I have been interested in knowing the power usage of my 2019 iMac. My interest is to build a "real sinewave" inverter backed by a battery bank to power the iMac throughout a power cut. This is because of fears that the USD crisis in Sri Lanka coupled with the lack of investment in new power stations could lead to power cuts that could last 12 hrs/day.

My online research led me to this Apple forum post, I noticed the following details:

• Power consumption @ idle: 71w
• Power consumption @ CPU max: 262w
• Thermal @ idle: 242 BTU/h
• Thermal @ CPU max: 895 BTU/h

I am not using CPU max, nor am I at idle. So I wanted to check the power consumption against my day to day usage to make an accurate prediction of the specifications of the battery pack I need to build. I used a power meter I obtained through Daraz (an AliExpress subsidiary in Sri Lanka).

Configuration

My machine has the following configuration

• Model: iMac 2019 27"
• Processor: Core i9 9900KF
• RAM: 64GB
• VGA: Radeon Pro 580X (8GB)
• Storage: 1TB internal + 2TB USB-C

Power Use

Please note that these numbers are obtained by manually observing a power meter connected to the power outlet.

Power Up: The power-up process takes up to 190w. The power usage drops to about 70w when it reaches the login screen. Once you log in, the power use remains around drops to about 40w.

Idle with no apps: Once the computer loads all applications, it throttles down to about 35w and remains at that level.

Web browsing: I had two browser windows open with 15 tabs each. I am writing this blog post in one window and have some Alibaba and AliExpress product tabs. I had Office 365 and some freelance work-related browser-tabs open in the other window.

Web Development: I use nvim as my primary editor in a tmux window. I was working on a new feature for this site. It had the Rails server running along with Tailwind CSS JIT, Resque. The power usage momentarily peaks at 65w and drops to 50w when coding. When idle, the power usage is about 40w.

YouTube: I often stop working and look at YouTube videos like Tutorials. Shopping coding and opening YouTube video in FHD (in Cinema mode).

CiV6: Civ6 is the only game in my system. At the early stages of the game, the machine consumed about 150w, and towards the conclusion of the game, it reached about 200w of power.

Conclusion

Honestly, I expected higher power consumption for my software development workloads. The maximum I noticed was 65w, but the average was about 50w. I was going to pay extra for a larger than required battery pack.