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Disclaimer
The information in this article is not all inclusive of what you will need to know in order to safely modify your RV, travel trailer, 5th wheel or any other item with a 12 Volt electrical system. Similarly, we do not claim nor guarantee that all the information presented in this article is correct, and the information is only provided to share the research and information we learned from personal experience while modifying our 5th wheel. We are not certified electricians or electrical engineers. We are only RV enthusiasts and hobbyists. 12 Volt batteries are dangerous if not handled properly. Failure to follow the correct procedures with your batteries can lead to shock, shorts, mishaps, overload, acid spills, sparks, battery explosions, fire and many other serious incidents. Working with and modifying the wiring and electrical system on your RV is potentially hazardous and can lead to shock, shorts, mishaps and the possibility of fire, injury or other serious consequences if not done correctly. Similarly, modifying or adding batteries or modifying or working on your RV electrical system can lead to damage of your RV’s electrical system and electrical components if not done correctly. If you plan to work on your RV batteries and/or electrical system, you should consult an experienced electrician and/or your local RV dealership’s qualified technicians to make sure that you are following the local electrical codes and proceeding safely with your modifications and not voiding your RV warranty. Similarly, it is important to follow all manufacturers’ instructions for the batteries or electrical items you purchase and intend to use. BigBoyToysOnline, LLC will not accept responsibility for any mistakes, mishaps, injuries or deaths that occur as a result of anyone trying to make modifications to their RV, travel trailer, 5th wheel or any other item based on the information in these articles. This is SERIOUSLY DANGEROUS stuff. Please proceed carefully and safely!
Choosing the Right Inverter
In order to choose the right inverter for your needs, there are several things to take into consideration before making your purchase. Some of the questions you need to ask yourself are:
- Do I need a pure sine wave inverter or can I get by with a modified sine wave inverter? The difference in cost between the two is significant so this is an important question.
- What size inverter do I need?
- Do I want my inverter to act as a battery charger also?
- Do I want to integrate my inverter into my RV’s existing AC wiring or just plug appliances directly into the inverter?
- Do I need a remote panel?
Let’s discuss each of these questions:
Do I need a pure sine wave inverter or can I get by with a modified sine wave inverter?
There are two main types of inverters, pure sine wave and modified sine wave. Pure sine wave inverters are generally 2 to 3 times as expensive as modified sine wave inverters so understanding which one you need could save you a lot of money. So what is the difference? Basically, the AC electricity that you enjoy at home from your local utility company is supplied in the form of a pure sine wave. All the electrical products sold today are designed to work off of a pure sine wave. A modified sine wave is close enough to a pure sine wave that most appliances will function fine. However, some sensitive equipment will require a pure sine wave. Therefore, it is important to determine what type of equipment and appliances you plan to use so you can determine what type of inverter you need.
........................
(Pure Sine Wave)..........................................................................................(Modified Sine Wave)
Even though most appliances will work fine using a modified sine wave, some equipment such as motors, pumps, and fans will require more power (up to 20%) and they will run hotter and longer due to the inefficiency of the modified sine wave. Therefore, if you are trying to plan the size of your battery bank along with the install of your inverter, you will need to add an additional 15-20% to account for this inefficiency. Additionally, some appliances such as radios and TVs can suffer from electrical noise with a modified sine wave inverter and some appliances can be damaged even though they seem to work fine.
The following equipment will generally work fine with a modified sine wave:
- Most household appliances
- Laptops, computers
- Cell phone chargers
- Most TVs
- Most VCRs
- Power tools
The following equipment may require a true sine wave inverter:
- Electric shavers
- Rechargeable flashlights
- High end electronics equipment (such as plasma TVs)
- Microwave ovens
- Digital clocks
- Laser printers
- Bread makers
- Light dimmers
- Some battery chargers (especially cordless tool chargers)
- Certain laptops
- Power tools using “solid state” or variable speed controls
- Some sewing machines
- X-10 home automation products
- Some medical equipment
If there is any question about whether or not the equipment you have needs a true sine wave inverter, then check with the manufacturer of the equipment or simply err on the side of caution and spend the extra money to purchase a true sine wave inverter.
What size inverter do I need?
Inverters have two important specifications that you need to take into account, the “peak” load that it is capable of supplying and the “continuous” load. Both of these specifications are rated in Watts. (Remember that you can easily calculate wattage by using the simple formula Watts=Volts x Amps). So what is the difference and why does it matter? Well, many appliances, such as appliances with motors, will require an initial surge of power to get them going (referred to as the “peak” or “surge” load). Once started, the appliance requires less power to continue running (which is referred to as the “continuous” load). A good example of this is seen in the chart below outlining the peak load and continuous load needed by various size motors.
Motor Size (in HP) |
1/6 |
1/4 |
1/2 |
1 |
Peak load |
1000 Watts |
1500 Watts |
2300 Watts |
4000 Watts |
Continuous load |
215 Watts |
300 Watts |
575 Watts |
1000 Watts |
In order to size your inverter properly, I highly suggest that you read the articles on this site related to "Estimating Power Consumption and Sizing Your Battery Bank". Additionally, you should fill out the associated Estimated Power Consumption Worksheet. Completing the worksheet will help you to determine what size battery bank you will need to power the appliances that you plan to use with your inverter and more importantly, it will force you to sit down and plan properly. Once you have the worksheet completed, you will have all the information (and electrical specifications) that you will need to take the next step.
