How much solar do I need?

[TexasAnnie62]

I'm wanting to go on the road but have so many unanswered questions that need to be answered.  One of them of course is how much solar do I need???  lol  I'll be working full time  and need to power a PC and two monitors for 8 to 9 hours per day, Monday thru Friday.  

Any thoughts?  Would 400W be enough?

I appreciate your input!

Annie

 

[highdesertranger]

you need to add up ALL of your power needs. phone charging, lights, fan, TV, radio, etc. you need more precise measurements of your computer. also if you are running it through an inverter you will have a 10-30% loss depending on the inverter. highdesertranger

 

[TexasAnnie62]

I have no idea how to do that.   Sounds like I should probably consult with a professional in my area.  I've watched tons of videos but can't seem to get my head wrapped around some aspects of solar.  I'm more of a mind to put as much as I can fit on my roof and hope for the best   What would I use instead of an inverter to avoid the loss? 

Thanks!
Annie

 

[highdesertranger]

"What would I use instead of an inverter to avoid the loss? "

if you want to run 120v items you need an inverter or a generator. follow these three steps we will help you out.

1. figure out daily electrical usage.
2. size the battery bank according to number 1
3. size your solar according to your battery bank.

so first lets figure out your usage most items have the consumption listed on the label. a more accurate way for 120v items is to use a Kill-a-watt meter.

if you are having a hard time list your items here and we will try to help you out.

highdesertranger

 

[Kaylee]

Are you using a laptop or desktop computer?
A laptop will be much kinder, power wise.

I use my laptop about 12 hours per day, and only have 200 watts of solar, and have had zero problems.
I do not have a fridge or any other heavy power draw.

For a laptop, I recommend a "universal laptop car charger". Check Amazon/etc, they have lots.
As well as using less power, that will be gentler on your electronics (i.e. it's DC). Inverters can be harsh on electronics, so if you do go with one, buy a better quality one. "pure sine wave" is one of the magic phrases.

Check your Library's catalog for "electricity meter". Even if your local branch doesn't have one, they probably can source one from a cooperating library in your region.
Those meters are easy to use. Just plug it in the wall, then plug your power bar with all your gear into it, and do your normal tasks for a reasonable time (at least an hour, preferably longer).
There's one or two buttons that toggle between the different things the meter measures.
Look for "watt hours".
In general, a laptop will use much less than the value on its power brick (think of that as the upper capacity of the power cord, not the "normal" use).

Also test it under the most system intensive loads you would normally do.

Since it's for your job, yes, hiring a professional is wise, however you can do the groundwork first. That'll also impress him/her.

 

[B and C]

All the electrical devices will have a label somewhere stating their power requirements.

Putting as much solar as you can fit on your roof is probably the best option with a solar charge controller big enough to handle it. Don't cheap out on the controller. Panels in a series/parallel will be the best with a MPPT controller.

Anything you can power directly from 12V would be better. Wint an inverter, you are making two changes to power. First from 12V DC to 120V AC and then the device converts that 120V AC to what it needs.

I have a HP EliteDesk 800 G1 Desktop Mini PC with a I7 processor and 8gb ram that has an external power brick like a laptop has and is the size of a paperback book. I got a car charger for it so it only has one conversion from 12V DC to 19.5V DC. Small conversion loss this way. https://support.hp.com/us-en/document/c04266271

 

[Elbear1]

I have never seen any actual tests between the inverter types (msw, psw) and inverter losses v 12v. I hear anything from 3%-20% but never actually seen it proven.

Given that even 10% loss equates to maybe $80-100 in solar vs paying 10x for native 12v appliances. 15 years ago when solar was 5x the price that made sense but when you can get 100w for under $100 those 5-10 amps you lose is not a big deal.

Its spending a dollar to save a dime

 

[Elbear1]

For example my 16" 120v fan pulls 3.24A ran off a MSW inverter with lets say 20% efficiency loss. With a 12v fan of same airflow specs I should be using 2.7A

Ran for 12hrs a day a difference of 6.5A

A 20w solar panel @ 18v x 7 hrs of sunlight = 7.77A

Quadruple the consumption and youre still talking a $60 panel. You go (re) buying monitors and fridges and fans youre spending 4 figures easy.

