One of the perks of RVing is freedom from shore power. Relying on off-grid power systems is one of the many ways RVers enjoy their camping excursions.
Being fully prepared means you can enjoy the great outdoors even in places where there are no electrical hookups. This is what RVers call boondocking.
One important part of your gear is your furnace. It’s the one piece of gear that’ll keep you warm when temperatures drop.
Today, we’re going to talk about how much an RV furnace amp draws. Knowing that can help you calculate how long the battery can run the furnace.
Let’s get started.
How Many Amps Does an RV Furnace Draw?
The draw of an RV furnace amp relies on the British Thermal Unit (BTU) rating, which dictates the size of the blower fan. For example, a typical 35,000 BTU furnace will draw an average of eight to nine amps. Models that are 40,000 BTU or higher will draw more amperage.
Compare that with a fluorescent light that draws a maximum of two amps per hour, or a water pump or television that draws about four amps of power each.
To make sure the furnace runs without a hitch, it’s a good idea to have a generator or solar-powered system. These provide the power your battery needs to recharge when you’re not connected to shore power.
Calculating the Average RV Furnace Amp Draw
Another way to calculate how long an RV battery can run the furnace is by using some basic calculations.
For lead-acid batteries, start by dividing the battery amp-hours by 2 (AH/2). For lithium-ion batteries, multiply the battery amp-hours by 0.8 (AH*0.8). That should give you the total safe battery amp hours.
Next, take that number and divide it by the number of amps your RV furnace can draw. This will give you the total number of hours the furnace can run using the battery.
Remember to take into consideration the age of your battery or if the weather is cold outside. Just to be on the safe side, it’s better if you take off a couple of hours from the total number of hours.
Here’s an example:
- 120 (total amp hours of the battery)/2 = 60 amp-hours
- 60/8 (average amp draw of an RV furnace) = 7.5 hours
So, under ideal conditions, the RV battery can run the furnace for an average of seven and a half hours.
Bear in mind, however, internal and external factors can reduce the amp-hour capacity. A smart idea would be to half those seven and a half hours. It’s better to have more charge in your batteries than run out of juice when you need it the most.
What Size Furnace is Right for my RV?
To calculate the BTUs required to heat an RV, you have to estimate about 1000 BTUs per linear foot of your trailer. In other words, a 30,000 BTU furnace is adequate for heating a 30-foot RV.
Do RV Furnaces Run on Batteries?
Your RV furnace generates heat from propane tanks. Yet, the blower fan runs on batteries. This fan pushes out the hot air through the vents and into the RV.
What’s the Voltage on My RV Battery?
RV batteries are known as lead-acid batteries. They have several cells connected in a series. Each cell generates about 2 volts.
The number of cells on an RV battery is typically six in a series. So, this type of battery can generate an output voltage of nearly 12 volts. RV batteries help run several of the unit’s electronics, including the blower fan on the furnace.
How Long Does a 12-Volt RV Battery Keep a Heater Running?
As long as you have the right type of battery, your RV furnace will keep running without needing any shore power. That being said, experts recommend you don’t draw over 50% of the capacity on your lead acid battery. This is especially true if you’re camping during the colder months.
Now, we know that the blower fan on the furnace draws up anywhere between 10 to 12 amps per hour. This means that the heater can run non-stop for a little over 12 hours.
However, for safety reasons, it’s recommended that you don’t keep the heater running all that time. Instead, you can turn it on for 15 to 20 minutes each hour just to keep the RV heated. Doing that can get your furnace to run for over 35 hours.
Many appliances are using a 12-volt battery that you might not even be aware of. There are the lights in the RV, the coffee maker, and even the sensors in the fridge.
Take a standard RV fridge of around 6 cubic feet. Even if it’s in gas mode, it’ll draw a little less than 1 amp per hour for the electronic ignition and the sensors.
Now, let’s say you have a fully charged battery that you let sit for several hours. When it’s time to turn on the furnace, the fridge alone will have used up almost five amps from the battery.
To avoid having a dead battery, you must have a way to charge them. This could be either a generator or a solar-powered system.
Also, make sure you’re always prepared when it comes to powering your gadgets. If you’re going camping for more than two days, make sure you have a couple of 12-volt batteries. Keep that extra battery not hooked up until you need it.
Remember to never run the batteries past their 50% capacity. It can cause lasting damage to your batteries.
A Final Note
Nothing can be better than escaping for a few days with your RV. All that fresh air, being one with nature, and all that calm and quiet.
Knowing your total RV furnace amp draw goes a long way when you’re boondocking. It can help you calculate how long the battery can keep the furnace running. This way, you can enjoy camping with all the basic comforts of home.