Determining the size inverter that you need comes down to two things:
- How many total watts you will use simultaneously? (in a worst case scenario)
- What is the peak load consumed and needed by those appliances?
If you have already filled out the power consumption worksheet, then you know all the AC appliances that you plan to use in your RV or at least you have a good idea. However, chances are good that you are not going to use all these appliances simultaneously. Therefore, the next step is to determine the worst case scenario and figure out how many of these appliances you might use simultaneously. As an example, using the AC appliance chart from the article on this site, “Determining the Total Amount of Amp Hours You Will Consume,” let’s assume that you have determined that in a worst case scenario you would use all of the following items at the same time. (Remember, the inverter only supplies AC power so you only need to be concerned with the AC appliances that will be running off of the inverter.)
Sony HD Receiver = 35 Watts
Flat Panel TV = 165 Watts
Laptop Steve = 165 Watts
Laptop Amanda = 165 Watts (we like to surf the web while we watching TV)
Wireless Router = 55 Watts
Phone Charger 1 = 14 Watts
Phone Charger 2 = 22 Watts
-------------------------------------
Total = 621 Watts
Based on the calculations above, we have determined that you are going to need to purchase an inverter that can supply 621 watts of “continuous” power. My suggestion would be to purchase an inverter that can handle at least 10%–25% more. After all, your needs may change. Since I like to err on the side of caution, I would factor in an additional 25% to be safe, which means that you would need an inverter that could supply 776 watts of continuous power. Therefore, you would probably need to purchase an 800 watt inverter. However, before you can say for sure, you still need to take peak power into account and make sure that the inverter can provide the peak power that your appliances will require upon startup.
Determining peak power requirements is not an easy thing. The reason is because most manufacturers do not publish peak load requirements for their appliances. In some instances you can contact the manufacturer to obtain this information, and I encourage you to at least try. This is especially important if you are using appliances with motors since they generally require large startup loads. However, since you will most likely not be able to determine peak load requirements from the appliance’s specifications, often the best you can do is estimate. Therefore, if you need to estimate, I would suggest that you take the continuous load and multiply it by 2. So in this scenario you would estimate your peak load needs at approximately 1552 Watts (2 x 776). Be aware, however, that this simple formula is not appropriate in all cases. If you are using appliances with motors such as air conditioners, refrigerators, freezers, pumps, etc., you could require a peak load that is 3 to 5 times the continuous load rating. Therefore, if you plan to use these types of appliances, it is important to contact the manufacturer and determine the actual peak load required. For most people, using this simple estimation will suffice. If, however, in this scenario the 800 watt inverter that your were considering purchasing could not supply the necessary 1552 watts of peak power, then you either need to make some compromises or buy a larger inverter that can handle your peak load requirements.
Should I buy an inverter or combination inverter/charger?
If you have read the articles on this site relating to batteries and keeping them properly charged, then you already know that most of the chargers that are built into RVs are inferior since they are not true 3 stage chargers and can actually ruin your batteries over time. If you have determined that the charger in your RV is already a true 3 stage charger, then you are ahead of the game. If, however, you have determined that the charger that came installed in your RV is not a true 3 stage charger, now is the time to upgrade using a quality combination inverter/charger. If you choose to buy a combination inverter/charger, it will ultimately be cheaper than trying to buy both separately. Similarly, it will require fewer connections to the battery bank than it would if you installed them separately.
When the RV is plugged in or the generator is running and AC power is present, the inverter will use the available AC power to charge your batteries through the cables connected to your battery bank. When AC power is not present, the inverter will convert DC battery power into AC power for your appliances. Since the inverter is able to sense the presence or absence of AC power, this is all handled automagically. The only thing that you need to consider in this situation is the added complexity of this installation. If you want to install a combination inverter/charger, then you are going to have to connect the inverter to the AC breaker panel in your RV. This requires a certain level of knowledge about AC wiring, adding circuit breakers, using the correct sized wiring, being able to determine if your AC circuit breaker can handle the additional load, etc. Therefore, taking this extra step adds a level of complexity that may make this option too difficult for some people to consider or worst case may require you to pay a professional to complete the install.
Should I integrate my inverter into my existing RV AC wiring?
This is a question that only you can answer and will depend on how often you use your RV and for what you plan to use your inverter. Inverters come in all sizes and configurations. You can buy a simple inverter that connects to your battery bank and has AC outlets on the side that you plug your appliances into or you can buy a more advanced inverter that allows you to run electrical circuits off of it to multiple AC outlets just like your home. Just remember that if you decide to connect your inverter to the existing AC wiring, you will most likely be voiding your warranty should something go wrong.
Do I need a remote panel?
Once again, this is a question that only you can answer. If you are purchasing a high end inverter and you are planning on integrating it into your existing RV AC wiring, then I would recommend a remote panel. The remote panel will let you monitor the inverter and will provide other conveniences like being able to turn the inverter on and off. If your inverter is tucked away in a basement compartment like mine is, this is a handy feature to have.
