# Solar energy production summer compared to winter



## thestartupman (Jul 25, 2010)

Does anyone have documentation on their solar production comparison between winter, and summer, that they would be willing to share? The best information would be with those that have Missouri, Arkansas, or Tennessee type of climates. I know that when calculating solar needs many times it is suggested to average your monthly usage, but in my current situation, a 3.4 KW system would be all that would be needed all but the summer months. I know that the only true difference in the summer months is the A/C usage. I guess my real question is, if I were to get a 3.4KW system that would run my system 9 months of the year, would I get enough production to allow the use of a window A/C unit during the long sunnier summer days? I know a person could learn to go without A/C, but it would sure be nice to be able to sleep comfortably. Any info would be great.


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## Steve_S (Feb 25, 2015)

A few BIG differences that keep production up. 

Fixed Mount (roof or pole) works the "averages" as typically a fixed mount is set between optimum Summer & Winter angled. 

Adjustable Mounting allows for optimal angles for summer & winter angles increasing production.

Tracking Mount gives best production year round as it tracks sun angle for optimal performance. This of course costs more up front but saves adding panels or manually futsing with panels.

MPPT Solar Controller IS the only way to get the best bang for solar production... Ignore the old PWN Charge Controllers. Should be noted that a decent MPPT Controller will allow for a bit of over panelling and it's capable of dealing with it and this is fairly common if not standard in my Region (North Eastern Ontario Canada).

Should be noted... Some of us are able to use (take advantage of) Snow Reflection to increase Solar Production which might surprise those that cannot... It can be quite significant.

ON A/C. Not all AC units are as efficient as they should / could be. Make sure you have a good efficient unit. Portable Units do tend to be more efficient than stock "window conditioners" but they are still hard on Solar Systems. The most efficient way to reduce AC & Winter heating costs is insulation to keep the summer heat out and winter heat in. It's an investment that costs you once with no recurring bills and pays back year round.

SPECIAL NOTE TO CONSIDER:
If you haven't already got an Inverter/Charger unit, seriously consider an RV/Marine class Inverter/ Charger which can put out the amount of wattage you need but which also has a built in battery charger from "shore power" (aka Genny Power). Many have the ability to auto-start the generator if batteries hit programmed threshold. (Should never let batteries go below 75% charge). Here is an AIMS 3000-Watt-Pure-Sine-Inverter-Charger-24-Volt *PURE SINE WAVE* is best for anything electronic and preferred for motors / compressors. Many motors including compressors don't operate very well on MOD WAVE and actually waste a lot of power & can damage cheaper motors as well. Myself, I have an "AnyPowerCorp" Combi 3kw/24vdc Inverter/Charger (not avail in USA) but very similar to this one www.powerinverters.com USA 3000watt-pure-sine-auto-transfer-switch-charger-12v-120v-acdc except I run off 24VDC.

Battery Config: 12Volt is ok for basics, 24Volt for most needs but not for ongoing big heavy loads, 48Volt will handle pretty much anything required and above that if your heavy use. Most Common in solar installations (year round) is either 24/48 volt configurations.

Hope it helps


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## wy_white_wolf (Oct 14, 2004)

Averaging your monthly usage is only recommended for grid-tied systems. For off-grid you need to use true monthly usage and run the calculations for at least the highest usage month and lowest insolation month.

WWW


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## thestartupman (Jul 25, 2010)

I guess I forgot to mention that this will be a off grid setup. I believe the 3.4KW would do fine year around if I didn't use any A/C at all. I can keep everything running on the 3.4 KW for every month that I do not use A/C. I end up with three months of A/C use that my usage sky rockets way past this average usage, and 2-3 months more that will bump up just a little over what a 3.4 KW will handle, and that is only because of the little bit of A/C usage at the beginning and ending of the warm season. I know I could just not us the any type of A/C and seal with the heat just as it use to be when I was growing up, I just don't want too. I was just hoping with the extra sun light in the summer when things are the hottest I might get enough extra production to handle a smaller efficient A/C unit. I will be looking at changing the tilt angle during the different seasons, but do not have plans to use a tracking system.


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## lynnemabry (Dec 28, 2013)

Another difference in usage between winter and summer for us is the amount of power used by the fridge and freezer.


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## Explorer (Dec 2, 2003)

A auto defrost or no-frost freezer requires a lot more power than a manual defrost freezer. The auto feature uses a heating element inside the freezer itself. Most forms of electric heat and solar do not mix well.


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## markt1 (Dec 15, 2013)

Virtually all solar off-gridders have a small generator to maintain the batteries for times when there is no sun for weeks on end. And that even assumes you will brush off the panels in winter.


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## markt1 (Dec 15, 2013)

Virtually all solar off-gridders have a small generator to maintain the batteries for times when there is no sun for weeks on end. And that even assumes you will brush off the panels in winter.


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## red-beard (Jan 10, 2016)

markt1 said:


> Virtually all solar off-gridders have a small generator to maintain the batteries for times when there is no sun for weeks on end. And that even assumes you will brush off the panels in winter.


This is the case. I manufacturer Hybrid Solar Energy systems which combine PV Solar, energy storage, utility power (if you have it) and a generator, all in one compact package. 

By having the generator, you can seriously downsize the battery bank to just the excess from the solar panels. Plus if you have cloudy days, the generator will cycle on and recharge the batteries, then shut off.


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