-end panel can produce up to 175 watts each nowadays. 30 years from now that still gives me up to 130 watts per panel... and that's lat least 10 years after the thing has paid itself off.
"The correct way to financially analyze an investment is to use net present value, not the payback period. "
If that's the case then we should skip buying a house and just buy a small plot of land and some bonds... of course, living in a tent is going to suck, but wahey... ;)
The point isn't to justify it as an investment of money, but as a means to put in something that will pay itself off over time and at the same time act as insurance against higher power costs, brown/blackouts, and the like.
"Your electric bill does NOT disappear if you have solar panels for obvious reasons."
Nope - but it certainly will be smaller, and rate hikes won't bring as much grief. It's also nice to have something on hand when the local power supply dies off for days on end.
"The inverter, for example, will fail periodically and need to be replaced."
Cite, please.
"If your are not a do it yourself sort of person, you will pay for someone to clean the solar collectors on your roof and do all the other maintenance."
e.g. wash them off with a hose occasionally, and brush the snow off with a big rake. Well gee... that's rather technically complex to do, isn't it? ;)
The rest is a FUD-fest, with no supporting evidence at all. Maybe you can produce something to back up your statements?
/P
"The rest is a FUD-fest, with no supporting evidence at all. Maybe you can produce something to back up your statements? "
I think people are still waiting for *YOU* to do that. :) I know, I know, someday you will, but I don't expect it to happen any time soon. Why break tradition?
So for that maintenance- you recommended that all that is needed is using a garden hose and a snow rake. I decded to check that out myself online. Did you know there's this thing called 'Google' and it connects to the 'internet'? Amazing stuff out there. It took less than 30 seconds to find out that you need to have your system maintained by a professional electrician and inspected. Some communities vary on the inspection cycle, but it's not something you can do yourself. You have to pay for this service. You also need to have your inverter serviced regularly as well. It needs to be certified and recertified regularly.
Contrary to your recommended 'maintenance', spraying down an inverter while in operation would be a horribly bad idea and one that I hope that you do not honestly believe needs to be done. Let professionals do the work.
Your numbers are..... creative. Your comments have proven you have very little knowledge of the subject and a little knowledge is very dangerous indeed. Soemone following your advice could lead to very deadly results, I'm afraid.
Now if you had a system that tracked the sun throughout the day, and over the seasons, you might have an option to set the panels in a vertical position during snow storms so the snow doesn't accumulate. After the storm, return them to their regular tracking pattern.
Enphase Energy
http://www.enphaseenergy.com/
Since 2004, solar prices have been propped up by a shortage of capacity to make both silicon ? the raw material for solar-power systems ? and finished panels. Meantime, the Spanish and German governments have paid system owners hefty subsidies to generate solar power, turbocharging sales in those countries.
Manufacturers responded by building a wave of factories. Then Spain and Germany slashed this year's incentives. In the U.S., the biggest solar investors were banks such as Morgan Stanley that can no longer benefit from tax credits because of insufficient profits.
New Energy projects an oversupply of nearly 4 gigawatts of solar modules in 2009, or enough electricity to supply 2.6 million homes.
The glut is already dragging down prices. Barry Cinammon, CEO of Akeena Solar, one of the nation's largest installers, says wholesale prices have fallen about 15% since October. Since installation accounts for about half the cost of a system, total costs are down about 8%. SunPower,one of the largest manufacturers, expects retail prices for its solar modules to dip as much as 20% this year.
"Now, all of a sudden, we have module manufacturers calling us," says Peter Rive, chief operating officer of Solar City, the No. 1 installer.
Consumers can reap even bigger gains if they can buy in a recession.
Until this year, homeowners who bought solar systems were eligible for a tax credit that shaved system prices 30%, but the credit was capped at $2,000. Last fall, Congress renewed the 30% credit and removed the cap, lopping thousands more dollars off solar price tags.
In California, which accounts for nearly 70% of the U.S. solar market, a typical 4-kilowatt, $32,000 solar energy system cost a homeowner about $23,000 last year after state and federal incentives. This year, if prices sink as expected, that system is likely to cost $10,000 to $12,000.
