I'm happy w/ my small 200 watt solar, but it dawned on me the other day that if the sun hangs in here as long as I do (here in QZS) I will have saved a whole $60 of gasoline I usually burn in my Honda 1000 in a couple months. Not a terrible return on a $300+ solar investment, I thought.But when I found myself going after my 2nd tank of propane @ 50 bucks a trip, I realized something about this self sufficient solar ain't workin quite right.Just curious, how many are running their electric heates on some of these chilly nites,.....meaning how many more watts of solar do I need ? :)Or maybe a better question,...how many solarers are still buyin propane. Maybe we don't have this solar all figured out yet ??

Its all about ampere hours in vs ampere hours out. A 200 watt solar is not going to power a 1500 watt heater very long.

Is the question "can I run an electric heater off my solar system?"You can briefly but trying to build an off grid solar system to power electric resistance heating is impractical and expensive for a permanent home. It's an even worse proposition in an RV. The main problem is storage. That's what's hampering the whole solar industry right now. Battery technology is terribly inadequate for heating.To give you a reference point, 2 golf cart batteries in series hold about 2,640 watt hours of electricity. A 20 pound propane tank with 4.7 gallons of propane holds the equivalent of 126,000 watt hours. So, you'd need 96 golf cart batteries to hold the energy in 20 lb LP tank.

What I had to do was setup my battery banks to run all the thing I wanted to run during the one day/night battery run then successfully re-charge my battery bank each day using my 2KW Honda Generator to power up my OFF-ROAD trailer which will recharge the batteries in a quick three hour generator run time using smart mode technology.Once you get very successful doing this then you can start adding solar panels to keep from having to run the generator every morning for three hours.The 120WATT SOLAR Panels will only give you around 5-6AMPS of useful current so when you do the math you find out you are going to need several solar panels if you want to have your bigger battery banks charged up to their 90% charge state in order for you to make the next day/night run off the batteries.I have found out I have to have my generator on-board as it will charge my batteries rain or shine. Just a couple of Solar Panels are not going to give me 90%-100% charge of my batteries during a one day HIGH SUN day where we usually camp at... It may be cloudy for a whole week haha...If you just want to run a light or something small then your solar only will work for you. If you want to run all the things you want to run in the one day/night run it will take many solar panels to get it done.My battery run is so large I will most likely have to run my generator each day for at least a two hour run to get the high current charge of 20AMPS per battery out of the way and then let the the solar panels provide the rest of the day producing the 5-6AMPS of battery charge from each solar panel and hopefully get my battery bank up to its 90% charge state then so I can do the high current battery drain that night running my appliances.My roof-top area of of OFF-RoAD POPUP will support a good 360WATTS of Solar panels and i will have two of them that will have quick disconnects so I can move to the ground and sit in the high SUN better if necessary. I will be tickled pink to be able to run my 2KW generator during the morning for a couple of hours when allowed to run them at the camp grounds and then let the SOLAR PANELs take over and get my battery banks up to at least their 90% charge state.This is how I am looking at successfully using my Generator and SOlar Panels for my off-road POPUP activities here mostly on the East Side of the US. Successful meaning I will have power all day and night to run my needs no matter what the conditions are.Roy Ken

Propane heaters that are built into the RV are very inefficient. That is why you are burning through propane. As for solar, to be close to self sufficient with solar based on your rig, will require at least 700 watts.We have total of 1000 watts, do not need to elevate. I average about 29 Amp hours from 10am to 4pm. 660 Amp hours of battery capacity. This will get my batteries back to float mode.We recently installed a Mr Heater Big Buddy. Used 3 gals of propane in 8 days. Used this to take the chill off evening and mornings. This raise the temperature from 59 to 67 degrees in 1.5 hours (early mornings). My question is what is it you really want to do? Are you trying to limit cost or just trying to limit your carbon footprint?

Solar to me is not to save money on generator gas, which is a trivial cost. Solar is what lets us stay off grid many days/weeks in a row without having to find shore power to get the batteries back to working right from doing too many 50-90s in a row. (RJ doesn't have that problem, so his reasons for solar would be different) Solar costs quite a bit so you would have to run the gen a lot for battery charging instead to pay for the solar.I don't know of a way to save on propane using solar/battery. Maybe with an electric blanket instead of the furnace so much, but not with a big electric heater instead of the furnace.Propane is only a problem if it is difficult to get a refill where you are camping off-grid. Mex complains that it costs more for gas for his truck to go get the propane miles away than the bottle of propane itself costs ISTR.Some seasonal (five month stay) campers at our summer campground arrange for a big propane tank next to their rigs and get propane delivery service for that. I find it is easy to just take a 30lb bottle to a garage for a refill every so often (costs about $29 usually)Gas for the generator is also easy for me where the gen always stays in the back of the truck so I fill the gen when I fill the truck at a gas station. It all goes on the same bill and I don't even notice how much was for the gen out of that. Not much.

