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RVelectricity™: How much energy do you need to power RV appliances? Part 1

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Dear Readers,
Since the English language is simply too small to encompass my thoughts and discussions on the amount of battery and solar energy needed for common (and not so common) RV appliances, I’m introducing two new words into your vocabulary: CEUs and PREUs (pronounced like cues and prunes, but without the “n”).

In the beginning, there were SPEUs

Of course, this is simply an expansion of my concept of SPEUs (pronounced like spew, as in spew forth), which I created to discuss the amount of energy required to make a sock puppet with a sewing machine. Hence, Sock Puppet Energy Units were born. Please go back and reread my SPEU article for a refresher HERE

In today’s article, I’m going to discuss the amount of energy needed to make a cup of cappuccino or coffee (hence, CEUs for Coffee Energy Units) or run a portable 12-volt Danfoss refrigerator (hence, PREUs for Portable Refrigerator Energy Units).

Study time…

This sort of mind experiment will help you understand just how much battery energy is needed for any electrical appliance in an RV. There’s a little bit of math involved (actually just simple arithmetic), but most of these calculations can be performed by counting on your fingers and toes. That means you can put away that slide rule for now…

So please keep your arms and legs inside the ride at all times until it comes to a complete stop. This is your first electrical learning experience of the new year.

The Portable Power Station

No, I will not call these things solar generators, since these are basically lithium batteries and a pure sine wave inverter in a box with plug-in solar panels, but Portable Power Station is a reasonable nom de plume…

That’s why a few months ago I asked for a Jackery 1500 Power Station with 1,500 watt-hrs of battery storage, an 1,800-watt pure-sine-wave inverter, and 400 watts of solar panels (200 watts shown here). Now, this portable battery/inverter will certainly not replace a hard-working generator to power your entire RV, nor do I think it’s time to rip out your existing RV’s converter/inverter/battery system. But as a supplement for boondocking without a generator it’s a solid concept. So that’s what I’m using for these next two energy usage experiments.


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How much energy does a Jackery 1500 store?

Well, the Jackery 1500 is listed to be able to provide 1,500 watt-hrs of battery storage, and my casual observations confirm this. So you can run a 1,500-watt space heater for 1 hour (because 1,500 watts times 1 hour of time equals 1,500 watt-hrs).

Or it could run a 100-watt light bulb for 15 hours (because 100 watts times 15 hours equals 1,500 watt-hrs). Now, there is inverter overhead (the fan) and inefficiency losses when it makes 120-volts AC. So, some of my testing includes powering a Vitrifrigo Portable Refrigerator both from 12-volts DC directly as well as the 120-volt AC inverter. Spoiler Alert – No surprises, since the portable refrigerator could run for nearly twice the number of hours using 12-volts DC compared to 120-volts AC.

How many CEUs does it take to make a cappuccino?

Okay, now it’s time to answer the question I get asked every week on my various forums and blog. Just how much battery power will it take to make an espresso, latte, cappuccino, or mug o’ joe in my RV? I’m thinking in Coffee Energy Units, or CEUs for short.

While there are old-school ways to heat water on a propane-powered cooktop, many of you still want your Nespresso machine. Apparently some of you made deals with your better halves that they could bring along their favorite caffeine machine, or they wouldn’t go boondocking in the woods with you. So now it’s a deal breaker if you can’t deliver the java…

The setup…

I plugged my Nespresso machine into a Jackery Explorer 1500 which has an onboard 1,500 watt-hr lithium battery and 1,800-watt pure sine wave (PSW) inverter. The Jackery has a very nice Power/SoC (State of Charge) meter, which makes it pretty easy to get both power and energy usage data.

As you can see in this short video HERE (or click on the picture above), there’s 1059 watts of power draw from my Nespresso machine during the warmup cycle, followed by around 850 to 900 watts during the milk foaming cycle, followed by 550 watts down to 208 watts during the espresso pumping cycle.

The data…

We can see from this short video that the peak wattage used is just over 1,000 watts, so a 2,000-watt inverter should easily be able to power this Nespresso machine, as long as you don’t have the microwave oven running at the same time.

And the SoC started at 87% and ended up at 85% at the end of the cycle. Since this is a 1,500 watt-hr storage battery, all we have to do is multiply 2% times 1,500 watt-hrs and calculate 30 watt-hrs of energy needed. So I’m going to estimate that each CEU (Coffee Energy Unit) is around 30 watt-hrs of energy for a Nespresso machine making cappuccino.

Flipping the calculation, you’ll see that if you have a single 100 amp-hr AGM or FLA (Flooded Lead Acid) battery, the 600 watt-hrs of available battery energy divided by 30 watt-hrs (1 CEU) needed per cappuccino cycle equals 5% of your available battery power, which is 20 espresso-making cycles on a battery charge.


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The calculations…

If you have a 100 amp-hr lithium battery in your RV, that’s around 1,200 watt-hrs of available battery power (since you can discharge them down to 0% SoC). So you could make 40 cups of cappuccino on a single battery charge.

And the Jackery 1500 should be able to make 50 cups of cappuccino on a single charge, which I’m not going to actually test since I’m pretty sure I can’t drink that much caffeine in a day. But the math indicates that’s how it should work. And if you consider that 400 watts of solar panels can recharge around 1,200 to 1,500 watt-hrs of battery power in a day, it suggests that you could make 50 cups of cappuccino per day FOREVER, as long as the sun is shining and you don’t run out of pods.

Part 2: More info to come next week…

Note that this type of test can be modified to include things like air fryers, induction cooktops, and toaster ovens, all of which use a LOT of power to operate.

But next week I’m going to show you how long you can power a Vitrifrigo portable 12-volt DC refrigerator from a Jackery Explorer 1500 Power Station or your RV’s house battery.

However, there are different possible operational hours using 12-volts DC directly, and stepping it up to 120-volts AC with an inverter. That’s because the available PREUs (Portable Refrigerator Energy Units) per battery charge change by nearly 50% with the 120-volt AC inverter compared to directly powering it with 12-volts DC. Inverters making 120-volts AC really are energy hogs compared to powering an appliance with 12-volts DC directly, whenever possible. So this is vitally important information if you’re planning to boondock without a generator. See, knowledge really is power!

See you next week for Part 2… 

Let’s play safe out there….

Send your questions to me at my new RVelectricity forum here.

Mike Sokol is an electrical and professional sound expert with 50+ years in the industry. His excellent book RV Electrical Safety is available at Amazon.com. For more info on Mike’s qualifications as an electrical expert, click here.

For information on how to support RVelectricity and No~Shock~Zone articles, seminars and videos, please click the I Like Mike Campaign.

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LER
11 months ago

Very helpful Mike. Putting it into terms that describe usage takes the mystery out of the equation.

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