12v, 24v, or 48v?

[wpns]

Thanks for all the information, a trove of ideas. I should have mentioned I'm in the USA, Southern California. My house is 100+ years old, small, and I'm not sure the roof would support solar panels. It looks like a power audit is my first move...and could someone define "constant load" for me. If it's what it sounds like, then the only thing I have that's constantly on is my computer, router, and modem. The refrigerator is off and on, does that count as constant load?

Your best bet is to know for sure what your typical day profile looks like, here's mine:

You can see it never gets below probably 1500 watts, so that's my baseline. It averages 2430 watts and peaks over 7000 watts (clothes dryer, hot water heater, kitchen appliances). [Ignore the details, this is an example, we use a crazy amount of power, mostly because it's 'free'.]
So now I know (for this day), what my inverter size needs to be (8KW minimum), what my battery size needs to be (60 KWHR*), and that I need 12KW of solar panels (60 KWHR divided by my average 5.2 peak hours of daily sunlight).

How you get the above is up to you, mine is bespoke from some esoteric hardware, but I've been doing this for a long time. Sense or other cheap monitors can give you a rough idea of your daily profile, and then you can confirm with your power bill (which will tell you how many KWHR you use in a month, divide by 31.25 to get your daily _AVERAGE_. You can get a clamp-on ammeter, turn on every appliance in the house, and read peak amps and guess at peak power.

Don't forget to round up and add more of the cheap stuff. Panels are cheap, max out your roof or ground mount, too much power production is a good problem to have. Batteries are expensive, though coming down in price, so buy (or build, see the whole forum topic on DIY batteries if you are so inclined) an expandable system that you can add onto later. Likewise, get an inverter that you can parallel later if you decide an all-electric kitchen is 'best' for you.

If the costs start to get out of control, add a small backup generator into the mix, 4 days of battery will cost a lot more than a small Honda inverter generator (to say nothing of the other cheaper brands out there) and a few gallons of gasoline. The Honda EU2200 for instance will run 3.2 hours on 0.95 gallons of gas and make 5760 WH of power in that time to charge up your batteries, which trades off $1500 worth of batteries for a gallon of gasoline and a $1K generator.

(*) Yeah, the battery size can be reduced to 'what I need to get through the night', especially if I do some load shifting (laundry during the day), but should probably be upsized to handle multiple dark days.

Your Milage Will Vary, but it all starts with an audit.

 

[CaliSunHarvester]

The refrigerator is off and on, does that count as constant load?

It does pull energy constantly but at varying rate. For the fridge , i would plug it into a kill-a-watt type plug to measure consumption over a week. That tool costs about $15

 

[50ShadesOfDirt]

We run our entire home from 24v, using a tier-1 magnum inverter/charger ... never had an issue with cabling, battery-bank (now at 2s2p 12v300ah), or anything else. Using tier-1 equipment from 5+ years ago, we probably saved some initial money. 24v isn't bad at all, and we run a family of 4 and a 1000sf home chock full of electrical crap with no problems, so it can be done.

A bigger q is tier-1 LF vs AIO (hf or possibly lf mixed in). Search through this forum to see all kinds of threads for related issues, where folks were down for days/weeks because the AIO is giving grief, whereas the LF keeps going strong ...

Pay attention to overall design, and reduce before designing gear to meet the loads.

Buy from CurrentConnected or similar, and avoid those sellers/products where SALES, not service, seems to be the focus. Threads abound here as well ...

More importantly, one point I consider important in a "system" providing power to you (and thus critical) is to have fallbacks built into the system at various points. If you are 48v, don't start out with just one "server battery", which becomes a SPoF. Get at least two, because you can fall back to one, if the other is giving grief. If you are AIO, perhaps build two into the system, or have one on the shelf, for fallback. Again, search forums for related threads ... avoid spof's.

Have a gen somewhere in the system.

Hope this helps ...

 

[new off grid]

As a solar novice I need to decide on the voltage of my system. I'm not sure what the advantages and disadvantages are of the different choices. Why is 12v better or worse than 24v or 48v? In my case, I want to start out with a portable system to deal with power outages (I'm in a brush fire area), but I want to be able to expand it later on. Initially I need to be able to run my refrigerator(full load amps: 6.5a, a few lights, my desktop computer with a router and modem, a small laser printer. Also a 1250 watt electric frying pan. The power outages usually last from 1-4 days.

Advice and suggestions would be welcomed...

48 is the only way to go when build a new system
unless for a small, sub 500w

 

[Rednecktek]

48 is the only way to go when build a new system
unless for a small, sub 500w

Or if you have a lot of heavy 12v loads already and only need 1-2Kw of AC power.