With improvements in solar charging and the availability of portable generators, RVers are no longer so limited by a campground’s hookups. But when you aren’t plugged into a shore power pedestal (and even sometimes when you are), you may not have sufficient power to start your air conditioner. That’s where an RV air conditioner soft start can improve your experience.
Some manufacturers now install soft starters in their air conditioning units at the factory. If your camper doesn’t have one, adding this RV AC upgrade can help you start your AC when the generator or shore power is insufficient. Let’s explore how an AC soft start works, why you might need one, and how to install one in your RV.
What Is A Soft Start for an RV Air Conditioner?
A soft start is a device installed in line with your air conditioner’s compressor to reduce start-up power requirements. They are typically mounted inside the roof-mounted unit under the A/C shroud, but some also plug into the shore power pedestal.
The better soft starts also act as a “line conditioner”. This means that, aside from the start-up benefits, they keep the AC voltage and amperage at consistent levels, even when other A/C electrical loads are applied in your RV or in other RVs nearby on the same circuit.
How Does an RV AC Soft Start Work?
When the compressor starts up and draws a lot of amperage from the system all at once, the soft start capacitors release their stored energy to supplement the energy supplied by the electrical system. The result is far less load on the RV’s AC electrical network. Since the compressor spins up more easily, it experiences less wear over time.
The reduced start-up load means that other A/C electrical appliances can be operated while the air conditioner is running, without concern for dimming or brownouts. The presence of a soft start also enables the use of inverters and smaller, quieter, more fuel-efficient generators. It even helps when you have to operate your 50-amp RV on a 30-amp pedestal.
Every RV air conditioner has two important power ratings: starting and running. The starting requirements are how much power the unit needs to power on, and the running requirements are how much power it needs to stay running.
The starting requirements are much higher than the running requirements. A lower starting power requirement makes it easier to power up, putting less strain on your electrical system and reducing wear and tear on the compressor. These requirements are listed as “watts” or “amps.” Using an online calculator, you can easily convert watts to amps or amps to watts if needed.
Why You Need an RV AC Soft Start
There are many reasons to use a soft start, even if you’ve already explored other options for improving AC efficiency. But there are also a few reasons not to. Let’s take a closer look at these below.
Off-Grid Use
One reason to add a soft start to your AC is that you like camping off-grid using a generator. Generators allow you to explore more and avoid crowded campgrounds.
The problem with running your air conditioner on generator power is the large amount of power it requires at start-up. At a minimum, you’d need a 3,500-watt generator to power one 13,500-BTU RV air conditioner. In cases where you have a 15,000-BTU unit or multiple air conditioners, the generator sizing can double. The more power your generator offers, the louder, more expensive, and physically larger it will be.
Adding an aircon soft starter can reduce your air conditioner’s starting power requirements by up to 70%, allowing you to use a much more cost-effective and physically smaller generator.
Technician Tip: As the industry changes rapidly, watch for DC air conditioners and digital A/Cs that run on inverter power (from your batteries). A soft start is often required for these units and is typically installed at the supply side near the battery bank.
Start-Up Noise
If you’re a light sleeper, you’ve probably been awoken by the air conditioner booting up in the middle of the night. This is especially true if you have an AC unit directly above your bed. A soft start reduces the noise an air conditioner makes during start-up, allowing you to sleep more peacefully.
Technician Tip: A soft start won’t reduce a unit’s noise level while running.
Wear and Tear
By limiting voltage spikes to the compressor during start-up, an RV AC soft start reduces wear and tear on your cooling system over time. The less wear and tear you have, the more reliable it will be and the longer it will last. In other words, a soft start can save you money by extending the life of your system and reducing the frequency of replacements.
Speaking of replacements, check out our guide to choosing the best RV AC replacement if you’ve decided it’s time.
Shore Power
A soft start isn’t exclusively for generator use; you’ll also benefit from using one at the campground or when plugging into power at home. For example, if you have a camper with multiple air conditioners and the park only offers a 30-amp service, you may not be able to run both units due to the high start-up demands.
