My homelab consists of 4 machines currently. When choosing them I tried to be energy conscious - using hardware which would not consume too much electrical power, while still trying to maintain the up-front cost low. These are mostly older systems and I was unable to find decent power consumption numbers for them.
The specs
1x MSI Cubi 3 Silent NUC
| CPU | Dual-core i5-7200U |
| RAM | 2×16GB |
2x Lenovo ThinkCentre M910 Tiny
| CPU | Quad-core i5-6500T |
| RAM | 2×8GB |
1x Mostly second-hand NAS
| CPU | Quad-core i5-4590T |
| RAM | 2×8GB |
| Motherboard | MSI H81I-S01 |
| PSU | Silverstone ST30SF 300W |
| Storage | 4x2TB SSD - mixed, Samsung EVO 870 & Crucial MX500 |
The setup
Since these are all currently plugged into shelly smart plugs, I’m able to tell the power usage of each of them separately. The plug measures the power consumption and reports that to EMQX via MQTT. From there, I have a custom prometheus collector implemented. It subscribes to the relevant topics on EMQX, and exposes a /metrics endpoint in the prometheus exposition format. This is periodically crawled by netdata, which is running in the same cluster.
I created a dashboard in netdata which allows me to visualize the CPU usage of each machine and its power consumption. It looks something like this:
I’m not going to measure the consumption of the systems when they are idle as there are quite a few things running on my cluster and I wouldn’t like to interrupt them. However, I’ll show the current CPU usage and the power draw from the plug. The CPU usage is what I’d call steady in my homelab, it rarely spikes and seems to be pretty consistent across the board. We’ll call this the baseline.
I’ll then do a 10 minute stress test using the stress tool on each machine, to see what the power consumption looks like at that moment.
The results
Note that the CPU % shows the % of cpu used across all cores - 100% indicates that all cores are working at their max. The cost estimates assume a price of 0,211479 €/kWh - coming directly from my last bill and I’ll call 30 days a month.
Here are the results for the baseline:
| System | CPU % | Power Draw | Estimated Monthly Cost |
|---|---|---|---|
| Cubi | 27% | 12.4W | €1.89 |
| Lenovo M910 Tiny | 8% | 7.3W | €1.11 |
| NAS | 4.5% | 21W | €3.20 |
And for the full load test:
| System | CPU % | Power Draw | Estimated Monthly Cost |
|---|---|---|---|
| Cubi | 100% | 17.7W | €2.70 |
| Lenovo M910 Tiny | 100% | 29.4W | €4.48 |
| NAS | 100% | 39.9W | €6.08 |
Thanks for reading!