A tale of solar panels, snow, and roof rakes

Solar panels and snow don't mix, as CNET News' senior writer Martin LaMonica learned. But with a new tool and a little effort, his home solar-power system is back at full steam.

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. 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. 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.

 

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