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Get Powered Up! Certified Energy Manager Jeff Yago answers your alternative energy questions

Wondering about a great new energy-saving device
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Sorry. Jeff no longer answers questions online.
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Archive for the ‘Air conditioning’ Category


Camper shell A/C

Sunday, June 21st, 2009


I saw a question about air conditioning a camper shell for dogs. The answer was to let the dogs ride in the front.

I am looking for a way to A/C my camper shell as well. I have a heavy duty alternator in my pick up.



Several companies make a 12 Volt DC powered air conditioning unit for truck cabs that can be powered from an alternator charged battery. They are not cheap and they usually require adding a heaver dual battery power system, but you can buy these.

I think you will find the cost will be so high that its not worth the trouble, but give it a try.

Good Luck,

Jeff Yago


Solar panels for heating / air conditioning

Thursday, January 8th, 2009

Good morning, Jeff,

Your article was very interesting about the solar panels on the trailer. (the big block of panels, I think they were four together)

Can you tell me if having a small system like that, or even duplicating the system, putting it on my big roof, attached to a big heater, (or an air conditioning element for the summer) lets say for a big lounge, and on all the time, can this be done?

People, here say that it cannot be done. That it has to be attached to the electric company and all that rubbish. I cannot see why if it works independently for a trailer, why it cannot work for a room (wiring apart, of course)

Please, with your knowledge, let me know more. I would like to do these small moves, one at a time, to save on my gas bills, too, too high.

Thanks for now, and I thank you in advance for your precious knowledge and will use it to the best use.


Buon Giorno Signorina Maria!

You did not say where you lived in Italy, but I have worked in many different cities in Italy and Sicily and they are all molto bella.

A system the size of the solar trailer would not power an air conditioner or heater, and if you enlarged the system you would find it very, very expensive. I know most homes there were using compact fluorescent lamps years before we were in the US due to the higher cost for power there. If you are in an area that has many power outages, you might consider a small solar system like the solar trailer to power your refrigerator, television, and lighting during a power outage.

If you do decide to do this, remember to select an inverter that matches your local electric voltage and frequency cycles as some areas use 240 volts at 50 cycle, while inverters designed for the US market are 120 volts at 60 cycles.

Italy, Spain, and Germany are far ahead of all countries, including the US, on solar incentives and I suggest that you check with your energy department to see if you can take advantage of these solar buybacks. Perhaps a grid tie system may be your best bet since it costs less, does not require batteries, and most likely would receive some type of rebate to offset the cost.


Professor Jeff Yago


Air conditioning for a pickup camper

Thursday, November 27th, 2008

Hi Jeff.

I would like to put Air conditioning in my pickup truck camper shell to keep my dogs cool in the summer. It would only be in use when I was traveling down the road, not while the truck was turned off. Here was what I was thinking – could you offer an opinion on whether it would work or how to to do it, if it is even possible.

[I want to] put an RV air conditioning unit on the top of my camper shell and run that off an inverter connected to my pickups battery.

I do have a 2500/5000 watt inverter but I wonder if the air conditioning unit would suck so much energy that the alternator could not keep the truck battery charged up going down the road.. My truck has two batteries up front


Hello, MIke.

The problem is not battery size, it’s your alternator capacity. There is no way an RV air conditioner can run off one or two truck batteries for more than a few minutes without draining them. For example, the smallest, newest, and most efficient truck camper AC unit draws 8 amps at 120 VAC. Assuming a 90% system efficiency, this would be a 1,100 watt “run” load on your inverter, and require an inverter that can handle at least 2 kW “start” load since any compressor load is a dead short on the power source for the first few seconds it is trying to rotate.

You said you had a 2,500 watt inverter which should be able to handle a small RV air conditioner, but that is not your main problem. Your inverter will have a constant draw of 88 amps at 12 volts DC while an 8 amp load air conditioner is running, and could draw up to 150 amps for a few seconds every time the compressor kicks in. This means your truck alternator and all related cables need to be large enough to handle these larger current flows and still have enough excess power to operate your lights and other electrical loads in the truck. Each time you stop at a light, there will not be enough amps coming from your alternator even if it is a larger 150 to 170 amp heavy duty model.

This is why the air conditioning unit in an RV is always wired into the exterior shore power or generator panel, and not powered from the batteries. Any 120 VAC electrical load on an inverter will draw 11 times the AC amps from a 12 volt DC battery.

I suggest letting the dogs ride in the back seat!

Jeff Yago


Solar panel on car

Thursday, October 30th, 2008

Hi Jeff,

I find your articles on 12 volt interesting. I’ve often thought about cars having eg. a roof that was a solar panel which would be connected to a rechargable ni-cad battery and then to an air conditioner / heater which would keep the cabin of the car cool or warm.

Any thoughts?


Frank Savoy


A solar module is not magic, it does not make energy, it just collects the sunlight energy available and converts this from solar photons to electricity electrons, and even the best are only about 10 to 15% efficient. Using your example, lets put a solar module about the size of a car skylight. What ever solar energy is striking the solar module, you only get 10 to 15% of that as electricity, which we wire up to your example electric car heater. Now if we remove that solar module, and let the same amount of sunlight pass on through into the cars interior, almost all of that energy will be converted to thermal heat, not 10%.

In other words, unless you enlarge your car’s roof to mount the 400 square foot solar array you will need to power a small AC unit or electric heater, the only thing a normal size solar module will do on a car roof is keep the battery charged if you like to park for hours and operate the radio or laptop computer!

Hope that helps,

Jeff Yago



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