AC or DC

In the context of home power systems, the term "AC" generally refers to 120 or 240 volt alternating current of the type normally found in homes and industry. This form of electricity has the advantage of being efficient to distribute over long distances (via powerlines) and is easily converted to whatever voltage is required for any particular device through the use of transformers. This conversion process is probably familiar to you in the form of plug in adapters (wall cubes) used to power electronic equipment such as answering machines, cordless phones, etc. Many other electronic devices have transformers enclosed within their cases to perform this function.

DC, in the context of home power systems, generally refers to low voltage direct current as stored in the batteries of the system. Thus, in a DC system, electricity is fed directly from the batteries to the loads in the system. Most DC only systems are 12 volts because of the wide availability of 12volt equipment.

Advantages associated with AC:

• Most appliances, lights, and electronic equipment are configured to operate on AC or "house current"
• AC is efficient for long wire runs
• The wiring and equipment required for safe distribution of AC power within a home is widely available and much less expensive than its low voltage DC counterpart.
• A home wired for AC power is ready for utility or generator power if / when it is available.

Disadvantages:

• Much of the equipment designed for AC operation is inefficient if not downright wasteful - Shop Carefully!
• The incorporation of AC power into a home power system requires an inverter to transform electricity from the batteries into AC. Inverters cost between $500 - $3000 for typical home installations. ( Often, however, this cost is partially or completely offset by the elimination of expensive DC wiring, especially in larger systems.)
• The conversion process from the batteries to wall outlet, light, etc. typically wastes 5% to 15% of the converted electricity, even in a well designed system.

Advantages associated with DC:

• Requires no inverter, therefore reducing system cost and complexity (in smaller systems)
• Efficient, as long as no long wire runs are required (more than 100’ or so)
• On systems using less than 48 volts, there is very little risk of accidental electrocution.
• A good share of the equipment designed to run on DC is highly efficient.

Disadvantages:

• Higher cost associated with wiring large systems with DC because of larger wire, switches, fusing, etc. required for low voltage, high current applications.
• DC appliances and equipment can be difficult to obtain.
• Wiring a large DC only system to code can be a NIGHTMARE! ( although smaller DC systems can be made very safely with little expense )
• Increased fire hazard if wire size requirements and maximum circuit ratings are not strictly adhered to.

IN A NUTSHELL:

• DC only systems are usually desirable when creating small, high efficiency systems such as a small cabin with a couple of lights and a radio, typical RV / camper installations where AC power is not a requirement, water pumping systems, remote telemetry sites, etc.
• AC systems are usually desirable for medium to large homes, any system that will be required to operate AC equipment, or anywhere that requires long wire runs.

Call or write us if you have any questions.

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