What is the minimum wattage of PSU ?.

Building a Core XY which is going to have a 220v mains heated bed , I've purchased a 500 watt 24 volt psu , but don't think I will use it because it will finish up be the loudest part .
For it is not going to power the heated bed thinking of getting something like a 200250 watt fan free like this one https://ooznest.co.uk/product/250wpowersupply/ what is the power usage of a 3d printer a couple of amps for the motors and a 40w heater cartridge ? 

O.K
Bed heating power: 0.0 watts
Extruder heater power: 40 watts
Stepper motors: at full rated current, 1.68A * 5 * 24v = 201 watts add 50% 300 watts.
plus 10 watts for the fan and the duet it's self .360 watts for the motors , extruder heater and fans/board look a bit high to me.

@peter247 said in What is the minimum wattage of PSU ?.:
Stepper motors: at full rated current, 1.68A * 5 * 24v = 201 watts add 50% 300 watts.
That part is wrong. Read the page I linked to again.

@dc42 Stepper motors: at full rated current, the power needed for each motor is its rated current times its rated voltage (if no rated voltage is specified, use the square of the rated current times the phase resistance). This is the power at standstill. To allow for driver losses and the extra power needed to create acceleration, add 50%.
Multiply by the number of stepper motors.The power needed for each motor is its rated current times its rated voltage 1.68A * 24 volt = 40.32 watts per motor.
To allow for driver losses and the extra power needed to create acceleration, add 50%. 40 watts + 50% = 60 watts per motor
Multiply by the number of stepper motors * 5 = 60 * 5 = 300 watts

@peter247 said in What is the minimum wattage of PSU ?.:
The power needed for each motor is its rated current times its rated voltage 1.68A * 24 volt = 40.32 watts per motor.
The rated voltage of those stepper motors is not 24V.

https://e3donline.com/collections/motors/products/motors
For I'm using the High Torque Motor which doesn't say a voltage I square the current and times the phase resistance.
phase resistance = 1 ohm , but not idea what it is .
motor current = 1.68 ampsSo 1.68 squared * phase resistance ( 2.8 * 1 ) + 50% * 5 motors ?
That looks more sensible and not into 100s of watts .

@peter247 said in What is the minimum wattage of PSU ?.:
https://e3donline.com/collections/motors/products/motors
For I'm using the High Torque Motor which doesn't say a voltage I square the current and times the phase resistance.
phase resistance = 1 ohm , but not idea what it is .
motor current = 1.68 ampsSo 1.68 squared * phase resistance ( 2.8 * 1 ) + 50% * 5 motors ?
That looks more sensible and not into 100s of watts .
Yes, that looks right.

@peter247 said in What is the minimum wattage of PSU ?.:
E3D used to provide much more detailed info on their motors with a model number and data sheet. Not sure why they changed it.

@phaedrux Looking at your machine , MeanWell SE20024V passively cooled PSU.
What is the SE , can see people selling the Meanwell RSP20024 200W 24V Active PFC Enclosed Power Supply , but the SE look to be on aliexpress . 
Check digikey or mouser for MeanWell supplies.
The particular PSU I'm using may be discontinued at this point I think, but likely replaced by something similar. Perhaps the RSP is that.
https://www.mouser.ca/ProductDetail/MEANWELL/SE20024?qs=erfQA2AIGbXP8MZzK7SQeA==
Yes it's marked obsolete, and have a replacement linked.
https://www.mouser.ca/ProductDetail/?qs=ah3jBNVE1PQukNhKX3jUsA%3D%3D

@phaedrux The LRS20024 looks to be a little cheaper than the rsp model , but I guess that depends who you get it from.
Thank you , I'll try to get a LRS20024 , who need a noisy fan when you can passively cool it.

@peter247 said in What is the minimum wattage of PSU ?.:
but I guess that depends who you get it from.
Keep in mind that mouser and digikey usually have free shipping and a warranty, and you're sure to be getting what you pay for.