# Rated Power Variance

I have a question about the rated power of a coffee machine.

The specs on the coffee machine are;

Rated Voltage 220-240V~50/60Hz

Rated Power Coffee Machine Only - 915-1090W Together with Milk Frother - 1372-1633W

For context this is being installed in a vehicle and being run off a 1000W 12V/240V inverter. The inverter has dip switches that let me adjust the output voltage(200,220,230,240)/frequency(50/60).

Is the rated power 'range' 912 to 1090 related to the Voltage/Frequency you have it connected to? If so does the Frequency affect it?

As I understand it Power doesn't change with Voltage (the Amps will change) therefore the 220/240 shouldn't affect it and is it then the Frequency.

Simply by setting the inverter a certain way (eg 220V/50hz) will it operate at 912W.

Apologies for the long winded question.

• Explain why setting the inverter a certain way it will solve your problem. You do not state which version of the machine you are using. From what I see you will not have a working or reliable unit. These units have motors in them, the type may have a big effect when you change the frequency.
– Gil
Commented May 20, 2021 at 4:01

The 'coffee machine' part of the rating is simply a resistive heater. This will draw power according to the square of the voltage. You can see this as the range of power drawn is 1090/915 = 1.2ish, and the range of input voltage is 240/220 = 1.1ish. Frequency does not affect this at all.

If you set your inverter to 200 V output, you would expect the heater to draw (200/220)2*915 = 750 watts. The coffee would take longer to make, but it wouldn't hammer your RV battery quite so much.

The frother, from the use of the word 'together', appears to take another 400 to 600 watts. This is very likely to be a series wound 'universal' motor. This will vary a little with frequency, and will vary strongly with the load you put on the motor, it's not a simple calculation as for the heater. Even at the lowest end of that range, it's still possible to draw more than your inverter max output if used at the same time as the heater.

Set your inverter to 200 V, 60 Hz, and switch the heater off before you use the frother.

• Thanyou. Yes the frother can clip into the side of the coffee machine, no intention of using them together. There is the pump in the coffee machine too, but the heater is clearly the larger load as the load on the battery is highest when the machine (my current one) is warming up, and then drops to about half when it is just the pump.
– Matt
Commented May 24, 2021 at 2:25

Power is Volts multiplied by Amps. Since the load will most likely be resistive heaters, the voltage also will affect the power consumed. The frequency should have little effect. Also note there is some tolerance, so given a specific voltage the manufacturer is only saying the power will be with that range.

I’d suggest you get a bigger inverter.

• Thankyou. The inverter can run at 120% for upto 60s. Most pod type machines only jump up to the maximum for a couple of seconds. The machine I currently have is an older version and is 900W. The new version has been "upgraded" to heat up faster.
– Matt
Commented May 24, 2021 at 2:19