How to Size Your 12V Power Inverter (Free Inverter Sizing Calculator)
How to Size Your Off Grid Power Inverter [Free Calculator Inside]
Reading time: 4 minutes
This guide will walk you through everything you need to know to select the perfect sized inverter for your needs. If you’re in a hurry, just use our free inverter size calculator below!
When shopping for inverters, you'll encounter two important power ratings. For example, you might see an inverter rated as "1000W/2000W". Here, 1000W is the continuous power rating, while 2000W is the peak power rating.
1. Continuous Power Rating: This is the amount of power your inverter can reliably provide for regular, day to day use.
2. Peak (or Surge) Power Rating: This indicates the maximum power the inverter can supply for short bursts, typically just a few seconds.
💡 Voltanic Tip #1: Focus primarily on the Continuous Power Rating, as this represents the inverter's actual capacity for general daily use. The Peak Power Rating is important for handling short-term surges but should be a secondary consideration.
Caution: Marketing Tactics
Be aware of potentially misleading marketing, especially on platforms like eBay. Some sellers emphasize peak power ratings to make their products seem more powerful. Always:
Double-check specifications before purchasing
Be skeptical of deals that seem too good to be true
Choose inverters from reputable sellers and brands such as these wonderful inverters below 😉
Step #2: Match Inverter Voltage to Battery Voltage
Other than wattage, an inverter will be rated for 2 voltages: Input & Output Voltage. It's crucial to ensure that the inverter's input voltage matches the voltage of your battery. For example, if your system uses a 12V battery, you will need a 12V inverter.
Input Voltage (DC)
This is the voltage coming from your batteries into the inverter. Common input voltages are:
12V: Used in 90% of small systems (motorhomes, campers, sheds)
24V: Often used in medium-sized off-grid systems (static caravans)
48V: Common in larger residential and commercial systems
Output Voltage (AC)
It's unlikely you need to worry about selecting the right output voltage as it will most certainly be standardized for the country you are in. In the UK, the output voltage is standardized at 230V, which is the voltage that comes out of your 3-pin sockets & that powers your appliances.
230V: Used in the UK, Europe, Australia, and many other countries
120V: Standard in North America, parts of South America, and Japan
💡 Voltanic Tip #2
In the UK, you may see both 240V and 230V advertised. They are effectively the same, as the actual supply typically ranges from 216V to 253V due to permitted tolerances.
If you're unsure what voltage your system is, check your battery's label or google the model number. If you're still unsure, send us a message and we'll be happy to help.
Step #3: Calculate Your Power Needs
Now it's time for a bit of Mathematics. To calculate what size inverter you need, follow these steps:
1. List all the devices you plan to power:
Fridge, Microwave, Kettle
TV, Laptops, Phones
Hairdryer
Lighting
Waterpumps
2. Check the power consumption of each device:
Check labels or manuals for 'output power consumption' in watts
If only volts & amps are provided, use the formula: Volts x Amps = Watts
3. Consider simultaneous usage: Determine which devices you'll use at the same time.
4. Calculate Total Wattage: Add up the wattages of simultaneously used devices.
Add a 20% safety margin as you don't want to operate at the maximum: 1300W + 260W = 1560W
In this example, you should look for an inverter rated at least 1560W for continuous power.
💡 Voltanic Tip #3: If you will be regularly using high powered devices (like a 1500W drill), you might want to consider oversizing (3000W rather than a 2000W for example) as operating at the maximum capacity for extended periods will reduce the inverters lifespan (kind of like driving a car at maximum speed 24/7)
Frequently Asked Questions
What Size Inverter for a Campervan? For a typical campervan, a 1000W to 2000W inverter is often sufficient. This can run essentials like a TV, laptop, and small kitchen appliances
Will a 1000W Inverter Power a Kettle? Most electric kettles require 1500W-2000W, however you can find travel/camping kettles on ebay & Amazon which output around 900W. Piece of advice, unless you like lukewarm cups of tea, do not buy a 12V kettle!
What Size Inverter to Run a Microwave? Microwaves usually require 1000W-1500W. A 2000W inverter with a high surge capacity should be sufficient for most microwaves.
What Size Inverter to Run a Fridge? A typical refrigerator needs 150W-400W to run, but may require up to 1200W to start. A 1500W inverter with a 3000W surge capacity should handle most refrigerators.
