autoformers for dummies (me)

pianotuna wrote:
Hi all,

I've heard folks saying autoformers "steal" power from the campground and hence from other campers. Here is my understanding of what happens.

The total wattage remains the same less about 4% overhead for running the autoformer.

The volts come by swapping amps for volts.

i.e.

Input to autoformer (not including 4% overhead)

100 volts X 12 amps = 1200 watts

Output from the autoformer

120 volts x 10 amps = 1200 watts

I won't run my roof air on low voltage. I chose 1200 watts as an example because that is about where my roof air starts out at. It is also the maximum number of amps for a continuous demand on a 15 amp circuit.

More usually, in real life, I'll be boosting from just below 110 volts to 120 volts, so the "true" numbers would be

Output to RV 118 volts X 10.17 amps =~ 1200 watts

Input required to the autoformer 108 volts X 11.11 amps X 1.04 (overhead on autoformer) = 11.55 amps or ~1248 watts.

See the area I outlined in bold.

Folks that say autoformers are "stealing" or "cheating" the campgrounds power ARE technically correct.

Since a autoformer is not lossless there is 48W MORE power being drawn from the input than what you get from the output..

Put it this way, IF the campground had a power meter on your site YOU would be paying for 1248W but only getting 1200W worth of energy to use..

Now multiply that 48W x the amount of camping spots and it will be pretty apparent that the campground WILL have even a larger loss in costs..

For instance say the campground has 500 spots and EVERYONE decided to use a autoformer, the campground will pay for an additional 24Kw of power per hr use.. for 24 hrs that would be 576 Kwhrs per day the campground would have to pay for!!

My home electric cost me about $.07 per Kwhr (some places pay $.11 per Kwhr) at a residential rate.. That would be a $40.32 per day loss for the campground..

HOWEVER, with electric power you do need to understand that BUSINESSES do not pay residential rates.. They pay at COMMERCIAL RATES which ARE MUCH HIGHER.. Typically commercial power will cost about DOUBLE RESIDENTIAL RATES!

That would mean that my example would now be about $80 PER DAY the campground would pay..

It is for that reason some campgrounds have rules about autoformers..

Put yourself into the shoes of a business owner.. You would not be happy with having your business costs go up.. You would have to take action somewhere to trim costs OR RAISE CAMPING RATES..

Use only what you need.. Don't waste power, water, ect by abusing privileges..