Monday, January 30, 2023


RVelectricity: SoftStartHome test on a Honda EU7000i generator

Dear Readers,
I’ve been continuing my experiments with the new SoftStartHome™ controller. I don’t have a full report yet since it’s too cold and windy here in Maryland for a full current/temperature test.

However, I was able to do a preliminary trial using my Honda EU7000i generator to power an entire house along with a 15-year-old, 2-ton York air conditioner on my twins’ house.

Why is this important?

Since power outages are getting to be more common, it’s important that we consider what it would be like to boondock at home. That’s right… much of what you’ve learned while camping off-grid can be useful if the power goes out at your bricks & sticks house.

Now, I don’t think we’re heading back to Little House on the Prairie days, with a total collapse of the electrical grid. Nor do I think that Mad Max will be taking over anytime soon. But I do believe that everyone should plan what to do if your local electrical grid goes down for a week or two. And being able to power the important electrical items in your house is important.

Do I need an air conditioner in a blackout?

Well, if you’re in any of the Southern states, where the temperature gets to triple digits during the day, you’ll soon find that modern houses weren’t built with enough trees and cross ventilation to be comfortable during the heat of the summer.

And this can be especially dangerous for seniors who may have illnesses that can become life threatening during a heat wave. That’s why there’s so much emphasis placed on getting seniors to cool places during a heat wave.

While you may not be able to cool your entire house to 68 degrees while it’s 110 degrees outside using a portable generator, you should be able to create a cool oasis in the mid- to high-70s for a part of your house. Plus, you’ll want to be able to power your refrigerator and freezer during the power outage, and any medical appliances such as a CPAP machine.

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What did I try?

My twin boys have a house with a 2-ton Carrier central air conditioner that’s about 15 years old. It’s time to upgrade it to something with a higher SEER (Seasonal Energy Efficiency Ratio) rating in the spring. So I convinced them I wouldn’t blow up their existing air conditioner during these experiments, which we’ll repeat once the new air conditioner/heat pump is installed.

This was just a proof-of-concept test where we used my Honda EU7000i generator to power the entire house, then cycle the York air conditioner on and off while observing the inrush and static current usage. No, I don’t have full HRDL (High Rate Data Logger) data yet. No, I don’t have data under a range of ambient temperatures. But yes, I did get a baseline inrush power requirement with SoftStartHome for whatever generator you use. Watch this short proof-on-concept video HERE.

It must be a split-phase 120/240-volt generator at least 7,000 watts

While you might be able to start and run a central home air conditioner on a smaller (5kW) 120/240-volt generator, we found that most households will be using at least 1,000 watts of static power, not counting the refrigerator that also has inrush current. So my SWAG (Scientific Wild-A** Guess) is that at least a 7kW generator will be required.

And yes, if you plan on running your central air conditioner and possibly your well pump, the generator must be split-phase 120/240 volts. It will have an L14-30R outlet that looks like this.

You can get a semi-quiet, open-frame, inverter generator for cheap

I really don’t recommend a contractor generator for this application since they use a LOT of gasoline (up to 1 gallon per hour) and their voltage “regulation” can be crude enough to damage home computers, etc.

And while many of you won’t dish out $5,000 for a Honda, or even $2,500 for a Predator quiet inverter generator, there’s another class of semi-quiet, open-frame inverter generators that are even more affordable. Take a look at this Champion 7kW inverter generator with electric start. While it’s not super quiet compared to a Honda or Predator enclosed inverter generator, its fuel consumption seems to be excellent and it should make clean enough AC power for your house appliances. And at less than $1,200, this could be a great fit as a home backup generator.

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Do I know that it works with a Champion inverter generator?

I’m not sure yet, because I’ve just asked Champion for a demo unit to experiment with. Once I have that in hand I’ll be able to do power and SPL (Sound Pressure Level, i.e., noise level) comparisons, plus perform a fuel efficiency test on a static load.

So it will be at least late spring before all of this can happen. My FunkWorks Lab is only 600 square feet, so I don’t have a lot of extra room to set this all up in-situ. But I should have a few other residential air conditioners to experiment on once the weather warms up a bit. Hard to do proper air conditioner testing at freezing temps.

SoftStartHome is the key to making this work

I do know that the SoftStartHome will reduce the inrush current on this 2-ton air conditioner by more than 65%. That 24 amps of inrush current is manageable with a 7kW generator rather than a 10kW or 12kW generator. But we shall see…

FYI: One of my Electrical Engineering colleagues on the West Coast has confirmed that his 3-ton air conditioner won’t start on the Honda EU7000i generator, so I’m shipping him a SoftStartHome unit to try. If it works, he’ll gather inrush and static current measurements, which I’ll add to my database.

Knowledge is power, and we’ll soon know more. So stay tuned for more data in the coming months.

Let’s play safe out there….

Send your questions to me at my 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 For more info on Mike’s qualifications as an electrical expert, click here.

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1 month ago

Mike, has anyone created a “voltage cleaner” that can be plugged into a older generator. I have a 20+ yr old Kabota 6500 that does NOT provide pure sine wave power. I use it occasionally to power my home (only select circuits) during a power outage….and I am too frugal to buy a new gen to replace it. Your comments are appreciated.

2 months ago

While softstart may be useful as a retrofit, when you go to test your new unit next spring, you may find that modern home equipment derails your classic testing theory… I finally installed an 24KBTU “inverter minisplit heat pump” in my log cabin (no ducts, no HVAC possible) this summer and can’t BELIEVE how efficient or smooth the unit is… while 240V, in my max-out testing, it seems to peak at only 8-10A or so while it BLASTS cold or heat. Manufacturer claims it’s up to 5X more efficient moving heat rather than creating it (resistive), but even understanding the science it amazes me to actually experience it feeling like my LP-fired shop-torpedo while only sipping 2KW. Back on why your testing may go sideways, it seems to have a de-facto variable soft start already built in – there IS no meaningful surge upon startup like your traditional 2ton unit there; it just spins up smoothly and almost silently.

Mike Sokol
2 months ago
Reply to  Wolfe

True that the latest inverter/compressor air conditioners don’t have any significant inrush current. But most existing air conditioners with a starting capacitor do have a large LRA inrush current.

2 months ago

We will be snug in the RV.

2 months ago
Reply to  tom

Yep, if the grid goes down that’s where we will be too. Air-conditioning with a lot less smaller generator as I installed the Soft Start in our trailers unit.

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