If you can afford the initial $20-30K+ out of pocket, then you are rich enough not wo have to worry about the money you might save in the first place.
These are the simple economic realitities of the current situation.
This shortsighted "thinking" is why everything is coming to a head now.
All that sad, we have a perfect location for solar panels (large south facing roof pitched at a very decent angle) but will likely go with a water based system instead. Why? At least for now it is cheaper to install since I can do most of the engieering myself. But, maybe based on "true" financials, a PV system would be better, even though it'd never "pay back" in our case. But, we only have one environment and every little step we take will help.
ive collected daily production data and even without counting snowfall-production-reductions, december production numbers go way down anyways, probably b/c of the shortest daylight times of the year is in december and plus we get all more cloudy days in december too. The new england area should get the same cloudiness too. So my point is that snow cover normally isnt a big cause of reduced production in december.
The also make rakes with plastic blades, might be a better idea. $20 at HD or WMT.
- and your roof. Every year we see collapsed roofs when it starts to rain after a snowfall because of the immense added weight of the snow absorbing the water and increasing the bearing load greatly.
Even if you don't break your roof, you're asking for a lot of roof damage and water leaks by trapping that water instead of letting it drain naturally. Talk to any buildier and they will cringe at the thought of spraying water on a snow covered roof. But then again, some may recommend it- since they will be getting more business out of you to repair the damage as a result. Heh.
The American and International Scientific Community has yet, over the last FOURTY (40) years of research, grants, gifts, government $$$, invented inexpensive solar panels to the point where you DON'T have to calculate the cost/break-even/maintenance over TEN(10) Years!!! TEN YEARS!!!???
Ping me when it's down to Three or Four Years.
Thank You.
The question is really which of these two options costs less:
A. Borrowing $30K for a solar panel system that will generate a certain number of kwh of electricity over a given period of time
or
B. Buying that same number of kwh of electricity from the electric company, over the same period of time
One needs to make assumptions on:
- the cost of money (interest rate) for the $30K
- how long the solar panel system will last
- what electric rates will do over time
- what maintenance or repairs, if any, the solar panel system will require and what that would cost
- what percentage of rated capacity will the solar system produce (sunshine level, efficiency degradation over time, if any)
- how one feels about use of fossil fuels, carbon footprint, etc.
- what savings would investing in energy conservation measures produce (insulation, new appliancces , etc.)
I suspect that each individual considering solar must make their own assumptions, and run the numbers to see how the two options match up.
http://www.mygreathome.com/fix-it_guide/heat_tape.htm
yep, you'd have to add them in the fall and remove them in the Spring to allow for Summer cleaning. Tiny lose in kilo watts, big savings in time. Safety risk for this twice annually task, fairly high.
2- Solar water heatin is also more efficent then solar-electric and is worth adding at the same time or alone.
It is all a matter of not letting corporate interests do your thinking for you.
- by don509 February 10, 2009 5:38 PM PST
- Ah, what fun. Reading some of the venom in these comments is more fun than falling off a roof. I absolutely agree with the absence of metal on a snow rake, maybe the fiberglass telescoping pole for cleaning a swimming pool would be light enough, and not conduct electricity.
- Reply to this comment
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(50 Comments)Who sold this system that didn't advise you that a "blanket of snow in New England", is in fact a light blocking blanket and is going to be something a New Englander will need to address frequently?
I've lived in New England for 40 odd years and my garden hose is stored in the basement during the winter, so there will be no hosing down panels until the spring thaw.
Folks, this is not really the place to thump your members on the table to achieve some perceived rise in the CNET comments pecking order. This is a place to share ideas for a better today and a better future. Sorry if that's to hippie for you. One of us should devise an inexpensive attachment to the upper edge of the panels that will melt the snow. How about some verticaly mounted smallish mirrors? Snow will fall off of them and they can direct the early morning sun onto the snow covered panels, melting the snow without needing a snow rake. Or at least a small vertical (very small) PV unit that can power the heat tape that a couple other readers mentioned? Baby steps, my brothers and sisters.