While some RVers are minimalists who go with nature and live on minimal power consumption, others can’t live without the air conditioner, fridge, large-screen TV, microwave, and hot water. It’s important to know whether your RV battery is ready for that load. Also, how long can it keep powering up these devices before being depleted? To plan an enjoyable trip, it’s wise to ask yourself, how many amp-hours do I need for my RV?
Most RVrs agree that 220 amp hours are enough for running a few appliances and for watching tv. However, this is not a one-size-fits-all answer. How many amp-hours you need depends on how many appliances that you’ll be using, whether or not you want to bring along a generator for recharging, and so on.
Keep reading as we’ve detailed how you can find out exactly the number of amp-hours that you will need for your rving adventures!
By the way, as an Amazon Associate, I earn when buying qualified products through links on my site.
Importance of Knowing How Many Amp Hours for RVs?
Knowing stats like the max speed a vehicle can run, or what vanity tires can fit on its chassis is amusing. It always makes for good conversation. But there are other figures that are necessary to know. One of these, is the power requirements of your RV.
Here are some of the ways it comes in handy.
- Selecting a suitable RV generator.
- Selecting a battery with sufficient capacity.
- Installing an inverter that matches the AC/DC settings.
- If you plan to go to an RV park, you’d know your usage limits.
- If you share a friend’s electricity outlet, you can pay for your usage.
- Your power consumption bill wouldn’t be a surprise.
- Your trip will not be interrupted by a power outage.
- You can increase or decrease the number of appliances to match the battery.
A Few Tech Terms First
To understand the whole process of power requirements, it’s best to demystify a few terms:
This is the potential power a generator or battery is capable of giving. It’s the force that drives a current through a wire and eventually makes a device come to life.
Whether that is by making a motor move, giving sufficient energy for a heater to start emitting heat or exciting a wire inside a light bulb so it lights up a room. The voltage expresses how big of a motive the electrons have to run along a wire.
This is the number of electrons that can flow in a conductor/wire in any given second. If you connect a simple circuit to a 1.5-volt battery and attach a tiny LED lamp to it, then as soon as you close the switch, the lamp lights up.
That’s because current flows from the battery, through the wires, into the LED lamp. Current is like water that runs through a conduit, if the tube is large, and there’s little resistance to the water, then the water will be plentiful. The water pressure at the faucet is like the voltage in a circuit.
Current can be direct (DC) or alternating (AC). This depends mainly on how electricity is generated. A battery generates electricity through a chemical reaction that preserves the polarity of each terminal at all times.
AC current is generated through a dynamo that converts motion into electricity. The dynamo changes its polarity 50 or 60 times per second, and this is what creates the frequency component of an AC current.
Devices that use up higher amps are often run by AC sources, and involve moving powerful motors, or creating a large amount of heat. Air Conditioners and stoves are good examples.
Voltage alone, or current alone, does not describe the state of an electric circuit properly. That’s why scientists came up with power. This entity is the product of both the current and the voltage.
Here’s how it’s stated:
Power (watts) = voltage (volts) x current (amps)
This is a good predictor of the electric needs of any appliance, as well as the capabilities of an electric source. Generators are often rated by their wattage. For example, RV generators often come at 3500-watt ratings.
Most devices run for a certain duration of time. You can leave the lights on for three hours, the TV for half an hour, the electric kettle for a minute, the hairdryer for 10 minutes, and the air conditioner for the whole day.
Each one of these devices has a power rating in watts, and it runs for a specific amount of time in hours. Thus, it’s reasonable to describe the total power consumption as a product of the two entities.
Power usage (watt-hours) = power rating (watts) x operating time (hours)
This is also the number that appears on your electricity bill, and it’s often expressed as KW hour. The ‘K’ means that the watts logged in are in the order of thousands. This is the regular power consumption of a household.
This also describes power consumption, but in the specific case of using a battery. The rating describing the battery capacity is often given as amp-hour (AH), which is the amount of power it can supply in a certain amount of time before depleting.
This rating is often twice the amount that you can use for your appliances. So when you read the rating on the battery label, divide that amp-hour value by two. You can only use 50% of the battery’s limit.
You can easily convert watt hour to amp hour by using this simple calculation:
Power (watts) = voltage (volts) x current (amps)
Current (amps) = power (watts) / voltage (volts)
Power consumption (watt hour) = power (watts) x time (hours)
Current consumption (amp hour) = power consumption (watt hour) / voltage (volts)
The last line is really what you should focus on. This is how you can calculate the amp hours of your RV. In the next section, this will become clearer, as we get into more details.
How to Calculate the Watt Hours and Amp Hours of the RV?
This procedure is quite simple, despite the number crunching!
Step 1: Read the Labels
Make a list of all the appliances that you have, and log in the rated voltage and current. There would be several other numbers on that label, and a bunch of quality markings, but disregard all that.
Step 2: Get the Power consumption for Each Appliance
Calculate the power in watts for each device, which is the product of the current and voltage you just read from the labels.
If the label doesn’t clarify the voltage or current, you can read out the power consumption of the appliance from a wattmeter (see on Amazon).
Some appliances use up a spike of power on startup, so you might as well account for that by writing a higher number, or reading it out from the wattmeter.
Multiply each power rating by the maximum estimated time of operation. This should give you the power consumption for each device.
There are also devices you can buy and plug your appliance right into it and find out the specific power consumption of each device. This is one of my favorites. (see on Amazon)
Step 3: Add Up All the Estimated Power Usage
Calculate the power consumed by the devices powered by the shore power, which is the 120-volt appliances. Then repeat for the ones powered by the battery, the 12 volts DC devices.
Add up all these values, and you’d get the total power required in watt-hours.
Step 4: Convert to Amp Hours
Use the simple mathematical calculation of power conversion to get the amp hour value for power consumption
Power (amp hours) = power required (watt hours) / voltage (volts)
Battery selection and appliance usage, depend completely on the correct estimate of the power requirements. At this point, you can plan a fun trip with all confidence!
This was the easiest way to know how many amp-hours you will need for your RV battery. You can also install a monitor on your battery, to be sure your calculations are in accordance with your actual usage. Then, make adjustments as needed.
This way, you can make sure that you’d have an abundance of uninterrupted power throughout your trip.