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Boiling water in a kettle is something almost all of us do, so much that we take it for granted. We just put water in and wait for it to boil. But if you use solar power every watt counts, so what inverter size do you need to run a kettle every day?
Because inverters are not 100% efficient, you need a 1000 watt inverter to run an 800-850 watt kettle. If your kettle is at or over 1000 watts, a 1500 watt inverter is the most ideal.
How to Calculate Kettle Inverter Requirements
Electric kettles come in different sizes and types. Some use less than 1000 watts while others consume up to 2500 watts. Power consumption also depends on how much water you are boiling and its starting temperature.
Most kettles need 800 to 1000 watts to run, with higher capacity models requiring more than 2000 watts. To get the right inverter size, use this simple formula:
Total kettle watts + 20% = inverter size
If your kettle uses 800 watts, it needs a 1000 watt inverter. A good choice would be the Krieger 1100W Dual Power Inverter as it has more than enough capacity. If it is a 1000 watt kettle the inverter must supply 1200 watts and so on. You can make it higher than 20% but not less, as you risk the system running low on power.
However you need to bear in mind that kettles are not run continuously. It might need 1000 watts to start, but that does not mean it will use 1000 watts an hour. Here’s an example.
On average, a kettle can boil 1.5 liters of water in 3 minutes. Let us do the math. If the kettle uses 1000 watts an hour but you run it for only 3 minutes, that is 60 to 65 watts only.
- 1 hour = 1000 watts
- 30 minutes = 500 watts
- 15 minutes = 250 watts
- 7 minutes = 125 watts
- 3 to 4 minutes = 60-65 watts
This is a very simplified calculation. A lot of factors have to be considered such as the water temperature when you start boiling, the capacity, kettle efficiency and the inverter cable length. .
But it does give you an idea of how much power your inverter must supply. Even if your kettle requires more watts, just replace the numbers above with your own figures and divide the watts by the operating time.
In this example we assume a boiling time of 3 minutes for 1.5 liters of water. Older kettles require more time to boil water, consuming more power in the process.
Some older models may need up to 4 minutes to boil 1.5 liters of water. These usually consume 2000 to 2400 watts so total usage will be 100 watts or more. If you want to cut costs, you have to use an energy efficient kettle.
How Long Can My Inverter Run a Kettle?
Your inverter can run a kettle – or any appliance – for as long as there is power available to it. Watts consumption of any device connected to the inverter must also be below the stated inverter capacity to offset its inefficiency.
If an inverter has a 1000 watt capacity, the largest kettle you should use is 850 watts. If it is a 2000 watt inverter, the maximum kettle power draw must be 1500 watts. The reason for this is inverter efficiency, which prevents it from drawing maximum power.
Pure sine vs. Modified sine Inverter. Pure sine inverters are more effective than modified sine and are perfect for appliances, motors and electronic devices. But a modified sine inverter will run a kettle fine. For appliances with more advanced designs, use a pure sine inverter.
What is Inverter Inefficiency?
First we need to explain how an inverter works. In a solar power system, the inverter turns solar energy (DC) into AC, which is compatible with most home and kitchen appliances.
Once the inverter has converted the current stored in the battery into AC, your appliances can run. During the conversion some energy is lost. An inverter with an 85% efficiency rating means up to 15% energy / watts cannot be used. However newer inverters have reduced inefficiency to less than 10%.
This is why you should never use a 1000 watt kettle on a 1000 watt inverter. The system might start but after a few minutes it will shut down due to lack of power.
This rule is applicable to any device you want to run on an inverter. Always check the efficiency rating first. Even if you don’t intend to use the kettle much, running it at the limit might cause damage. This is particularly true for power hungry appliances and power tools.
How Many Batteries Do I Need to Run a Kettle?
In an off the grid solar system, the inverter draws power, or amps from the battery bank. The battery is run by your solar panels or another power source.
A 1200 watt kettle requires a 200ah 12V lead acid or 100ah 12V lithium battery to start. Because kettles only run for a few minutes at a time, it will not put a lot of strain on the battery. However there should be no other load running while the kettle starts.
Most RVers and homes use lead acid deep cycle batteries, as it is cheaper and more widely available. There are disadvantages though like needing regular maintenance to make the batteries last longer. Different types are available like gel, AGM, FLA and SLA, but they all have a 50-70% depth of discharge.
What this means is you cannot use its entire capacity. A 100ah 12V lead acid battery has 1200 watts (12V x 100 amp hours = 1200 watts), but you should use only 50%, or 600 watts. So it is not enough for your 1200 watt kettle.
Lead Acid vs. Lithium Batteries
To run a 1200 watt kettle on your inverter, the battery has to be at least 12V 200ah like the Renogy Deep Cycle AGM. This battery can hold 2400 watts, so even if you only use half, it is sufficient for a kettle. If you have a 1500 watt kettle, you need a 300ah battery:(300 x 12 = 3600, 50% usable is 1800 watts).
If you are willing to spend more, you can buy a lithium battery which allows for a full discharge. However it is not practical for most people especially if you only need to use a kettle. This also brings up another matter, how many electronics you will use with the kettle.
The sample figures given here are for the kettle only. If you are going to fire up a blender or heater at the same time, your inverter and battery must provide sufficient power. You might get by though because you will only run the kettle for a few minutes, but having more power is recommended.
Just like inverters, batteries should not be used to their maximum capacity. Aside from the depth discharge limit, batteries lose power faster when more amps are drawn. If you draw 5 amps from a standard 12V deep cycle battery, it should last about 20 hours. But if you draw higher amps, the battery discharges faster.
Can I Use Solar Panels For My Kettle?
Grid tied solar power systems do not need batteries because they have access to grid power. However it is possible to power a kettle with solar panels.
To run a 1200 watt kettle you will need 5 x 300 watt solar panels. Theoretically each panel can generate 1500 watts an hour combined. But that assumes each produces the maximum output of 300 watts an hour, which is unrealistic. Even if the total is less than 300 watts per hour, the five should be enough for a kettle.
Unless stated otherwise, assume the kettle runs on AC power so you still need an inverter. You can connect an inverter to solar panels. There should be no issues using the kettle unless clouds suddenly cover the sun.
With batteries you do not have to worry about the power going out while boiling water. As long as there is sufficient power available your appliances will run continuously. But if it is sunny outside you can rely on solar power too.
The amount of power required by an electric kettle might be surprising. But it is something we don’t usually think about until every watt starts to matter, which is the case when you use solar power. Fortunately we only use it for a few minutes so usage is not as high as it could be.