New guy here, looking for advice

[gronk]

Hey all, I'm thinking about putting solar on my rv. I have a 38' fifthwheel that I live full time in. I spend summers in Minnesota and head south in the winter (snowbird). What would be ideal in my mind is a system that allows me to not be plugged in all the time. My trailer has 50A power, but I have done just fine while on 30A. So, I have done some looking and reading and would like someone to double check my thinking. Where I am at now (Texas Gulf Coast) we are all on meters. My usage in November was 510kW. Dividing that by 31 gives me an average of about 16.5kW per day. Am I correct in thinking that translates to 137Ah per day?
What I am thinking is putting 800w of panels on the roof, making two 400w arrays to two controllers for charging and 400Ah of LiFepo battery storage along with something like a 4000w inverter to run things. Can someone please check my numbers and tell me where I am not correct?
Tom

 

[sunshine_eggo]

Hey all, I'm thinking about putting solar on my rv. I have a 38' fifthwheel that I live full time in. I spend summers in Minnesota and head south in the winter (snowbird). What would be ideal in my mind is a system that allows me to not be plugged in all the time. My trailer has 50A power, but I have done just fine while on 30A. So, I have done some looking and reading and would like someone to double check my thinking. Where I am at now (Texas Gulf Coast) we are all on meters. My usage in November was 510kW. Dividing that by 31 gives me an average of about 16.5kW per day. Am I correct in thinking that translates to 137Ah per day?
What I am thinking is putting 800w of panels on the roof, making two 400w arrays to two controllers for charging and 400Ah of LiFepo battery storage along with something like a 4000w inverter to run things. Can someone please check my numbers and tell me where I am not correct?
Tom

Units are important. When looking at energy consumption, the units are kWh or Wh. Power is Watts. That's an instantaneous rate of energy consumption.

Ah is voltage specific to relate to energy. Divide Wh by battery voltage:

16,500Wh / 12V = 1,375Ah, so I'm guessing you divided by 120V rather than 12V.

You will save a LOT of energy if you're running a propane absorption fridge on AC. They are incredbly power hungry, and a small 7.6cuft unit uses 4-5kWh/day - 1/4 to 1/3 your total consumption.

800W of solar in the winter is likely only going to produce 1.6 to 2.4kwh/day (10-15% of your daily need). You'll likely get up to 4.0kWh/day in summer (25% of your daily need).

Your 400Ah 12V battery only has 5.12kWh of energy - about 1/3 of your daily need, and you can't use any more per day than your Solar can generate.

4000W/12V/.85 (efficiency) = 392 Amps. You'll need 2X 4/0 cables between your inverter and battery.

Suggestions:
If it runs off propane, use propane.
If you need resistive electric heat, use propane.
Blanket your roof with as much solar as you can fit.
Consider 48V.

 

[gronk]

Well, shoot....... Guess I need to go back to school. The numbers I said were from the electric meter, so they should be 120v, shouldn't they? My fridge is a residential type, no propane to it at all. The water heater (6 gal) can run either 120v or propane and I already knew that it would be better on propane. So, all things considered, what should I be looking at? Unfortunately, I need to watch the cost of everything since I'm on a fixed income being retired.......

 

[sunshine_eggo]

Well, shoot....... Guess I need to go back to school. The numbers I said were from the electric meter, so they should be 120v, shouldn't they? My fridge is a residential type, no propane to it at all. The water heater (6 gal) can run either 120v or propane and I already knew that it would be better on propane. So, all things considered, what should I be looking at? Unfortunately, I need to watch the cost of everything since I'm on a fixed income being retired.......

kWh is independent of voltage. To convert to Ah, you need to divide by battery voltage. If you had a 120V battery, then yes, you would only need 137Ah of a 120V battery, but that's a whole different shit sandwich with finding 120VDC equipment.

If cost is a concern, then shore power is probably your most cost effective option. Payback period on solar is at least 3 years and usually more like 7-8 assuming you do everything yourself.

Painting with big strokes using 16kWh/day:

Need:
15kWh battery: $4500
4kW PV: $2000-4000 (probably wouldn't get you buy in Winter)
48V/6kW/AiO: $1500
Misc Stuff (wires, fuses, mounting hardware, etc.): $1000

$9,000 - $11,000

How long will it take you to spend $9,000-11,000 on shore power?

Solar almost never has a short term payback period.

 

[gronk]

kWh is independent of voltage. To convert to Ah, you need to divide by battery voltage. If you had a 120V battery, then yes, you would only need 137Ah of a 120V battery, but that's a whole different shit sandwich with finding 120VDC equipment.

If cost is a concern, then shore power is probably your most cost effective option. Payback period on solar is at least 3 years and usually more like 7-8 assuming you do everything yourself.

