Power loss and efficiency when converting house AC to 12V DC with transformer and rectifier

If you use step down transformer at the panel to produce D/C power in a house which of course is A/C power; is there any loss or waste of power?

Does this reduce the amount of electricity used?

A step down transformer by itself will not produce DC, it will produce low voltage AC. Most if not all you appliances will not run, many may be damaged but you may save power as you will not have anything that works or draws power anymore.

Power is power and that is what you pay for. Power is voltage times current, if you reduce the voltage on your load but your load needs a certain amount of power to function you then must supply it with more current. More current usually means more losses because wires have resistance and will heat more with more current (I^2R losses) so you have more loss. That is why power companies use very high voltage lines, to reduce the current losses.

John,

Let me re-phase my poorly worded question.

All appliances, lights and devices can be manufactured to run on DC power, some already are, with the exception of high use items such as HVAC, range, refrigerator and dryer, which can run on gas.

I know the flaw in DC power in that you would have to have electricity plants closer to the house than with AC.

I am familiar with the plumbing comparison of pipe size and pressure.

1. If you deliver electricity via AC power to the home or office at the panel, how would you transform it to DC power?

AC to DC converter?

Would you store DC power in a battery?

What is the loss of power in the conversion?


2. Houses currently use 14 gauge and 12 gauge wire for outlets, switches and light fixtures. What problems are associated with running DC power through existing large wires?

3. In simple terms, would the amount of actual electricity used be less? Thus using less energy and lowering the cost.

For example, if you have an alarm clock using 120 volt AC and the same exact alarm clock using 12 volt DC power supplied to the house as described in number one and two. Would there be an energy savings with the DC clock?

Same question as above except, the household large gauge wiring is replaced with small gauge DC wiring?


4. DC power would not need GFCI protection, right?


5.Would DC power create enough of an arc to start a fire and thus need AFCI protection?

6. What is your area of expertise?

Lenny,

Let me answer your questions:

_1. If you deliver electricity via AC power to the home or office at the panel, how would you transform it to DC power?
AC to DC converter? Would you store DC power in a battery? What is the loss of power in the conversion?_
Depending on the power levels, a bridge rectifier all the way up to a IGBT bridge. The idea is that you reverse the polarity of the AC at every zero crossing so it is always positive feeding the circuit. It is then regulated to the proper voltage. More sophisticated circuits can combine these steps. A transformer is frequently used to drop the AC to a lower voltage before regulation so that the regulator is more efficient (in the case of a linear regulator but is not so important for a switcher.

_2. Houses currently use 14 gauge and 12 gauge wire for outlets, switches and light fixtures. What problems are associated with running DC power through existing large wires?_
If you plan to deliver the same amount of power you will need more current and therefore larger wire but other than that, there should be no issues.

_3. In simple terms, would the amount of actual electricity used be less? Thus using less energy and lowering the cost._
If your loads were converting 120VAC to low voltage DC and you can drive them directly than you may save a little.

_For example, if you have an alarm clock using 120 volt AC and the same exact alarm clock using 12 volt DC power supplied to the house as described in number one and two. Would there be an energy savings with the DC clock?_'
If you can save a conversion step than it will likely be a little more efficient, it all depends on how efficient the converter int he alarm clock was versus the bulk conversion going into the house.

_Same question as above except, the household large gauge wiring is replaced with small gauge DC wiring?_
The smaller the wire the larger the losses.

_4. DC power would not need GFCI protection, right?_
Depends on the voltage, less than 12VDC is generally thought of as a save level. But I would not want to get int he bath tub with it.
_
5.Would DC power create enough of an arc to start a fire and thus need AFCI protection?_
Yes, particularly in the presence of a volatile gas or fuel. Circuits need to be intrinsically safe not to create a spark, that is a whole different subject. Whether or not you need arc fault protection really depends on where you are putting the circuit. Just like the GFI question, there are places I would use it even at 12VDC although others may consider it overkill.

_6. What is your area of expertise?_
Over 35 years in industrial electronics, there is hardly an area that I have not worked in.