If a room is cold and so you dread getting out of bed to the cold, or it is the bathroom in your case, then a low-power heater, such as a 400-watt heater may be just what you need.

*But how much electricity does it use and what will be the likely impact on your electricity bill?*

In this post, you’ll find out how much electricity the heater uses on an hourly, daily, and monthly basis. You’ll also learn how to further minimize its electricity consumption.

## How Much Power (watts) a 400 watt Heater Uses

Nearly all electric power supplied to the electric heater is converted to heat! So, its power consumption is 400 watts at 110V for a 110V/120V version.

### How Much Does It Cost to Run a 400 Watt Heater for 24 Hours

**Daily Energy Use and Cost**

The heater uses **9,600 watts per hour or 9.6 units** of electricity a day (when running continuously at maximum power).

The heater will add about USD 1.15 a day to your electricity bill. This assumes it is running at maximum power moreover continuously** for 24 hours**.

This is based on an electricity tariff of 12 cents per kWh.

*The calculation*

*Daily energy costs = 400 watts x 24 hrs = 9,600 watts or 9.6kWh. At 12 cents per kWh, the running cost of a heater is USD 1.15 from 0.12 USD x 9.6 kWh.*

*You may also be interested in this post: How much electricity a 500-watt space heater uses*

### The Cost of Running the Heater per Hour

At 0.4kwh, a 400-watt heater costs up to about **4.8 US cents** to run per hour **(0.4 units an hour)**.

Hourly energy costs are calculated as follows:

*400 watts x1 hrs = 400 watts or 0.4kWh. At 12 cents per kWh, the running cost of a heater is USD 0.048 from 0.12 USD x 0.4 kWh. *

### The Cost of Running the Heater per Hour

A 400-watt heater costs up to about **USD 34.6 a month to run** assuming it is run at maximum power for 24 hours every day for a month, using **about 288 units** of electricity.

This assumes an electricity tariff of 12 cents per kWh. This is from 400 watts x 24 hours x 30 days x 12 US cents.

*You may also be interested in: How expensive it is to run a 1,000-watt heater?*

### Is Expensive to Run?

It costs about $1.15 a day to run a 400-watt heater. This assumes it is running continuously. **Note:** Several models do not have a thermostat and will therefore not cycle on and off.

400 watts of power is about the same power that 10 x 15′ laptops draw at maximum power – full brightness and sound level at the maximum.

If it is being drawn from a battery then it can drain say a 200Ah AGM battery in about **3 hours**.

### How Many Amps the Heater Draws?

A 110V, 400-watt heater draws about **3.63 amps** at maximum power.

## How Much Space a 400 Watt Heater Heats

It is suited to heating space spaces such as an office, bedroom, or other usually up to **100 sq. ft.**

** Note: Always check your heater’s owner manual for the space it is suited to heat before buying it.*

**Related Questions**

## How Long Will a 12 Volt Battery Run a 400-watt Heater?

It depends on the battery capacity. For instance, when connected to a 200Ah, 12V AGM battery through an inverter, the 500-watt heater will run for **about 3 hours** before draining the previously fully charged battery to 50% of its capacity.

With a 100Ah AGM battery, expect the heater to run **for about 1.5 hours** before the battery is drained to 50% of its capacity (maximum recommended).

## Final Word

You can expect a 400-watt heater to consume about 9.6kWh of electricity a day if running continuously at full power.

Estimated daily and monthly energy bills when using the heater at full power assuming it is being run continuously are USD 1.15 and USD 34.6 respectively.

This assumes an electricity tariff of USD 0.12 per kWh.

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