Posted: 11/26/2015 1:58:52 AM EDT
| I'm looking for some basic info on powering a 40ft RV or small cabin off the grid. My wife and I are thinking of moving to our remote 80ac of land and trying to get a idea of how big of a system /watts needed how many batteries we will need to power the basics, refrigerator, lights etc....Thanks for any help and pointers :) |
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RVs are very energy inefficient. They have little insulation and the AC units are sized to cool down a hot RV very quickly. This means their starting and running current draw will be larger than a high efficiency home unit, which is designed to maintain the temp in a much larger space.
Your gas heater, cook top, (maybe oven), and refrigerator will help some, but it will be largely offset by the inefficiency of your blower motor (used for heat and cooling in many RVs), water pump, lights, stereo, TV, and other stuff that is 12 volt. This may sound counter intuitive, but your solar will run a 120 volt ac inverter, which will power a 120 AV to 12 VDC converter (over sized battery charger), which then runs the 12 volt stuff. This extra conversion step will cost you 15% - 20% power loss in many cases. You can put in a 12 volt solar system, and wire the batteries directly to the RV, but it will increase your cabling cost. You will also want to change out all bulbs with LEDs, and the typical stuff like that. Instead of trying to calculate the load, get a 20 Amp, inline AC watt meter and enough adapters to plug your RV into it. These will show you max current draw and your total usage over time. Get some good measurements from your RV, while you actually use it, for a few days. (Testing in hot and cold weather is a must). You can then get the average AC and Heating hours/loading for the area you plan on living in. Beat that up against average solar charging hours in the winter and summer, along with how many DAYS of reserve batteries you want, and you will get in the ballpark...or just buy a $20K system and hope it is enough. Most folks trying to live off-grid end up with a generator and only a day or two of battery reserve. When figuring your total cost, but sure you understand the life of the batteries you are buying and realistically how often you will need to replace them. That is a major cost with Solar or wind. |
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Quoted:
RVs are very energy inefficient. They have little insulation and the AC units are sized to cool down a hot RV very quickly. This means their starting and running current draw will be larger than a high efficiency home unit, which is designed to maintain the temp in a much larger space. Your gas heater, cook top, (maybe oven), and refrigerator will help some, but it will be largely offset by the inefficiency of your blower motor (used for heat and cooling in many RVs), water pump, lights, stereo, TV, and other stuff that is 12 volt. This may sound counter intuitive, but your solar will run a 120 volt ac inverter, which will power a 120 AV to 12 VDC converter (over sized battery charger), which then runs the 12 volt stuff. This extra conversion step will cost you 15% - 20% power loss in many cases. You can put in a 12 volt solar system, and wire the batteries directly to the RV, but it will increase your cabling cost. You will also want to change out all bulbs with LEDs, and the typical stuff like that. Instead of trying to calculate the load, get a 20 Amp, inline AC watt meter and enough adapters to plug your RV into it. These will show you max current draw and your total usage over time. Get some good measurements from your RV, while you actually use it, for a few days. (Testing in hot and cold weather is a must). You can then get the average AC and Heating hours/loading for the area you plan on living in. Beat that up against average solar charging hours in the winter and summer, along with how many DAYS of reserve batteries you want, and you will get in the ballpark...or just buy a $20K system and hope it is enough. Most folks trying to live off-grid end up with a generator and only a day or two of battery reserve. When figuring your total cost, but sure you understand the life of the batteries you are buying and realistically how often you will need to replace them. That is a major cost with Solar or wind. All good advice. Off grid with all the modern convieniences will run a EASY $20k. If I were going to do it, I'd build a cabin with both solar(5kw) and at least 1kw wind. Battery bank I'd want likely 20 or more true deepcycle. I'd also INSIST on using a ammonia/propane fridge. No way I want run a fridge fulltime on solar and inverters. |
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I see you are in NV, so maybe you get more sun. I've looked at it, and if I were doing it, I would buy/make a wood gasifier generator and a tri-fuel generator and a LARGE propane tank, or multiple tanks. You can never be truly "off grid" and still have modern convinces, just un-plugged from the power grid. |