How Many Amps Does A 3kW Immersion Heater Use? (Know It Now)

how many amps 3kw immersion heater use

The immersion water heater consists of a metal cylinder that holds water. You can flip a switch to activate the heating element, raising the temperature until the water is hot enough for you to use. You are probably wondering whether it is a trustworthy financial investment? How much energy does it use? Will it raise your utility bills or lower them?

How many Amps Does A 3kW Immersion Heater Use?

As a general rule of thumb, a 3kW immersion water heater uses 13.63A. You can use a 13A fuse with 3kW immersion heaters.

3kW Immersion Heater Amps


This doesn’t necessarily tell you whether or not immersion heaters are energy-efficient.

The Greenage expects a 3kW to cost you 45p an hour in the United Kingdom.

But that assumes that your immersion heater has a thermostat that turns the appliance off once it attains the relevant temperature. First of all, you cannot always predict the duration an immersion heater will take to raise the water to the appropriate temperature.

Some appliances will heat the water in an hour or two. But it may take others several hours, especially if the voltage keeps fluctuating or if the heating element is defective.

Secondly, some people leave their immersion heaters on permanently. They hate the idea of waiting hours for the water to heat up whenever they want to shower.

Keeping the heater on at all times ensures that the water is always warm. But this practice increases the energy consumption of the appliance.

Let Save Electricity has a calculator that shows you your energy consumption. You must enter the wattage, daily operational hours, and electrical tariff in your country.

This calculator will tell you how much power your heater uses each day, week, month, and year. People with immersion heaters have a habit of underestimating the volume of electricity their devices use.

Even though the daily cost is low, they do not realize that those pennies add up.

Why Amps Matter For Immersion Heater?

Do you know why your contractor cares about the amps the immersion heater uses? They want to ensure that your home’s circuit can accommodate the electrical needs of the appliance.

Most homes have 15A and 20A circuits. Therefore, the heater must run on those 15A and 20A circuits. But you can’t pair a 15A heater with a 15A circuit or a 20A heater with a 20A circuit.

You can only use 80 percent of the circuit’s capacity. Therefore, a 15A heater is better suited to a 20A circuit.

What happens when you add a heater with the wrong amperage to your circuit? If the appliance’s ampacity exceeds the breaker size, it will trip whenever you run the immersion heater.

In other words, it will become a nuisance. What if the breaker fails to respond? You may burn your house down. 13A is nothing to scoff at. A 3kW heater’s energy requirements can easily overwhelm smaller wires, melting their insulation.

5 Tips To Run Immersion Heater Safely

Immersion heaters are dangerous. But you can mitigate some of the threats by taking the following factors into account:

1). Wire Size

I want you to use 12AWG wire for 20A heaters and 10AWG wire for 25A. The greater the amps, the thicker the wire required.

Related Post: Can I Use 14 Gauge Wire On 20 Amp Circuit? (Or 12 Gauge)

People think the breaker size is the most important aspect of a heater’s installation, but they are wrong. The breaker size won’t matter if the wire size is incorrect.

Breakers don’t protect appliances. Instead, they defend the wires by preventing the appliances from using more electricity than the wires can handle. In the process, they protect the appliances.

But if the wires are too small, they will overheat, melt and start a fire before the breaker can react. Therefore, you have to match the wire size to the breaker size.

2). MCB Size

3 kW water heater needs 16A MCB.

PowerMCB AmpMCB Type
1 KW6 AC
2 KW10 AC
3 KW16 AC
6 KW32 AC

Miniature circuit breakers respond to overloading and short circuits. They are crucial to the safety of your home. There are several attributes you have to consider when selecting an MCB, including the breaking capacity and tripping characteristics. But the size is just as important.

3). Dedicated Circuit Or Not

Put the immersion heater on a dedicated circuit. You don’t have to. More than likely, your local regulations expect you to make the best decision for your home. They won’t force you to utilize a dedicated circuit.

However, a dedicated circuit is the safer option. You are less likely to cause an overload. Think about it. Heaters use a lot of power. If you force the appliance to share the circuit with other heavy-duty devices like freezers and washers, you may start a fire.

Even if you are too smart to overload the circuit, other people may not know better. Your friends and family may connect the heavy-duty appliances to the circuit without realizing that it has to operate a powerful immersion heater. You are better off not taking any chances.

4). Breaker Size

Match the breaker size to the heater’s amperage. If the heater uses more amps than the breaker can handle, it will trip repeatedly. If the breaker is too big, it may not trip quickly enough to prevent an overload, especially if the wires are too small.

Related Post: What Size Breaker Do I Need For Different Watt Appliances?

5). Duration

If you own an immersion heater, you might be tempted to leave it running at all hours of the day or night because you want the hot water to be readily available.

But that practice is not encouraged because it will hike your electric bill drastically. You are better off buying a timer. You should also buy heaters that can be programmed.

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