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Old 09-02-2019, 10:49 AM   #1
Skoolie
 
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Show me your electrical budget?

Trying to figure out my electrical budget... Kinda hard to estimate sometimes because appliances aren't listed with useful consumption statistics. Would be very helpful to steal some numbers.... Anyone want to post their numbers?

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Old 09-02-2019, 10:59 AM   #2
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If you want to nail the numbers with good accuracy get a Kill-A-Watt meter and measure the actual consumption in real life conditions.

https://www.amazon.com/P3-Internatio...ateway&sr=8-18

With a bit of creativity the SC-2030 battery monitor has worked for me to log DC consumption over time and document my DC loads.

http://www.bogartengineering.com/pro...rimetrics.html

Good move figuring out your loads as your first step in electrical design.

I see way too many folks show up on the solar forums asking "I bought all of this stuff..... Can someone please tell me how to make it run my house/RV?".

Determine the loads you need to support.

Size a battery bank to support your loads.

Size your solar system to meet your batteries needs.
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Old 09-02-2019, 11:02 AM   #3
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Originally Posted by PNW_Steve View Post
If you want to nail the numbers with good accuracy get a Kill-A-Watt meter and measure the actual consumption in real life conditions.

https://www.amazon.com/P3-Internatio...ateway&sr=8-18
This is a problem when trying to decide what appliances to purchase. It's also not always easy to find the numbers we need listed on the product. You can buy all you products , then decide what you need to run it all, or have a system that the new products will work with.
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Old 09-02-2019, 11:48 AM   #4
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I don't know how much use other people's figures are going to be for you.

I second PNW_Steve's advice on the kilowatt meter for things you already own (as well as everything else. Great advice.). It was a great help figuring out stuff that varies in power consumption as it runs, or that tells you more what it can supply than what it actually does. In particular, anything that charges a DC battery (cell phones / tablets / laptops), and anything else on a wall wart.

Refrigerators... very likely you don't have that in front of you at the moment, so if can't hook a meter up to it, I've just assumed a 50% duty cycle. That's probably a liberal estimate, which is what I make every estimate... liberal. Same for water pumps, AC, etc... anything with a duty cycle, hooked to a thermostat, etc. Sometimes you just gotta go with an educated guess. The more educated the better, but err high.

Electronics can vary greatly depending on make & model. If at all possible figure out the actual item you want, and then use the numbers listed in the product manual or product specs (you can almost always find these figures online these days). I was amazed at the differences in power consumption, for example, between two different monitors of exactly the same size and display type (those were measured). For the same reason, pay a lot of attention to the power specs of the items you're considering for use in your bus. Being choosy can yield big dividends when running off solar.

I've found most appliances that heat elements or run motors to be pretty much spot-on with their documented specs. Same with lighting... I wouldn't even bother measuring it.

One thing you have to watch out for are vampire loads. That's another great use of the kilowatt meter. If in doubt... you can always control such items with a switch so they're really off when they're off.


One more thing... if you do an internet search, you can find multiple listings of power consumption specs for household items. From my comparisons with measured (& documented) items, I wouldn't trust any of them.
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Old 09-02-2019, 12:41 PM   #5
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I don't know how much use other people's figures are going to be for you.

I second PNW_Steve's advice on the kilowatt meter for things you already own (as well as everything else. Great advice.). It was a great help figuring out stuff that varies in power consumption as it runs, or that tells you more what it can supply than what it actually does. In particular, anything that charges a DC battery (cell phones / tablets / laptops), and anything else on a wall wart.

Refrigerators... very likely you don't have that in front of you at the moment, so if can't hook a meter up to it, I've just assumed a 50% duty cycle. That's probably a liberal estimate, which is what I make every estimate... liberal. Same for water pumps, AC, etc... anything with a duty cycle, hooked to a thermostat, etc. Sometimes you just gotta go with an educated guess. The more educated the better, but err high.

Electronics can vary greatly depending on make & model. If at all possible figure out the actual item you want, and then use the numbers listed in the product manual or product specs (you can almost always find these figures online these days). I was amazed at the differences in power consumption, for example, between two different monitors of exactly the same size and display type (those were measured). For the same reason, pay a lot of attention to the power specs of the items you're considering for use in your bus. Being choosy can yield big dividends when running off solar.

I've found most appliances that heat elements or run motors to be pretty much spot-on with their documented specs. Same with lighting... I wouldn't even bother measuring it.

One thing you have to watch out for are vampire loads. That's another great use of the kilowatt meter. If in doubt... you can always control such items with a switch so they're really off when they're off.


One more thing... if you do an internet search, you can find multiple listings of power consumption specs for household items. From my comparisons with measured (& documented) items, I wouldn't trust any of them.
Good points.

