How much solar to stick on a 22-24 foot "C"?

X2

Dated and some of it just plain wrong.

Boon Docker wrote:
I agree with the "Handy Bob" comment, total waste of time. Much better off to do your own research.

Lots of good info here. I am still in the process of looking for a class "C", so depending on the rig I get, I either will have two AGM batteries at minimum, or if there is more room, my ideal is three sets of two 6 volt AGM golf cart batteries, which will have plenty of power for a fridge and spinning a furnace fan.

I definitely will be using more than one MPPT charge controller. At the minimum, one for the roof, and one for the set of portable panels.

As for a furnace replacement, the ideal would be a Truma unit, but because they don't retrofit those, I may look at a vented Platinum Cat in addition to a Cheap Heat system. This way, when boondocking, heating is covered via electrical, propane, and gasoline (via the generator.)

As for wattage, I know for my use, 100 watts won't even replenish what the propane fridge consumes from its control board. 250 watts is -minimum-, but ideally, I want an order of magnitude more, which allows me to have enough power, so tossing the propane fridge is feasible.

Ctilsie242,

Start with an energy audit, or direct measurement of the energy needs.

Once again - do your energy audit.

BFL13 doesn't believe in statistics or other people experience :)... Though when dense forest is your daily scenery and the weather is 60% rain, 20% low overcast and 20% clear, I understand reluctance to plan.

There is a nice planning tool to estimate your daily solar harvest: PVWATTS calculator. Enter the watts, tilt=0 (for flat install), and you get KWH for any given month. Multiply this by 1000, divide by 30.5 days and by 13V to get daily AH. Consider that this will be an "average" daily harvest, can be 50% less on a rainy day and 50% more when it shines again, you should plan for this by either getting more battery capacity or by not taxing your solar up to its maximum output.

The only thing PVWATTS doesn't consider is shade. The OP is in Tx though.

This is one side of energy balance sheet. The other side - daily consumption - can also be planned and estimated.

Assuming that one always wants to use as much energy as possible would be wrong and not productive, leading eventually to dead end. One wants to relax, this means different things for different people. Extensive energy use is not as popular today as it used to be. Going out for a few weeks with your solar will be an ultimate test - and yes, you might have to make some corrections and adjustments to your real solar harvest numbers and the consumed energy, this could mean either adding or removing some items. RV equipment is not anything sacred, you don't have to use all of it, some things are poorly suited for offgrid living.

ctilsie242 wrote:
I either will have two AGM batteries at minimum, or if there is more room, my ideal is three sets of two 6 volt AGM golf cart batteries

There aren't too many 6V AGM, or they are expensive. There is nothing wrong with getting same bank of 12V AGM.

ctilsie242 wrote:

I may look at a vented Platinum Cat in addition to a Cheap Heat system. This way, when boondocking, heating is covered via electrical, propane, and gasoline (via the generator.)

Not sure about benefits of heating via the generator. As to the Platinum Cat, - he turned his furry tail to me and retreated when I was trying to lure him in. Small company. For almost a year the guy didn't make any units, being busy with warranty repairs, and then didn't return my email. I've bought Olympian Wave 5, works for me.

ctilsie242 wrote:

100 watts won't even replenish what the propane fridge consumes from its control board. 250 watts is -minimum-, but ideally, I want an order of magnitude more, which allows me to have enough power, so tossing the propane fridge is feasible.

At the very least, 100W will replenish that much. Propane fridge consumes less than a half of what a 100W panel would harvest on a sunny day. Don't know how tossing the propane fridge would help at this point, given a small size of solar. An order of magnitude = 10 times more, i.e. 2,500W - seems like unrealistic size for RV.

From experience, get more modules than what you think you need.

Solar energy production is a trap. After you install everything, you'll wish you had more. There is always one more thing you will wish to power, if possible.

A little birdie told me that Sam's Club has EGC2 6V batteries for $92 at this time. That is the best bang-for-the- buck out there. I have the smaller 6V's from Sams and they are doing great into year five. AGM's have there own intrinsic benefits like no acid going outside and can be installed inside the cabin. A user pays a capital expense for that design. I have both, a bank of AGM's and a bank of FLA's.

Hi,

What is a Truma unit?

ctilsie242 wrote:
As for a furnace replacement, the ideal would be a Truma unit, but because they don't retrofit those, I may look at a vented Platinum Cat

Hi,

100 watts will cover all parasitic loads and the fridge for most of the year.

I have but 256 watts of solar, and if I don't use the inverter, I run out of fresh water before I run out of power.

250 x 10 = 2500 Watts. There is not room to do that on most RV's, without going to extraordinary measures, such as putting a frame over the entire roof above any obstructions and adding drop down solar "wings".

ctilsie242 wrote:
As for wattage, I know for my use, 100 watts won't even replenish what the propane fridge consumes from its control board. 250 watts is -minimum-, but ideally, I want an order of magnitude more, which allows me to have enough power, so tossing the propane fridge is feasible.

westend wrote:
From experience, get more modules than what you think you need.

x2.
Not necessarily because solar production is a trap (I do believe than man can be in control of his habits), but because it is a lottery with chances of win varying from 30% to 90% depending on location. In some places you'll harvest enough energy (or more than enough) 9 times out of 10, in some other - one time out of 3.

I doubt that at this point - without having a rig yet - the OP will get a lot from this thread, other than ball-park estimates.

As to the portable to augment the roof solar - this is an added pain. Get a roof system as big as you can and see how it fills your needs. Then you'll know whether adding portable would help much, and what size.

Well said.

Even if the OP doesn't listen--one controller is 50% less expensive than having two controllers.

Almot wrote:
As to the portable to augment the roof solar - this is an added pain. Get a roof system as big as you can and see how it fills your needs. Then you'll know whether adding portable would help much, and what size.

It is amusing to read PT and Almot pontificating on how the way many of us do our solar is wrong, silly, or just awful. Newsflash! Other ways do work just fine thank you very much. :)

BTW, my idea of an energy audit it to actually go camping and see how that works for you and DW. Then adjust as required.