Converter Consumption

I have used my Kill-A-Watt to measure converter 120v draw when going full out on a low battery, but not when running typical small RV loads.

My instinct (for what that is worth!) is that you might have a situation somewhat like a water heater, where it is easier to keep it hot than it is to get it hot from cold. Or VV with the fridge.

The battery will cycle without the converter, and solar picking it up when it can. If you need to use the converter to bring up a low battery when solar can't, then I think you will use more 120v draw than if you had just left it on Float and run whatever 12v things need it at times.

Cycling the battery also uses up more money, buying batteries sooner, but you can lose your battery from neglect while on converter too.

The real money might be from using an inverter to run all 120v things except air conditioning, if you have enough solar coming in to keep the battery bank up. But that also cycles the batteries and you need more of a battery bank, which all costs money.

Propane is another alternative to 120v for some things. Depends on the math for that if there is anything to be saved there.

Also there is the question of how many days per year is this all about. A car that gets 30 mpg is not an advantage compared with one that gets 10 mpg, if you don't drive it many miles a year.

It's like LED lights in your RV. Only worth it if you have the lights on a lot during a year, and 12v power is in short supply.
People forget that amp-hour means over time, not just the amps.

BFL13 wrote:
I have used my Kill-A-Watt to measure converter 120v draw when going full out on a low battery, but not when running typical small RV loads.

...snip.....

Thanks. My main goal is to reduce my RV park electric charges. They are ripping us off at 17.5 cents per kwh. I will try a combination of propane and solar to cut my bill. Might end up spending fifty to save twenty. No big deal.

When on a metered site, I switch the converter off and let the solar take care of everything 12vdc. Never measured the converter consumption though.

Of course, it depends

On the converter brand

And on the % of the load

The Megawatt 400 idles at 6.7 watts and consumes near 50 watts at full song. The high side is an AC measurement and the low side is a va DC measurement.

Efficiency can be expressed as heat. BTU. Fan output temp is a tough one because of the unknown CFM airflow factor.

This cannot be judged as hard evidence because one random sample was taken.

Say your average DC amps is 5 at 13.6 volts all day. That is 68 watts. Efficiency is 85%, so input watts is 80 watts. Converter has PF of 0.7, so VA required is a steady 114.3 VA. Call it 1 AC amp at 115 volts.

Whatever that is in kw, for an hour is your kwh.

BFL13 wrote:
Say your average DC amps is 5 at 13.6 volts all day. That is 68 watts. Efficiency is 85%, so input watts is 80 watts. Converter has PF of 0.7, so VA required is a steady 114.3 VA. Call it 1 AC amp at 115 volts.

Whatever that is in kw, for an hour is your kwh.

24 hours at 114 watts = 2,736 watts or 2.7 kwh/day

2.7 X $0.175 X 30 = $14.175

Which is worth saving. Even half that would be okay, as I already own the solar equipment.

Our park has that good electricity at $0.175/kwh, not that cheap stuff that most parks provide. (Sarcasm off)

BFL13 wrote:
Say your average DC amps is 5 at 13.6 volts all day. That is 68 watts. Efficiency is 85%, so input watts is 80 watts. Converter has PF of 0.7, so VA required is a steady 114.3 VA. Call it 1 AC amp at 115 volts.

Whatever that is in kw, for an hour is your kwh.

It is unnecessary to apply the power factor in this case; the electric company charges you for kWh, the actual energy used, and not kVAh. In the example, it works out to just shy of 2 kWh each day.

(For large commercial/industrial accounts the power factor is taken into account, along with peak usage and other such things...but not for residential users, at least anywhere that I've heard of.)

My converter has been off for years. Zero consumption due to solar.

Not clear on "actual energy used". When you run the converter from your inverter-generator it draws the 120v supply in VA. The generator runs harder on a 100 amp converter that is not PF corrected than it does on a 100 amp converter that is.

The generator running harder (more revs, more noise, more gasoline being used) is using more "actual energy" seems to me.

Apparent power (what gets added due to a poor power factor) does impose some load on the generation and especially distribution of power, but electric utilities only meter actual power for residential customers; you don't have to pay extra for a poor power factor. Put another way, a standard residential electric meter is measuring and you're being charged only for the actual power, not for the apparent power.

The extra gas being consumed by the generator is not going into powering the converter (the converter isn't using any more electrical energy), but rather into losses in the generator itself due to it having a less ideal load attached to it. No doubt that gas and so forth is of interest to a generator operator, but less interest if you're buying utility power and the power company doesn't charge you for it.