 

[B and C]

Not converting 12V DC is 100% efficient as there are no conversion losses. Any good inverter will post its' conversion efficiency, nothing to prove. Solar is not the only thing to consider. As the losses increase a larger battery bank is required to make up for the losses. A 10% loss takes 20% more battery (50% rule) to compensate.

 

[highdesertranger]

my Xantrex pure sine wave inverter says it's 91% efficient in the paper work. so that means you are losing 9%. this is considered a top tier inverter. I have seen reports of el cheapo modified sine wave(MSW) inverters loosing as much as 30%. my old el cheapo MSW inverter claimed a loss of close to 20% and they actually were proud of that. keep in mind this was a very old inverter.

adding solar to make up the losses is ok I guess if you have room for it. but I always say,

it is always cheaper and easier to conserve electricity than it is to make it

highdesertranger

 

[Elbear1]

9% of say 80 amps a day is 7 amps.

In reality no one builds a solar system right at bare min. A 220ah battery bank and 400w of solar wont notice 7 amps.

 

[Elbear1]

Not that efficiency is not a good thing its just 12v native costs vs solar prices (even factoring roof real estate) the economy of scale is just not there.

Not to mention replacing 12v appliances much more pricey and difficult than stopping at any walmart anywhere and getting anything you need for under $100...all for the difference of a 30w solar panel

 

[B and C]

You keep leaving out the bigger batteries needed when doing the not efficient way. The sun doesn't always shine. May work for you but I don't think I could be persuaded to haul around the extra weight too (lower gas mileage and less space). Panels are not the only variable here. Spend money on something beside a big inverter and big cables.

 

[mert3957]

I've been reading this thread for an hour and I'm lost and confused. I haven't seen the answer to what will probably be the "duh" question of the day, but how do you know how much power your stuff uses, i.e. currently have a desktop, nebulizer, immersion blender in my sticks and bricks? When I get on the road I hope to have a 12 volt refrigerator, fan and tv, if that's practical for whatever rig I end up with (it might be a tent!) Thanks for your patience with a total ignoramus when it comes to this stuff.

 

[B and C]

On your device or power brick will be where is says something like xx.x volts AC or DC and how many amps (maybe expressed in watts). On the bottom of your blender will have a label. They may not be paper and just embossed into the plastic. Failing this, the manual that came with the device will say. If that fails, the make and model number can usually be looked up online.
There are also ammeters to measure this stuff too. For 120V items, a kill-o-watt meter can be used. They make DC ammeters too. If it is a DC item that plugs into AC (power brick) it will give both the AC and the DC voltage and amps.

 

[B and C]

Here is a link to help you decipher those labels: https://www.apartmenttherapy.com/deciphering-the-power-label-on-your-ac-adapters-168405

 

[Kaylee]

The info on the power cords etc is typically the maximum used.

As Brian says, use an electricity meter (aka "kill-a-watt") to measure what each of your gadgets actually uses.

In many areas you can borrow for free an electricity meter from either your Library or local electricity provider. Check your Library's online catalog for "electricity meter". If you don't find one, call the Library and/or electricity provider.

They're insanely easy to use!
See my post on the previous page for more info.

Last year, I borrowed one, and was delighted at how much less my laptops used.
Typical tasks were less than a third of what the power cord/brick said.
Even very power intensive tasks were a little less than half.

I only measured one cooking appliance (an electric kettle), and quickly confirmed my gut impression that it would not be viable for vehicle dwelling, and bought an inexpensive non-electric kettle.

Please share your numbers!
There's Karma a plenty in doing so.
Everybody goes thru this exact same learning curve, so being confused & overwhelmed is "normal".

 

[highdesertranger]

Mert you just need to find the consumption and start adding it up. it really is simple math

I would be highly suspect of anything I couldn't find the numbers on weather it was 12v or 120v.

it never hurts to use the maximum numbers but like Kaylee said normal usage is usually much lower.

highdesertranger

 

[TMooney]

Seems to be silent disagreement on the match up of solar to batteries size combo.

 

[highdesertranger]

"Seems to be silent disagreement on the match up of solar to batteries size combo."

it's been evolving over the years. what was accepted 20 years ago is old outdated today.

highdesertranger