Painting with big strokes using 16kWh/day:

Need:
15kWh battery: $4500
4kW PV: $2000-4000 (probably wouldn't get you buy in Winter)
48V/6kW/AiO: $1500
Misc Stuff (wires, fuses, mounting hardware, etc.): $1000

$9,000 - $11,000

How long will it take you to spend $9,000-11,000 on shore power?

Solar almost never has a short term payback period.

I never expected the solar to give me much of a payback, except for spending a bunch of time not being in a campground. Maybe I just need to rethink what I want to do. Maybe get a better generator than what I have.........

 

[SamDeleted]

I never expected the solar to give me much of a payback, except for spending a bunch of time not being in a campground. Maybe I just need to rethink what I want to do. Maybe get a better generator than what I have.........

Gronk why not try start small . , just to begin with

Try off gridding one part of your life like maybe the lights or your TV .

find a cheap second hand 250W pv house panel , chuck it on the roof , get a mppt charge controller, batteries, inverter

Not sure exactly how much it would cost in the states but I could do it easy for £250 here in the UK

Make your own little solar set up... it will be good fun & a learning curve I'm sure lol !

 

[12VoltInstalls]

My thoughts are 15kWh/day must include air conditioning? Cuz that seems like a whole lot of electricity consumption for an RV. And have you calculated the meter $$/kWh? And compared that to the cost of propane?
That would give you a benchmark to decide with. If solar is only marginally more expensive in dollars you may enjoy some benefits that solar can provide.

(There’s ~92k BTUs in 1 gallon of propane and 3.4k BTUs in 1kWh)

I live in an offgrid 24’ camper with mods for winter use, a 800W solar power system, and have a 120V fridge. I use 1/5 to 1/10th of your kWh.

Anyways, depending on your meter charges- or maybe notwithstanding your meter charges- payback on solar (as mentioned above) may not be a near-term reality. But as a convenience expense may still be worth it to be more autonomous while traveling or have some intermediate travel options you don’t really enjoy right now. But I’d see how to cut consumption a bit.

Iirc there’s several places from Georgia to Texas where you can buy 2nd life solar panels inexpensively if you pick them up. Like $650- $1000 for 8 to 10 300W panels.
Then an inverter charger and an mppt, or an AIO and you are in business except for the most expensive part: a battery. But you could DIY that or buy budget lithium batteries and still possibly land below $4000. If your metered electric is $40/mo that’s ~8+ years to break even at months extrapolated but you are only probs 4-6 months a year in the gulf.
But you’ll have to figure out how to miser down the electric consumption a bit.

 

[gronk]

My thoughts are 15kWh/day must include air conditioning? Cuz that seems like a whole lot of electricity consumption for an RV. And have you calculated the meter $$/kWh? And compared that to the cost of propane?
That would give you a benchmark to decide with. If solar is only marginally more expensive in dollars you may enjoy some benefits that solar can provide.

(There’s ~92k BTUs in 1 gallon of propane and 3.4k BTUs in 1kWh)

I live in an offgrid 24’ camper with mods for winter use, a 800W solar power system, and have a 120V fridge. I use 1/5 to 1/10th of your kWh.

Anyways, depending on your meter charges- or maybe notwithstanding your meter charges- payback on solar (as mentioned above) may not be a near-term reality. But as a convenience expense may still be worth it to be more autonomous while traveling or have some intermediate travel options you don’t really enjoy right now. But I’d see how to cut consumption a bit.

Iirc there’s several places from Georgia to Texas where you can buy 2nd life solar panels inexpensively if you pick them up. Like $650- $1000 for 8 to 10 300W panels.
Then an inverter charger and an mppt, or an AIO and you are in business except for the most expensive part: a battery. But you could DIY that or buy budget lithium batteries and still possibly land below $4000. If your metered electric is $40/mo that’s ~8+ years to break even at months extrapolated but you are only probs 4-6 months a year in the gulf.
But you’ll have to figure out how to miser down the electric consumption a bit.

Yes, the power consumption includes A/C, sometimes even both of them. It also includes a 1300w resistance heater, and also the element in the water heater. I know there are lots of ways to cut back on consumption, but used those numbers because that is what I have to work with and I would rather err on excess rather than not enough.
edit: my electric was $63 last month

 

[Sojourner1]

@gronk just for reference what might be possible with solar production and this is 1,280w. I live fulltime in my 5th wheel and 99% of the time boondocking with Nov 5, 2021 was our last hookup passing through CO. We don't have a residential fridge. Here are some total monthly production # for the past 3 years (I have #s going back to 2017). You're better off just plugging in unless you're truely committed to staying off grid for it really pay off financially.

