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I am new to all this, had the System installed in October, (Enphase IQ8X microinverters, REC460AA Pure-RX panels, clear west exposure), currently producing less than I’m using. I am wondering if my spring, summer and fall production will even out my winter usage? In other words does all this eventually equalize to make my electrical purchase cost near zero?
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Ah-yup. We had snow overnight and I got about 2" of white crap covering my panels. Where I would normally get 7-8kW of power, I am getting 0.49kW, and that was with me going out with a snow rake and pulled as much snow as I could reach from the lower panels.
The other item to consider is the axis of the planet to the angle of your panels. The sun is much lower on the horizon for now and, though the sun is blazingly bright this morning, it is still too low on the horizon, the panels just cannot produce much for more than 5-6 hours a day. Folks on this blog recommended I look at Time and Date to determine when my home will be back in a solar-positive tilt. We stopped positive solar production around November 10 (the house began using more power each day than the panels were generating). Given that the whole house is electric and we ARE in Winter, I don't expect to be solar-positive until sometime in mid/late March.
Take comfort in knowing that your panels are offsetting SOME home usage for the time being.Rade Radosevich-Slay
Tiverton, RI -
Thanks for your response. How do I figure out when I reach a solar positive tilt? By the way I am Lao on the east coast, on Long Island, NY. Also I have a snow rake but was told to not clean the snow off the panels because of possibly damaging them. Evidently you have not had a problem doing that.Comment
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Hello! Go gentle with the snow rake. I have an extension pole and I just set the rake into the snow and drag what I can without applying too much downward pressure. We have two arrays on the front of our garage, and last year I managed to get covered by an avalanche when the packed snow let go... The more you can pull down ahead of time...
How I determine solar positive or not is to look at the meter. I am a retiree and more or less have nothing else to do with my mornings... I've been taking a meter reading around 7AM every morning. If that number has gone done from the previous day, you are solar positive. If it goes up, you're pulling from the grid.
Our system is Generac, and I have the inverter app running on an iPad. I watch when the panels start to fire up in the morning and when they go to sleep at sunset. I consider consistent generation over 6.0 kW or 30kWh for a given day to be positive production, and on days when we are solar positive, the panels are producing at least 8 hours a day. Right now, we are at around 5 hours. During peak solar season, we can easily generate 70kWh of power per day, about 2/3 of that goes out to the grid for net credits.
As I mentioned, our house is all-electric, so with the heat-pump furnace and HW running, we easily chug through 60kWh of power a day (plus charging an EV). If we did not have to heat the house, that number would be considerably lower.Rade Radosevich-Slay
Tiverton, RIComment
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Here in northern IL, other years smoke from western fires definitely
impacted solar production, more than mild clouds. Yesterday I
observed a near clear sky at mid day, optimum cold panel operation,
but production was down nearly half. I am quite sure smoke was
responsible, though not very obvious. Bruce RoeComment
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1.) If you have a Net Metering agreement of some sort (an "NEM") with your POwer COmpany ("POCO"), your high and low generation per billing period will tend to be evened out over what's usually one year.
2.) However, as to a zeroed out bill, that's largely a function of system size, the weather and your system's ability to produce power vs. your use of power.
If your system is sized to produce as much or more than you consume, you will get close(r) to a small(er) bill.
If sized to produce less power less (that is, a smaller system), your remaining (residual) bill will be higher.
However, the way NEM's are structured these days, it's possible or even likely that even if your system produces as much or more than you use over the course of 12 months, you will still wind up owing the POCO money although it will most likely be less than what you'd owe if you didn't have the PV system.
Some /Most? NEMs are structured so as to pay a very small credit per excess kWh produced by the system and then sent back to the POCOe as overproduction with any annual surplus production either carried over to the future or lost.
READ the NEM you most likely signed on to but probably didn't read or know about much less understand - those things tending to be rather cryptic.
3.) If you would like a reasonable estimate (probably +/- 10% or so with reasonably representative user inputs to the model) of what your system "might" produce over a "typical" year check out something called "PVWatts" on the net.
It's actually a user friendly design program from NREL, but most folks use it as an output estimator.
Just read ALL the help screens a couple of times, get your inputs as close to what your system is/has and do a few runs.
Most folks find the model fairly straight forward to use and the results fairly close to what you might expect from your system over time.Comment
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X2 on using PVWatts. My small sample size of 3 years shows it to be very close to real life results.Comment
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I have been producing power since Nov 2011, over 13 years now. I used PVWatts to project production using .71% panel degradation per year along with all the other assumptions built into the site. Predicted production to date was 302.6 MWh and I have actually produced 299.4 MWh. 13 year difference of only 1.1% in total. Pretty good IMO.Comment
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The cause of that difference could be....
1. The .71 panel degradation per year could be slightly low.
2. The weather could be slightly warmer and or cloudier than predicted.
3. POCO outages more than expected...around 5 to 7 days of outages in 13 years.
4. More dust accumulation on the panels from the atmosphere.
5. Equipment downtime for maintenance, less than 3 days.
6. Wire losses due to distance panels to inverters....over 300'
7. Transformer based inverters less efficient than projected probably due to heat.
8. Measurement tools not calibrated exactly to be in sync with each other.Comment
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