How to measure how much solar we need?

[path1]

(hope this is right section) Brought home TT last month and now have basics taken care of and RV is road ready. Now starting to think about bigger long term projects.

One project is, we would like to get some solar. Which I know nothing about. I suspect the first step is figuring out a starting place for this project. So I'm assuming that finding how much we actually need might be a good starting spot.

Is there any meter or way to measure to figure out what we need? I'm thinking, if we know how much we use, we could determine how big or small of solar project would be. Thinking in my mind about some type of elec meter that we see how much we use in a week.

Or maybe better yet; how did you figure out how much solar you needed?

Anybody care to pass on any good links or info on RV solar?


Thanks

[BFL13]

jrnymn7 wrote:
Realistically, how much more solar does one need for a flat install, vs. tracking? 5X, 10X, ??

You have to say when and where. The higher the sun (daily and seasonally), the less difference between flat and tilted. You can't average it in any useful way either. You get what you get.

Repeat- at 49.3N in May, for 130w it was 56AH flat vs 70AH tilted, vs 90AH tracking. For 280W at 49.3N in May just do 280/130 times those, it is all proportionate.

So you can do the math to answer the burning question. In my case there, at that time and place, how much flat would do that 90AH same as tracking with the one 130w panel?

90/56 x 130 = 209w flat

It won't come out the same in Arizona in February

[RJsfishin]

jrnymn7 wrote:
Realistically, how much more solar does one need for a flat install, vs. tracking? 5X, 10X, ??

I'd guess it at double, w/ a lot of variables.
I had 200 watts tracking, and it was all of enuff.
Now I went flat....tiltable, and added a panel....300 watts total.
I'm hoping the 300 flat tiltable, will do what the 200 tracking did.
Will know more about it when I get to AZ for the winter.

[jrnymn7]

Realistically, how much more solar does one need for a flat install, vs. tracking? 5X, 10X, ??

[JiminDenver]

MrWizard wrote:

Never have I read about an RV`r saying they got 600 amp hrs in a day
I think you have a typo confusing watt hrs and amp hrs
600 amp Hrs would be way over 7000 watt Hrs...approx 8000 watt Hrs

I looked, a amp hour is the same now as it was 35 years ago. use one ampere for one hour and it is one amp hour. 50a for one hour is 50 Ah. 50a for 12 hours is 600 Ah.

I designed our system to be able to run a small air conditioner without draining the battery. I'm looking into options for the power that isn't being used.

[Almot]

Canadian Rainbirds wrote:
My solar, 420 Watts, and 484 AH of battery is almost enough for the winter in Mexico (without AC) and the same up here in the summer if we're not under the trees.

Yep. Minimum 500W for winter in Mexico or summer in BC-WA. Make it 700-1000W to be able to camp in partial shade too.

Winter in WA, on solar, jeez... I can survive on zero watts when it's warm and dry in daytime. When it's 40F in the night AND in the day and rains non-stop for a week - I wouldn't even try living without 110V grid, or a wood burning stove, or a generator.

[Canadian_Rainbi]

How much solar do you need? More than you have room for! It will never be enough--it's like a boat or an RV. Always need just a little more.

Like BLF I too live on Vancouver Island. My solar, 420 Watts, and 484 AH of battery is almost enough for the winter in Mexico (without AC) and the same up here in the summer if we're not under the trees.

On a day like today I consider installing rain gutters and a downspout with a water turbine on the end.

[Almot]

path1 wrote:

I'm starting to read some of the links people have posted and starting to believe solar is like tire posts. What works for some doesn't mean it will work for you.

Maybe my question should of been, how much solar do you have and do you like it?

No. Links by Pianotuna to system sizing/estimates and general solar info are not lifestyle-specific. Your initial question was right, but there is no answer when there is no input data.

You asked about winter in your area. 1000W flat solar in Seattle in December will collect on the average 28 AH a day. I don't know how much the system will collect on (very typical) rainy day there when it rains all day long. Possibly 5 or 6 AH, just enough to compensate parasitic currents like LP/Co detectors and battery self-discharge. Nothing else, no loads at all. On a good day in December it will make probably 60-70, but in this area in December there can be one good day per 7 bad days, and it's not a good idea letting batteries slide towards 50% for 6 days (even if your bank is so huge that you can stretch it for 6 days).

