I assume it is normal to have poor production up north during the winter?

[J.P.M.]

I'm in the Twin Cities. As a data point, during February 2017, I produced 395 kw-hrs; but produced only 49 kw-hrs in February of 2018 (88% less). Over one-third of this month's generation came-in just today. It's pretty meaningless to look at 6 weeks of winter and try to guess what the system will produce over years.

Climate's what you expect weather's what you get. Back in the '80's, in Jan., Buffalo could expect about 60 hrs.during the month when the sun cast a shadow. I just looked back on my records and for Jan. '82 I recorded 22 hrs. when the sun cast a shadow. Jan '88 was a real anomaly. For that month I estimated ~ 150 hrs. when the sun cast a shadow. All that's little more than anecdotal, but variation under similar methodology has some use.

49 vs. 395 hrs. is a lot more quantitative but still not nice.

[specialgreen]

Climate's what you expect weather's what you get. Back in the '80's, in Jan., Buffalo could expect about 60 hrs.during the month when the sun cast a shadow.

We get weeks of cold in a row, so a single snowfall can be a big factor: our panels can be covered in a 4-inch snow layer for weeks at a time... until the next warm spell.

[bcroe]

We get weeks of cold in a row, so a single snowfall can be a big factor: our panels can be covered in a 4-inch snow layer for weeks at a time... until the next warm spell.

Right which is one reason to use a ground mount. Snow at night, my panels are clean by
the time the sun comes up. Bruce Roe

[Ward L]

I live in Southern California and my actual production varies by 70% summer to winter. The estimated production calculation varies a similar amount. The further north you live, the less your winter production will be compared to summer production. (Particularly if your panels are covered with snow!)

[peakbagger]

I have two arrays manually adjustable for angle. I adjust them for winter, Spring/Fall and Summer around the solstices. I should be adjusting my arrays any day now from winter (30 degrees off vertical) to spring/fall (45 degrees) but I generally do not do so despite the higher sun angle as in my area we have a good chance of significant snow the entire month of march. I really dont lose that much production as there is still snow on the ground so I get some reflection off the snow.

Even with the panels at winter angle I do get snow on occasion that will take a couple of days to self clear. That happens in mid winter when day time temps stay well below freezing. This time of year if I get snow, the daytime temps usually make it over freezing in day or so, so no need to rake off the panels.

[J.P.M.]

I live in Southern California and my actual production varies by 70% summer to winter. The estimated production calculation varies a similar amount. The further north you live, the less your winter production will be compared to summer production. (Particularly if your panels are covered with snow!)

Over the course of a year, every location on earth will receive just about the same amount of daylight and darkness, about 4,380 hrs. or so. The farther north (or south in the southeren hemishere) a location, the more dichatoumous the distribution of that daylight will be summer to winter. The limits are at the equator where dayight and darkness are both equal at 12 hrs./day with no daily variation over a year, and at the poles where daylight and darkness are also equal, but with each one being about 4,380 hrs. long.

As a general point, the farther a location is from the equator, the more the daylight distribution will shift to favor summer daylight and so more solar production in summer, less in winter.

In general, more northerly (or more southerly in the southern hemisphere) locations will usually benefit more from seasonal tilt agjustments than locations closer to the equator 3 reasons: More favorable average incidence angles, the higher tilt angles in snow season helping to clear snow from device surfaces, and also by taking better advantage of possibly greater albedo from likely/possible surrounding snow cover.

[bcroe]

Over the course of a year, every location on earth will receive just about the same amount of daylight and darkness, about 4,380 hrs. or so. The farther north (or south in the southeren hemishere) a location, the more dichatoumous the distribution of that daylight will be summer to winter. The limits are at the equator where dayight and darkness are both equal at 12 hrs./day with no daily variation over a year, and at the poles where daylight and darkness are also equal, but with each one being about 4,380 hrs. long.

Interesting, my log says over 4 years, my inverters received enough energy to run for 4310 hours a year.
At 42 deg lat here. Bruce Roe

[Tony.O.AE]

Do you both have solar?

[bcroe]

Do you both have solar?

Sure, but everyone has something different. Bruce Roe

[J.P.M.]

Do you both have solar?

If you mean Bruce and I, the answer is both of us have PV systems. Bruce's is a larger ground mount and more extensive than mine and most others. I also have solar thermal in addition to PV, both rooftop.

Why do you ask ?

[reader2580]

I was home yesterday and took a look at the inverter and saw that I was producing just over 5KW which is really good compared to other times I have looked at it. I do not have the ethernet connected to the inverter yet so I can track production.

[J.P.M.]

I was home yesterday and took a look at the inverter and saw that I was producing just over 5KW which is really good compared to other times I have looked at it. I do not have the ethernet connected to the inverter yet so I can track production.

The output should generally continue to improve as the sun gets higher in the sky, making the solar incidence angle with the array smaller. The days are also getting noticeably longer making for longer collection time/day. PVWatts will provide some general guidance as to how array output may change over a year.

[reader2580]

My production has improved considerably over the past few weeks with more sun and no snow on the panels. My smart electrical meter still shows I haven't sold back quite as much power as I have consumed since the system was turned on 8 weeks or so ago. My panels are supposed to be sized to overproduce by about 1/3 to cover the usage part of my bill plus the $20 or so in fixed fees.

PVWatts shows I should produce about 3,000 KWh more than I consume to cover the fixed fees on my bill.

[J.P.M.]

My production has improved considerably over the past few weeks with more sun and no snow on the panels. My smart electrical meter still shows I haven't sold back quite as much power as I have consumed since the system was turned on 8 weeks or so ago. My panels are supposed to be sized to overproduce by about 1/3 to cover the usage part of my bill plus the $20 or so in fixed fees.

PVWatts shows I should produce about 3,000 KWh more than I consume to cover the fixed fees on my bill.

Using what's close to the worst generation time of the year to guess at annual generation is not a reliable method. Give it a full 12 months.

You sure about your math ?

[reader2580]

Using what's close to the worst generation time of the year to guess at annual generation is not a reliable method. Give it a full 12 months.

You sure about your math ?

I get paid 12 cents per KWh for power sold to the power company and my budget plan for power before solar was $744 per year. I use about 4,750 KWh per year and PVWatts says I should produce about 8,500 KWh per year for total of about $1,050 in production. I have to pay a new $7 per month solar fee now.