However, with a soft start, you’ll reduce the total starting requirements, increasing your chances of powering both units simultaneously. When camping at a metered location where you pay for electricity separately from your site rental, an AC soft start eliminates surges to the grid power system.
This can matter most to owners who keep their RVs plugged in at home, as most residential electric bills are graduated for peak hours and surge usage. Having a soft start, especially one that connects to the shore pedestal, eliminates or greatly reduces the demand and surge signatures monitored by power companies. The result can be significant reductions in the electric bill.
Technician Tip: A soft start is installed on a single air conditioner; if you have multiple, you must purchase a separate soft start for each, or one that attaches to the shore pedestal or between the shore power cord and the distribution box, which assists all 120VAC systems.
Is a Soft Start for RV AC Worth It?
Although admission is expensive — most range from $200 to $400 — a soft start can be worth it for off-grid campers using a generator or those with multiple air conditioning units. If you only stay at campgrounds with dedicated 50-amp service, you might not find as much value in a soft start air conditioner. For everyone else, they are absolutely worth the money.
Several brands make RV-specific soft starters, so it’s worth comparing options before you buy. SoftStartRV®, Dometic®, and Micro-Air® are some of the most established, and compatibility and features vary by AC brand and model.
What Tools Do You Need to Install an AC Soft Starter?
To hardwire your AC soft start, you’ll need a few tools.
- Screwdriver (Hardware varies by manufacturer)
- Wire Strippers
- Wire Crimper
- Electric Tape
- Test Light or Multimeter
Once you have the correct tools, you can begin installation.
How To Install a Soft Start for an RV Air Conditioner
Although an AC soft start kit can plug into the shore power pedestal, most must be wired into the air conditioner. You can use these general tips and practices for most installations.
You can use these general tips and practices for most installations.
- Turn off the breaker and unplug the shore power.
- Ascend to the RV roof and remove the air conditioner shroud.
- Identify and locate the compressor and start capacitor (cover panels may need to be removed to access these components).
- Locate the air conditioner’s model number and obtain the wiring diagram from the soft start manufacturer.
- Attach wires from the soft start to the compressor and start capacitor, and use electrical tape to insulate all connections.
- Mount the soft start inside the overhead unit with the connector facing down, clear of other components.
- Reinstall cover panels and overhead shroud.
- Apply power to the breaker and check for proper operation.
Technician Tip: Always refer to the installation instructions for specific steps and wiring instructions. If you don’t feel comfortable completing the installation yourself, contact one of our local service centers. The referenced “start capacitor” is your air conditioner’s original capacitor. The soft start kit wires into it, rather than replacing it.
Technician Safety Tips
Use this safety advice from our expert technical service team to stay safe during this installation.
- Discharge the existing start/run capacitors before installing to reduce the chances of electric shock.
- Never work on high voltage alone.
- Utilize fall protection anytime you are working on elevated surfaces.
- Consider insulated tools or dielectric gloves to reduce the risk of electrical shock.
- Check for insect nests before removing the A/C shroud.
RV AC Soft Start FAQs
The main drawbacks of a soft starter are cost (most units run $200-$400) and, if hardwired, the expense of professional installation. A soft start also won’t reduce your AC’s overall power demands. It only lowers the initial startup surge.
A soft start solves one specific problem: insufficient power to start the compressor. If your AC still won’t start reliably after a correct installation, the soft start likely isn’t the solution to your issue.
A soft starter can mask a failing or weakening AC capacitor or compressor. If the compressor begins to sound like it did without the soft start, it could indicate an issue with the soft start, the AC capacitors, or the compressor. A quick diagnosis can catch the issue before the system fails you at the campground.
A soft start can improve AC performance, but it can’t fix issues. Our RV Air Conditioner Troubleshooting Guide covers power issues, water leaks, unusual noises, and more — a good next stop if you’re still troubleshooting.
Let us know in the comments below if you have a soft start kit and how you like it.
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