In other words, with energy needs that you described - btw, they look like modest to me - I agree with BFL, which is something that I don't do very often :). There is almost zero sense in getting solar for coastal WA winter. Your will be able to live without generator on dry days only, AND if you max up the solar watts. On cloudy and half-wet days you could live off 1000W solar only you minimize your energy consumption as much as possible, because you will only get ~30 AH and this is only enough for lights, some heat, and very little TV time. No microwave, no hair drier, no any 110V devices.

In summer it's better, I would say you could live off 1000W there. For going South in winter, you won't have problems living on 700-800W.

How much watts people have and like it? 500W allows me living generator-free in winter in Mexico or in summer in areas like yours, though my energy needs are less than yours. Smkettner is making it on 700W in Ca, also generator-free, and I think he likes it. There is only one item that you can't have on solar under the best weather conditions - air conditioner. Pianotuna is planning to have this too, but here is "cheating" ;), charging battery while driving his motorhome and not running A/C in the night.

My numbers for Wa winter are based on flat panel. Tracking or tilting big 700W or 100W array is a royal pain. People do this with portable setup, but this is a different creature and pain of a different kind.

[jrnymn7]

During winter, I'll be happy if my two 140 watters replace any continuous draws, like the fridge and heating. Anything over that should easily be handled by two hours of gen time, every other day.

During summer, I suspect 280w will be more than sufficient for my needs, unless I run the a/c for prolonged periods.

I'm thinking in the OP's case, two (portable) 230w 24v panels would be a really good start, provided he can handle the sluggin' involved to set up and tear down, and he gets his usage under control; especially the furnace draw.

I'm usually on the move, on a daily basis, but if I were parked for a week or more at a time, I wouldn't hesitate to go with bigger (heavier) panels, and track the sun by repositioning them two or three times a day.

[pianotuna]

Hi,

Solar is also for maintenance charging in storage. I get about 17 amp-hours on December 21. That's more than enough to keep the battery bank happy.

If I quintuple my system, I'd get enough to run the furnace on a 25% duty cycle, year round. I'd also have enough to run the fridge for over half the year and in the hot summer months I might just be able to run the air conditioner (but not much else).

[BFL13]

We live in BC, not the PNW, but have similar conditions on the Island to what they get in the PNW.

For camping in the provincial parks here (sites are in the woods)solar is totally useless. We only use the solar when camping off grid out in the open in summer.

To get by off grid in the woods, no solar, it is all about generator and charger and batteries. We do not go without comforts either. Have a 2000w inverter to run the microwave, kettle, toaster, etc.

In 35F temps in February short days, lots of furnace time, daily AH can be near 200AH, half that being furnace, so that is a recharge every day with a 460AH bank.

I can recharge the battery bank from 50% to 90% in the two hour window the parks give from 9-11am in the morning (we don't run the gen for the 6-8pm window) because we have a Honda 3000 that can run 130 amps of charging.

So if you want your comforts, you have to be prepared. If you don't have enough charger or generator or battery, you have to cut back on the comforts.

IMO, unless you are camping out in the open in winter there is no point having any solar at all. Even if you do have "some" the weather is against you and the days are too short to get anything done anyway.

Solar is for summer out in the open or winter down South in the open.

[pianotuna]

Hi,

I love solar and have been using it for 15 years. Before I moved to full time I managed to go for about 5 years with no generator.

I'm considering quintupling the watts I have. That should nearly eliminate all generator use, including running the fridge in the summer time.

path1 wrote:
Maybe my question should of been, how much solar do you have and do you like it? Thanks

[path1]

NinerBikes wrote:

OP needs to tell us more about the rig he is in, what they use that sucks power, and wifey habits. Obviously, hair dryers, and A/C's and microwaves may be out of the picture, without a generator if in a smaller rig.

OP here....More info if it will help.

We just brought wives TT home last month. We have RV'd for many years and have had several RV's (actually too many). The latest is a 2013 Arctic Fox that and it is the wives. We love to travel in our X-rental Majestic that replaced our 37ft 5th wheel six years ago and will keep it. The places a small class C can get into are great. But as about everything else in RVing there are compromises. One of the compromises is the size of RV. Small class C is great for shorter amount of time, but when its raining or staying put for longer time, they are not so good for us!.