 

[sunshine_eggo]

I never expected the solar to give me much of a payback, except for spending a bunch of time not being in a campground. Maybe I just need to rethink what I want to do. Maybe get a better generator than what I have.........

Take a look around at the things you NEED to run off-grid and conduct an energy audit:

System Energy Audit and Sizing Spread Sheet

To get the spreadsheet, click on the orange button at the top of this page. This sheet is intended to help you plan your system. Fill it out down to the last decimal place, look at the results..... and then make your best guess;) Notes...

diysolarforum.com

 

[SamDeleted]

@gronk just for reference what might be possible with solar production and this is 1,280w. I live fulltime in my 5th wheel and 99% of the time boondocking with Nov 5, 2021 was our last hookup passing through CO. We don't have a residential fridge. Here are some total monthly production # for the past 3 years (I have #s going back to 2017). You're better off just plugging in unless you're truely committed to staying off grid for it really pay off financially.

View attachment 125383

It's funny your production doesnt change much summer Vs winter , you must be in a southern climate ?

 

[Sojourner1]

We travel in the west head northerly more or less for spring, summer, fall (NV, UT, CO, WY, ID, SD, ND, NE, MN, KS, OK, TX, NM) and south for winter (AZ). Just depends what we feel like seeing or doing.

 

[kbeefy]

I never expected the solar to give me much of a payback, except for spending a bunch of time not being in a campground. Maybe I just need to rethink what I want to do..........

Something to consider.... You list AC and resistive heating as 2 large energy uses. Your snow-birding, living in a home with wheels. You want to spend time boondocking (not in a campground).

Getting rid of AC is huge. Using propane for heating is huge. Ambient temps are the biggest hurdle to overcome, always.

1- If your trips between MN and the Gulf are slower, you will use much less AC and heat. chase the endless summer, follow that perfect fall day!
My main climate conditioning is done with the steering wheel.

2- Simplify, get rid of some of those shore power loads. Almost everything will run off DC these days. Or at least there is an alternative that will.

If you can't do this, then you need to continue to be hooked up to the grid. Nothing wrong with that, as long as the grid is there.
Any other option is going to be too expensive.

 

[gronk]

OK, you guys have convinced me that my dream is just that........ a dream. Since it would be so expensive for me to go solar and given the fact I'm not exactly a "spring chicken" (I'm 67), I guess I am better off staying as things are. Thanks everyone for the assistance!

 

[GooseF16]

ha.. we get it.. the AC and any major resistive loads consume most of your energy in comparison.. but it is nice to have a good robust battery system that can boondock without shore power if not running the AC much.. and put stuff on 12v or 24v.. for example, a NOrcold DC fridge is much more efficient. LED lighting, that you can select on/off, and an efficient heater.. the forced air blower setups are effective but even the 12v motor is a hog.. I recently got a coach with the trumA system.. very efficient propane/dc system, and a propane demand hot water system.. so aside from the Air conditioner, the coach doesn't pull alot of power and teh 400 watt solar keeps up no problem.. But fire up the AC, and thats a whole diff story.. If I had a traditional coach, or trailer, I would still want an onboard generator, unless I installed a robust system using a terroidial LF unit like victron to regulate my shore power input and supplement.. such as tHe multiplex.. When going with a split phase, that opens up another level of complexity that needs addressed on solar tho.. but there is alot of experience on here.. these people know their stuff on here.. good luck.. I know of a few folks that specialize in RV installs tho.. maybe one will chime in here.. I know a specialist installer/designer in Arizona if you wanted to PM me.. you have to go to him though.. He says to get a system that can run AC for periods of time, be prepared to spend 12 to 15k for a total system remake. for example.. that would be something like 1400 watts solar, 24v, 10kw, Victron components, and retain full 12v use of system via step-down, and trickle charge AGM starter batt on genny. dont hold me to money but thats probably a good guess

 

[gronk]

Well, I knew the electric heat and the AC were big hogs of power, but I did say that I can do without them PLUS the 15oow electric element for the water, so I am thinking that I would be looking at half if not less KwH, but I do have a residential fridge. I am probably just going replace my 15yr old genny for a 4500w inverter type since my old one has such dirty power. Digital clocks go nuts on it!

 

[sunshine_eggo]

Well, I knew the electric heat and the AC were big hogs of power, but I did say that I can do without them PLUS the 15oow electric element for the water, so I am thinking that I would be looking at half if not less KwH, but I do have a residential fridge. I am probably just going replace my 15yr old genny for a 4500w inverter type since my old one has such dirty power. Digital clocks go nuts on it!

If your only major AC appliance is a compressor fridge, the numbers get much more manageable.

Consider doing an energy audit as I recommended above.