What Size Inverter Will Run a House? For a whole house, you typically need a 5000W-10000W inverter, depending on your power needs. Larger homes or those with high-draw appliances may require even more capacity.
Battery Considerations
The size of your battery bank is just as important as your inverter size. Here are some common questions:
How long will a leisure battery last with an inverter? This depends on the battery capacity and inverter draw. For example, a 100Ah battery might run a 1000W inverter for about an hour.
Can you run an inverter off a leisure battery? Yes, but ensure the battery can handle the inverter's power draw.
What size inverter for a 100Ah lithium battery? A 1000W-1500W inverter is typically suitable, but it depends on your specific power needs.
If you made it this far great! You should have all the knowledge you need to select the right sized inverter for your off-grid setup.
If you still need advice, just send us a message and we'll be happy to help!
Check out our other blogs for more expert guidance
How to Size Your Off Grid Power Inverter (Free Calculator Inside)
How to Size Your Off Grid Power Inverter [Free Calculator Inside]
Reading time: 4 minutes
This guide will walk you through everything you need to know to select the perfect sized inverter for your needs. If you’re in a hurry, just use our free inverter size calculator below!
Inverter Size CalculatorStep #1: Understanding Inverter Ratings
When shopping for inverters, you'll encounter two important power ratings. For example, you might see an inverter rated as "1000W/2000W". Here, 1000W is the continuous power rating, while 2000W is the peak power rating.
Caution: Marketing Tactics
Be aware of potentially misleading marketing, especially on platforms like eBay. Some sellers emphasize peak power ratings to make their products seem more powerful. Always:
1200W Pure Sine Wave Inverter | 12V DC/AC
£155.00
2000W Pure Sine Wave Inverter | DC/AC
£240.00
3000W Pure Sine Wave Inverter | DC/AC
£330.00
Step #2: Match Inverter Voltage to Battery Voltage
Other than wattage, an inverter will be rated for 2 voltages: Input & Output Voltage. It's crucial to ensure that the inverter's input voltage matches the voltage of your battery. For example, if your system uses a 12V battery, you will need a 12V inverter.
Input Voltage (DC)
This is the voltage coming from your batteries into the inverter. Common input voltages are:
Output Voltage (AC)
It's unlikely you need to worry about selecting the right output voltage as it will most certainly be standardized for the country you are in. In the UK, the output voltage is standardized at 230V, which is the voltage that comes out of your 3-pin sockets & that powers your appliances.
Step #3: Calculate Your Power Needs
Now it's time for a bit of Mathematics. To calculate what size inverter you need, follow these steps:
Example Calculation:
Kettle (1000W) + Refrigerator (150W) + Lights (50W) + TV (100W) = 1300W
Add a 20% safety margin as you don't want to operate at the maximum: 1300W + 260W = 1560W
In this example, you should look for an inverter rated at least 1560W for continuous power.
Frequently Asked Questions
What Size Inverter for a Campervan? For a typical campervan, a 1000W to 2000W inverter is often sufficient. This can run essentials like a TV, laptop, and small kitchen appliances
Will a 1000W Inverter Power a Kettle? Most electric kettles require 1500W-2000W, however you can find travel/camping kettles on ebay & Amazon which output around 900W. Piece of advice, unless you like lukewarm cups of tea, do not buy a 12V kettle!
What Size Inverter to Run a Microwave? Microwaves usually require 1000W-1500W. A 2000W inverter with a high surge capacity should be sufficient for most microwaves.
What Size Inverter to Run a Fridge? A typical refrigerator needs 150W-400W to run, but may require up to 1200W to start. A 1500W inverter with a 3000W surge capacity should handle most refrigerators.
What Size Inverter Will Run a House? For a whole house, you typically need a 5000W-10000W inverter, depending on your power needs. Larger homes or those with high-draw appliances may require even more capacity.
Battery Considerations
The size of your battery bank is just as important as your inverter size. Here are some common questions:
If you made it this far great! You should have all the knowledge you need to select the right sized inverter for your off-grid setup.
If you still need advice, just send us a message and we'll be happy to help!
Check out our other blogs for more expert guidance
Inverter Size Calculator