snow-on-solar-panels-5-dayseditors-blog-entry3As you might know, I’m on a mission to see how much solar generated electricity we can save by sweeping the lower of two solar arrays that together make up our 5.59 kW rooftop system.

On Jan. 9, six inches of white powdery snow fell on our Colorado rooftop. This was followed by two bright, sunny days with high temperatures in the teens, and a third mostly sunny day with a high of about 30.

This past Thursday, was the fourth sunny day since the snowfall. Temperatures pushed into the 50s. Yet, it took until about 2 p.m. for about half of the snow on our upper array – which I cannot sweep because I cannot safely access it – to melt.

In short, after four, full sunny days after a six-inch snowfall the snow still had not melted entirely off of our upper array.

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Sweeping snow means 40 kWh
With the help of a TED system and Google PowerMeter, I’ve been keeping track of how much electricity we’ve generated as a result of me sweeping snow off of the lower, 13-panel array. I’ve done this twice now. So far, as you can see in the table below, we’ve generated 40 kWh we would have lost to snow cover as a result of my sweeping.

This also means that we’ve lost roughly 40 kWh because I have not been able to clear the upper array of snow.

Had I not swept either array after the last two snowfalls here in Aurora, Colo., we would have lost approximately 80 kWh of production – and we’re only halfway through January.

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Assuming similar scenarios for future snow storms – snowfall, followed by a few days of cold but sunny weather, a reasonable assumption through the third week in February or so for Colorado’s Front Range, and assuming two more similar storms, we’re talking about 160 kWh of lost production if I did not sweep at all.

Four snowstorms = – 320 kWh
Increase the snow-events to four, and assuming 80 kWh of loss each time, and you’re talking about 320 kWh. That’s a whole month’s worth of electricity for us, or, if you’re doing the EV math, well over 1,000 miles of driving in an electric car.

Is it all worth it, if you break your neck, or arm, or damage the solar system?

No.

But what we are discovering is that you can lose a significant amount of electricity if you wait for the snow on your system to melt, in particular if you live in a climate similar to ours where it’s quite common for a snowstorm in winter to be followed by several days of bright, sunny weather that’s good for producing electricity with solar, but where it’s often be too cold to melt the snow off a solar system, at least snow on a roof with a pitch as low as ours, which is 19%.

Stay tuned …

Sweeping the snow off solar – An ongoing tally of kWh gained

Snowfall date(s)

Snowfall Amount

Date and time of snow sweeping (lower of 2 arrays of 5.59 kW system only)

Estimated kWh gained from sweeping (gain may have been across multiple dates)

Dec. 30-31, 2010

2 ½ inches

Jan. 1, 2011
12:30 p.m.

7.3 kWh

Jan. 9-10, 2011

6 inches

Jan. 10, 2011, 8:30 a.m.

33 kWh

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