The inverter size calculator takes the guesswork out of choosing the right inverter. Simply select your appliances below, and you’ll instantly see the inverter size you need.
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Minimum Inverter Size
Great Value
Premium Option
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Maximum Inverter Size
Great Value
Premium Option
Standard 12v models top out around 3000w (24v/48v ~ 4000w). To proceed:
- Run fewer devices at once;
- Switch to lower-wattage or DC alternatives;
- Use heavy loads only on shore power;
- Upgrade to a higher-voltage system (24 V/48 V) for a larger inverter.
Standard 12v models top out around 3000w (24v/48v ~ 4000w). To proceed:
- Run fewer appliances at a time;
- Use lower-wattage or DC options;
- Only run heavy loads on shore power;
- Consider a higher-voltage system for a bigger inverter.
How the Calculator Works
- Pick your appliances. Use the dropdown to add common devices—or enter your own custom items.
- Minimum Inverter Size: The smallest inverter that can handle your highest-wattage appliance. Ideal if you run one device at a time – or several devices whose combined draw never exceeds that of your largest appliance.
- Maximum Inverter Size: The inverter size required to run all your listed appliances at the same time. Great for full flexibility without worrying about overloads.
- Our Recommendations For each result we suggest two models – a Great Value option and a Premium option – matched to your needs.
- Not sure which to choose? Picking an inverter just above your “minimum” gives you extra headroom without too much extra cost or battery drain.
Check the appliance itself, the manual, or manufacturer’s website. Wattage should be clearly stated. If you only have the appliance’s amps, use the calculation: Watts = Volts × Amps where volts is your leisure battery voltage.
Yes. Include appliances like hairdryers, kettles, or air fryers—even if infrequently used—to ensure the inverter handles the maximum load you might need.
Inverters add load to the electrical system, even with no connected appliances. The larger the inverter, the greater the base load. So, it’s a complete waste to install an oversized inverter for your needs. The smallest size inverter is one that can run your most powerful AC with no other load.
The maximum size inverter assumes all the devices you’ve listed will be used at teh same time. If that’s the case for your setup, only enter the devices you’ll use concurrently. Make sure to include the most powerful device if it’s bigger than the combined watts of the other appliances.
Pure sine wave inverters are safer for modern electronics. Most manufacturers of inverters for RVs and campervans only supply pure sine wave inverters these days.
Do I Need an Inverter?
It depends on what appliances you want to use in your campervan:
- Only DC appliances? If you’re running everything off 12v (lights, fans, USB chargers, etc.), no inverter needed.
- Want to use AC gear off-grid? To power household AC items (microwaves, laptops, kettles) from your battery, you do need an inverter.
- AC gear only on shore power? If your AC appliances only ever run when you’re plugged into mains hookup, and they draw straight from shore power – no inverter required.
- AC gear only on shore power but through the battery? If your AC appliances only ever run when you’re plugged into mains hookup, but they still draw their power from the battery you do need an inverter.
- Need shore-power charging too? Look at an inverter-charger, which combines both inverter and battery charger in one unit for a cleaner, simpler setup.
Why the Correct Inverter Size Matters
Choosing the right inverter size is essential for efficient and trouble-free power on the road. Your inverter converts your battery’s DC power into the AC power that appliances use. Getting this size right directly impacts how smoothly your electrical setup works.
- If your inverter is too small, your appliances either won’t run or will cut out when you try to use them. For example, attempting to run a 1500w induction hob on a 1000w inverter won’t damage the inverter, but the hob won’t even start.
- If your inverter is too large, you’ll waste valuable battery capacity, money, and space. Large inverters consume extra power even while idle, increasing your battery drain. For example, using a 3000w inverter to power only small items like laptop chargers or games consoles, regularly wastes precious battery capacity and can reduce the lifespan of your battery bank.
The ideal inverter size matches your real-world usage. It should run your largest appliance with room to spare, without going excessively beyond your actual needs.
Practical Inverter Size Limits
Inverters and AC appliances are inherently power-hungry and can quickly drain batteries. A 1000w inverter fully loaded for one hour will draw around 90 amps from a 12v battery. To replenish those 90 amps, you’d need about 300w of solar panels receiving 4 good hours of sun. Remember, you can only take out of your battery what you put in.
Inverters for standard 12v campervan systems typically max out around 3000w. Manufacturers rarely produce larger models due to battery drain and wiring complexity. Similarly, 24v and 48v systems generally support inverter sizes up to about 4000w.
If your inverter size exceeds these practical limits:
- Reduce how many appliances uses at the same time.
- Consider lower-wattage appliances or DC alternatives.
- Use high-demand appliances only when connected directly to shore power.
- Check if upgrading your electrical system voltage (24v or 48v) is practical.
Being realistic about inverter limits ensures a safe, efficient campervan electrical system.
Common Mistakes to Avoid When Sizing Your Inverter
Overaccounting for Appliance Startup Surges
Appliances like induction hobs, microwaves, and refrigerators briefly use more power when first switching on. Some people assume this means selecting a significantly larger inverter, but that’s often unnecessary.
Good-quality inverters already handle these brief surges comfortably. For instance, a typical 2000w inverter easily manages short-term surges up to around 4000w.
✅ Tip
Always check your inverter’s surge rating to ensure it comfortably meets your appliance’s startup demands.
Oversizing Your Inverter “Just in Case”
Picking a larger inverter “just in case” usually backfires. It costs more up front, drains your battery faster, and takes up precious campervan space.
💡 Better approach
Include any future appliances in your device list. The calculator will then size your inverter to handle that full combined load from the start – so you never have to upgrade later.
Underestimating Your Actual Power Needs
Avoid guesswork or rough estimates for your power consumption. Getting this wrong could leave you with either an inverter that’s too small – causing frequent power interruptions – or an excessively large inverter that unnecessarily drives up costs.
🔧 Easy Fix
Use our inverter size calculator to accurately determine your power needs based on your real-world usage.
Misunderstanding Inverter Efficiency Ratings
There’s often confusion around inverter efficiency, but it’s straightforward. A 1000w inverter is designed to run appliances rated up to 1000 watts. Manufacturer’s already factor in the inverter’s internal efficiency, so you don’t need to select a larger inverter than your total wattage demand.
Bottom line – trust manufacturer ratings – they accurately represent real-world capabilities.
🛠️ Beyond the Inverter: Complete Electrical System Design
Choosing an inverter is key, but it’s only one piece of your campervan’s power system. Our custom design service takes care of everything – batteries, chargers, wiring, and more.
In minutes, you’ll fill out a quick form and get back a full electrical design:
- A wiring diagram
- A complete parts list
- Detailed, easy-to-follow notes
It’s all tailored to your van and lifestyle – no guesswork or headaches. Let us handle the technical side so you can enjoy a fully integrated system.