We wanted something that we would be more comfortable for staying put for longer time and more room especially in the kitchen area. Overall be more comfortable.

Talking with people that do have solar we've noticed that some people want to power a small city and others say they should of put up more.

Being we seem to blast thru batteries, we thought why not get some solar? Most of our camping trips are in the winter time the temps are in the 30-40's and raining. But our lack of sun in the pacific NW we'll probably need more than the usual. We are going to start our "going south" again to warmer climate as soon as wife gets OK from her Dr.

So knowing nothing about solar, I thought others might chime in and atleast get us going in right direction. Our elec usage IMO is "normal" we like temps 70-72 degrees and wife will read 1/2 the night with some lights on. IMO wife is not as conservative as she should be, but that's OK, she thinks we'd get better MPG if I didn't bring so many tools and spare parts along. But she doesn't complain about my shop labor rate when something needs fixing and I don't complain about all the gadgets or weight of them in the kitchen. So I guess we're even.:B

Our generator is an old Honda (1990's model)that is not so quiet compared to newer light weight ones, so we don't use it if we think it will disturb others. And I thought we might be able to leave generator at home with enough solar being tow rig is an older diesel. That would be no gas and gas cans.

I'm starting to read some of the links people have posted and starting to believe solar is like tire posts. What works for some doesn't mean it will work for you.

Maybe my question should of been, how much solar do you have and do you like it?

Thanks

[NinerBikes]

Yes, 50 Amp hours for the day, more than enough for a little 21 foot travel trailer. My 120w Solar panel makes an easy 6.3 to 6.6 AH for 8 to 10 hours in MT that time of year.

I don't sit in the TT all day, when fly fishing or near Yellowstone National Park... so when sight seeing, it's a good thing the days are long.

MrWizard wrote:
Niner...do you mean 50amp Hrs ? Total for the day

NinerBikes wrote:

RJsfishin wrote:
Thinking in terms of "reality", I love your wording, "possible" 52 amps
But then, I love the 14 hr days too:B.

I saw, for real, a 50 amp day on my 120W portable solar panel. It was June 10th, and I was camping in Montana on the Madison River. I had to leave my bathroom fan on all day, just to make it possible, but, past May through August, if you camp in northern latitudes in the summer, on a sunny day, it can happen with portable aimed panels moved 3x a day.

OP needs to tell us more about the rig he is in, what they use that sucks power, and wifey habits. Obviously, hair dryers, and A/C's and microwaves may be out of the picture, without a generator if in a smaller rig.

[MrWizard]

Niner...do you mean 50amp Hrs ? Total for the day

NinerBikes wrote:

RJsfishin wrote:
Thinking in terms of "reality", I love your wording, "possible" 52 amps
But then, I love the 14 hr days too:B.

I saw, for real, a 50 amp day on my 120W portable solar panel. It was June 10th, and I was camping in Montana on the Madison River. I had to leave my bathroom fan on all day, just to make it possible, but, past May through August, if you camp in northern latitudes in the summer, on a sunny day, it can happen with portable aimed panels moved 3x a day.

OP needs to tell us more about the rig he is in, what they use that sucks power, and wifey habits. Obviously, hair dryers, and A/C's and microwaves may be out of the picture, without a generator if in a smaller rig.

[MrWizard]

RJsfishin wrote:

Quote:
the 5-600 AH the panels can do tracking on a good summer day
--------------------------------------------------------------
How does one do this w/ 700 watts of panels ?
My 100 watt panels put out 5 amps max while tracking on a good day.
7 panels x 5 amps = 35 amps max.
35 amps x 8 hrs = 280 - 300 AHs per day,.....a very far cry from 5 - 600.

Where did I go wrong ?

I have 505 watts of panels
This time of year I avg 60+ amp Hrs.....aka 840+ watt hrs
The max charge I have ever received was just over 2000 watt hrs in July on the coast
Never have I read about an RV`r saying they got 600 amp hrs in a day
I think you have a typo confusing watt hrs and amp hrs
600 amp Hrs would be way over 7000 watt Hrs...approx 8000 watt Hrs