I have found USB charging outlets, water pump and LED lights that will all run native from my 24v house battery.

All of my 110v electronics will be on switched circuits to eliminate Vampire loads.

I am a geek and measured my lights too...
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Old 09-02-2019, 01:04 PM   #6
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Originally Posted by PNW_Steve View Post
Good points.

I have found USB charging outlets, water pump and LED lights that will all run native from my 24v house battery.

All of my 110v electronics will be on switched circuits to eliminate Vampire loads.

I am a geek and measured my lights too...

Any chance you could link to the lights you found, and if in service, your impressions of them? I've been having a hard time finding a lot of selection in 24V. Was considering wiring 12Vs in series, but I'd rather not. Same with the USB outlets, any info would be awesome. Water pump was easy. Still up in the air on 12 vs 24... on right on the edge where one makes sense over the other.

So... how close were your lights to their documented draw? (I would have too lol. I just don't have any to measure yet )
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Old 09-02-2019, 01:17 PM   #7
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So I am fully aware that the numbers can vary wildly, but the first step in estimating something is knowing what a good estimate might look like - thus my request.I'm not as worried about the specific values as the orders of magnitude. It's also hard to estimate electric needs for things I don't own: appliances, minisplit, water pump, etc.
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Old 09-02-2019, 04:45 PM   #8
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Just finished a revamp of my electrical cabinet today. The way I sized my (solar) system, I first looked up estimates on how much each appliance I wanted to run in wattage + duty cycle in a day. Not the specific make/model, I looked for averages. In the end, I had a list like this:



  • 110VAC, 220VAC Residential dryer: 1800W-4000W, 30mins-2hrs
  • 220VAC Mini split: Varies, 19 SEER 12000BTU: 1050W, 37 SEER 9000 BTU: 500W, 6-8hrs
  • 12V chest fridge: 40W-100W, 6hrs
The list doesn't need to go on, really. The rest of my appliances sip juice, not gulp it. At those ratings, I'm looking at between 2kWh-5kWh per laundry load, 6kWh for the mini split, and 1kWh for my two fridges. Overall it seems reasonable I'd use between 5 and 11kWh per day, depending on laundry. (I need to test my washer/dryer combo, needed to rebuild my cabinet and hook up water, so we'll see about that later this week).




For solar input, I have a hodgepodge 700W of mixed panels I've been playing with. Those panels yield around 2100Wh per day on average, or 3x its size in Wh... so that is the model I went with after monitoring generation over a long period of time. This meant I needed around 1800W - 2200W to start with so I could get around 6kWh generation, maybe 8 on a good day out in the open.


For batteries, I looked around for the biggest bang-for-buck in lithium. My research found this to be used 5.3kWh Tesla packs. Maybe there's a better Wh/$ combo, I haven't seen it. Each pack goes for around $1300 on Ebay, and I wanted three to start because in reality, my usage might actually be as low as 1kWh-2kWh if I'm not pumping AC or doing lots of laundry.



My costs?

2200W panels ($2300) + batteries ($4000) + charge controller (Victron Energy 150V/100A: $800) + inverter (PowerJack Split Phase LF 8000W, $450) $7550. Then there's at least another $500 in outlets, conduit and AC wire, $1500 of big fat battery wires, connectors, breakers, fuse panels, bus bars, etc. Part of my revamp involved adding a 1000A negative bus bar (I was using a pair of 250A on negative, 1000A on positive), changing to 4/0 wire to the inverter and 2AWG to each battery. Cha-ching! And a royal pain in the backside crimping on those giant connectors!



TL;DR: It gets really expensive if you want a big system that does it all. Arguably not worth it, I just didn't like the idea of switching between shore, solar, and a genny. I wanted a universal solution done right and sized for my needs, and I intend for it to last me a while. There are plenty of folks out there with 400W of panels and a single or couple 12V 100Ah batteries that are churning along just fine. I wanted the energy experience of a common household but on wheels, I did the research to support it and paid the money to build it. And I enjoyed doing it. The little guy doing his thing with a couple panels and a goal zero, he's no worse off if he's meeting his needs. Find yours.
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Old 09-02-2019, 05:20 PM   #9
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Originally Posted by TheHubbardBus View Post
Any chance you could link to the lights you found, and if in service, your impressions of them? I've been having a hard time finding a lot of selection in 24V. Was considering wiring 12Vs in series, but I'd rather not. Same with the USB outlets, any info would be awesome. Water pump was easy. Still up in the air on 12 vs 24... on right on the edge where one makes sense over the other.

So... how close were your lights to their documented draw? (I would have too lol. I just don't have any to measure yet )
The USB ports and the water pump were easy. The lights are pairs of 12v led lights in series.

https://www.ebay.com/itm/12-24V-Car-...ss!99328!US!-1
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