Self Sufficient on Solar? Something Not Right !

40 Replies

MrWizard
Moderator
Feb 03, 2014
We have a small 200w electric heater, from lasko called a "my heat" personal space heater
designed for desk or cubicle use
October 2012 during our return from the Midwest, I would run it at night in the bedroom, outside temps in the mid 40s, draws 18~19 amps from batteries using the inverter
Since we were driving several hundred miles a day, there was no problem with the battery bank
Since then I have used it a few times to warm my desk area while on the computer late at night, but only for an hour or two
(The Oly Cat was facing the bedroom for DW),
But I could not do eight hours per night using solar only charging
pianotuna
Nomad III
Feb 03, 2014
Hi MrWizard,

Absolutely correct. I can do one night on battery electric heat if I restrict it to the bedroom and the temperature is above 0 c (32 f). Then it takes days to recharge the bank.
MrWizard
Moderator
Feb 03, 2014
RJ
I think many of the DPs have a hydro hot system burning diesel fuel for heat and hot water
A hundred gallons of diesel will go a long time with that system

Out of all the posts about solar "PT" is the only one I remember using electric heat
And his is primarily from shore power
EsoxLucius
Explorer
Feb 03, 2014
The 15,000 BTU air conditioner in my RV is also a heat pump. Hence, large battery and solar banks and a 4000 watt inverter likely would be required. Perhaps 1000AH of LifePo4 batteries at $13,000 would do the job for several hours.
pianotuna
Nomad III
Feb 03, 2014
Hi Rich,

If they have an absorption fridge chances are they are using propane for that purposed. The darn things use 4.8 kwh per day on electric.
RJsfishin
Explorer
Feb 03, 2014
OP here,
it wadnt like I was ignorant to all this inverter, battery AHs stuff,,....I guess the question really was,....how many of those big strapper solar rigs I see out in the desert here are running propane free. There just may be some.
A heat pump is probably the place to start,.....never gave that a thought.
It wouldn't be for me, but propane could be a hassle for a 45 ft MH spending 5 months out here in the desert.
MrWizard
Moderator
Feb 03, 2014
pianotuna wrote:
Hi Folks,

As a battery discharges it freezes more easily i.e. at a higher temperature.

freeze points lead acid

100% charged -67 c (-77 f)
0% charged -6.7 c (20 f)

Totally correct i said the temp backwards

i meant freezes sooner at a higher temp, not lower temp

i did say sooner, but typed lower instead of higher
free_radical
Explorer
Feb 03, 2014
RJsfishin wrote:
I'm happy w/ my small 200 watt solar, but it dawned on me the other day that if the sun hangs in here as long as I do (here in QZS) I will have saved a whole $60 of gasoline I usually burn in my Honda 1000 in a couple months. Not a terrible return on a $300+ solar investment, I thought.
But when I found myself going after my 2nd tank of propane @ 50 bucks a trip, I realized something about this self sufficient solar ain't workin quite right.
Just curious, how many are running their electric heates on some of these chilly nites,.....meaning how many more watts of solar do I need ? :)

Or maybe a better question,...how many solarers are still buyin propane. Maybe we don't have this solar all figured out yet ??

Electric heater on solar wont do it..unless the sun keeps shining 24 hrs!!

I have diesel fueled. Espar heater that uses couple gallons a week in minus 20C.
Expensive heater,but totally worth it in efficiency and low electric consumption.as
Diesel is most powerful fuel in BTU content,
pianotuna
Nomad III
Feb 02, 2014
Hi Folks,

As a battery discharges it freezes more easily i.e. at a higher temperature.

freeze points lead acid

100% charged -67 c (-77 f)
0% charged -6.7 c (20 f)
MrWizard
Moderator
Feb 02, 2014
Lesson 103 is the freezing point of a battery increases as the battery discharges.

NO..
i think you mean this
as battery discharges it WILL FREEZE at a lower temp, likely hood of freezing Increases

the freezing point is Decreased, it is Lower