8,192 posts, read 23,724,630 times 3,040 posts, read 8,930,309 times Originally Posted by Racelady88 115V x 15A = 1725 Watts Due to inrush (starting) current, you will want to go at least 25% bigger. I would recommend one even larger than that, probably something around 3000 Watts, though you could probably get by with 2500 Watts. These are for peak load ratings. Sustained load ratings should be around 2000 Watts. Don't forget that with a window type A/C unit, you will need to mount the shell of the unit outside the van for proper venting of the hot exhaust air. This will most likely need to be out the rear of the vehicle so it doesn't protrude beyond the sides of the vehicle into an adjacent lane. Also keep in mind that if the inverter is being run off the starting battery that it wouldn't take long for the battery to drain to the point where the vehicle won't start. You will most likely want to be sure that there is a separate battery for the inverter, and that it is isolated from the starting battery so the ability to start the vehicle isn't compromised.

You'll also want to be sure that the vehicle's charging system is adequate. Also remember that in order to keep the batteries charged in the vehicle, the engine will need to be run long enough to recharge them. 4,515 posts, read 17,060,880 times Originally Posted by jdavid93225This is what I needed to know. I have a brand new deep cycle RV/Marine battery to push the inverter. The unit is going to take the place of one of the rear windows. He is going to be so excited to have A/C. 3,460 posts, read 3,731,105 times 1800 Watts at 12 volts would be 150 Amp draw on the alternator/battery....ouch I'd look at one of the RV units runner mentioned. They should already be set up to run on 12 volts. A ROOM AIR CONDITIONER WILL ONLY WORK FOR ABOUT 20 MINUTES OR LESS ON BATTERY POWER FROM TWO BATTERIES. A single battery might not even provide the amperage to start the AC after the first couple uses. Boy times have really changed... When I bought my Statpower 1500 I paid almost a $1 a watt all those years ago...

If you are really serious about finding the most efficient A/C... you need to look at some of the marine units... start at a place like West Marine... I think they have several offerings in the Master Catalog...units of hvac What Exactly Does the Wattage Rating on a Power Supply Unit Mean?air conditioner outside unit running Your PSU is rated 80 Plus Bronze and for 650 watts, but what exactly does that mean? gas heater and ac unitRead on to see how wattage and power efficiency ratings translate to real world use. Today’s Question & Answer session comes to us courtesy of SuperUser—a subdivision of Stack Exchange, a community-drive grouping of Q&A web sites. SuperUser reader TK Kocheran is curious about power supplies: If I have a system running at ~500W of power draw, will there be any tangible difference in the outlet wattage draw between a 1200W power supply vs, say, a a 800W power supply?

Does the wattage only imply the max available wattage to the system? What is the difference? And what, for that matter, do the 80 Plus designations mean on modern PSUs? Contributors Mixxiphoid and Hennes share some insight into the PSU labeling methods. The wattage of your power supply is what it could potentially supply. However, in practice the supply won’t ever make that. I always count 60% of the capacity as the truly maximum capacity. Today however, there are also bronze, silver, gold, platinum power supplies which guarantee a certain amount (minimum of 80%) of efficiency. See this link for a summary of 80 PLUS labels. Example: If your 1200W supply has a 80 PLUS label on it, it will supply probably 1200W but will consume 1500W. I think you 800W supply will be sufficient, but it won’t guarantee you safety. Hennes explains the value of a system-appropriate PSU: The wattage implies the maximum available wattage to the system. However note that the PSU draws AC power from the wall socket, converts it to some other DC voltages, and provides those to your system.

There is some loss during this conversion. How much depends on the quality of your PSU and on how much power you draw from it. Almost any PSU is very inefficient when you draw less then 20% of max rated power from it. Almost any PSU has less than peak efficiency when you draw close to the max rated power from it. Almost any PSU has their optimum efficiency around 40% to 60% of maximum load. Thus if you get a PSU which is ‘just large enough’ or ‘way to big’ it is likely to be less efficient. [But note that your PC does not consume a fixed or constant level of power. At idle, when not much is happening, the DC power consumed will be low. Perform a lot of processing and I/O operations, then power demand goes high.] A nice example of areal world efficiency graph is this: will there be any tangible difference in the outlet wattage draw between a 1200W power supply vs, say, a a 800W power supply? The 800 Watt PSU would run at 62.5% of max rating. That is a good value.

The 1200 Watt PSU would run at only 41% of its maximum rating. That is still within the normally accepted range, but at the low end. If your system is not going to change than the 800 Watt PSu is the better choice. Note that even with a good (bronze+ or silver rated PSU) you are still loosing about 15% during conversion. 15% of 500 Watt means that your computer would use 500 Watt, but the PSU would draw 588 Watt from the wall socket. Clearly, you should aim to have your PSU sized appropriately for your system–putting a high-load PSU into a basic desktop machine doesn’t increase your safety margin and decreases your efficiency costing you more money in the long run. Have a useful link or comment to add to the discussion? Sound off in the comments below. Want to read more answers from other tech-savvy Stack Exchange users? Check out the full discussion thread here. More Articles You Might LikeQuestion: How many 80 watt solar panels to run a house? Answer: Determining how many 80-watt solar panels needed to run a house requires some simple calculations before purchasing the solar panels.

First, determine the amount of electricity that is used each month to power the house. Reviewing a monthly electricity bill from previous months can give a good estimate on the approximate amount of kilowatt-hours that are used. Example: 600 kilowatts of electricity is used each month. There are approximately 1000 watts of electricity in 1 kilowatt of power. To determine the monthly watts used, multiply the number of kilowatts by 1000 watts. In the example above, the approximate usage is 600,000 watts each month. To find out how many 80-watt solar panels needed to run a house, simply divide the 600,000 watts needed by 80 watts for each solar panel to determinate the approximate number of panels needed. Example: 600,000 watts / 80-watt panels = 7500 solar panels This calculation proves that 7500 solar panels that are 80 watts each will provide enough solar power for a house that uses 600 kilowatts of power each month. The solar generated electricity is stored in a battery cell ready for use each day.