Solar panels: Difference between winter and summer

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April 30, 2010

By Bob Difley
solar_panelsThe last remaining snowbirds, except for the hardy “desert rats” that won’t head north until successive days of 100-degree plus temps have turned them into brown lizards, have finally started their migration north to the cooler forests of the northern states and Canada. But Boondocking in the national and state forests presents new challenges quite different from those in the southwestern deserts.

One of these challenges is producing enough electrical power from solar panels to meet your daily needs.In the desert, your considerations are:

  • Because most desert campsites are open to the sky, you get charging from your panels from the first glint of sun over the morning horizon until it has passed out of view in the western sky.
  • However, since the angle of the sun is lower, you will not get full charging unless you tilt your panels toward the sun’s trajectory across the sky, and position your RV horizontal to the sun’s movement, and verify that your panels–or other roof top equipment–do not shade the charging (silicon) part of the panel.
  • Since the days are shorter, your total charging time will be shorter, and your batteries may not have sufficient time to become fully re-charged. Therefore, you may have to schedule more electricity-using hours (meals, showering, computer use) during daylight, so as not to deplete too much from your batteries overnight.

When you move from the desert to a Ponderosa pine forested campsite, your challenges change.

  • Since the sun during the summer months passes more directly overhead, your panels do not have to be elevated to take full advantage of the suns’ rays throughout the day.
  • Days are longer so you have many more charging hours every day than in the desert, and since the number of nightime dark hours roughly equals the eight hours of sleep needed, most electricity-using can be accomplished while the panels are charging–though probably not to full capacity–if you coordinate your sleeping and rising times with the sun’s.
  • But now comes the hard part. Since you are camping in a forest, you will undoubtedly have periods of the day when the sun is blocked from reaching your panels by the magnificent (and tall) trees surrounding your campsite. Short of camping out in the middle of a meadow (which can be nice) you will have to hazard a guess at how many of the actual daylight hours the sun is actually reaching your panels–without any part being shaded which reduces the amount of amps that pass into your batteries–and calculate accordingly so you don’t find yourself with batteries that have not re-charged.

The remaining consideration in both desert and forest is the number of overcast or rainy days which will produce minimal battery charging. It is therefore a good idea to oversize your system to account for all the variables.

Check out my eBooks on Boondocking and saving money on the road on my Web site for more information on living the good life of the RV Lifestyle.

Leave a Reply

30 comments

  1. Mr. Bob Diffy I would like to know the cost of equiping a class A motorhome with solar panels suitable for dry camping

  2. That’s not an easy question to answer since every body is different in their use of electricity. However, there are several Web sites (such as http://www.AMsolar.com that provide work sheets so you can figure out what your likely usage will be and then size an installation that will handle it. The neat thing about solar installations is that if you undersize, it’s easy to add another panel to the system. Just make sure the wiring you use is big enough to handle upsizing. Also try a Google or other search engine search for RV Solar and you will come up with some other sources and work sheets.

  3. 2009 Admiral

    I just had a 130 watt Kyocera panel installed with a Solar Boost controller at a local RV shop that specializes in solar and inverter setups for $1750.00. This place has earned their reputation in this type of work and uses the best supplies and equipment, not a “discount” shop. Your cost may vary.

  4. @2009 Admiral — Don’t tease us with hints around the edges, share the full details if you can so others can benefit: Name of RV Shop, address, phone number?

  5. John Dale

    Bob, I have 160W on the roof and just 2 6V golf cart trojans, average evening use, maybve watch a movie, have an inverter 2000W Pure Sine wave, should I double the batteries???

  6. John – If you have enough power now you may be all right. But you find yourself running short of power, and your batteries are getting up to a full charge early in the day, it might indicate that your system is capable of putting out more power than the two batteries can accept. If that is the case, adding two more Trojans would effectively double your capacity. However, if your present batteries are getting old, wait until you replace them before adding two new batteries.

  7. 2009 Admiral

    Happy to oblige. I had my work done at Pro Tech RV Services, 10125 US Hwy 50 E, Mound House, NV (just east of Carson City) (775) 246-9922. Ask for Terry!

  8. Elaine Cundiff

    We have 525 Watts of solar. It was installed two years ago by Energy Concepts in Sapello NM which mainly installs larger systems on houses. We love our system and since we are full timers we could get a good deduction on our taxes. Everyone has different needs for electricity and I like to use the microwave but we don’t watch much TV. Your installer will want to know how much your demand is for electricity before he can design a system for you.

  9. Howard Olsen

    Bob, I hope it’s OK to mention on this blog that I have a new 170 watt panel and matching 15 amp charge controller on board which we never installed. I may be selling them in the next few weeks as my electrical power needs are undetermined. Will consider smaller battery tender panel in partial trade. We are crossing the country roughly diagonally MT, WY, SD then possibly CO, NM, OK, TX & maybe LA, MS, AL, GA & FL. Thank you for an interesting forum.

  10. fred flinstone

    solar panels kick butt on an rv they work great for free power in the wilderness! why would u not want a system if u really use your motorhome?

  11. Bob Anthony

    Dear Sir,
    We are highly interested in your product bellow.
    Kindly advice if you have in store.

    Product disc : SOLAR ENERGY 230V-24V,123W,123w,130w,75W Solar Panel12V

    I will be glad to read from you with the price of this item listed above.
    Hope to read from you ASAP.

    Best Regards
    Bob

    1101 Lancaster Street
    Baltimore
    MD 21202
    Tel: 410-929-6981

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