Most people choosing colocation know their server’s size in rack units (U). Far fewer know how much power it uses, and power is usually what sets the price and the plan.
It gets more confusing across borders. Providers in the US and Canada often quote power in Amps, while many UK providers quote kilowatts. The same “1 Amp” also means a different amount of power in each country.
This guide explains the units, shows how voltage changes the numbers in the US, Canada and the UK, and walks you through estimating your own server’s power consumption. Supreme Servers offers Colocation in Miami, Dallas, Silicon Valley, Toronto and the UK, so we size power in all three countries. Already know your hardware? Start with the calculator below.
Server power calculator
Work out how many Watts and Amps your servers need for colocation. Pick your location, add your equipment and see how much power to ask for.
Don’t know the Watts? Power supply rating ÷ 3 is a fair estimate. A reading from iDRAC, iLO or IPMI is better.
Total draw
0 W
With headroom
0 W
Ask for
0 A
See how much power to ask for
Enter your name and email to unlock your results.
By clicking See my results, you agree that Supreme Servers may contact you about your Colocation needs. See our Privacy Policy.
What do Watts, Amps and Volts mean?
You only need five terms to read any colocation quote.
| Term | What it means | Example |
|---|---|---|
| Watts (W) | How much power a device uses at a given moment | A small 1U server might use 100W |
| Kilowatts (kW) | 1,000 Watts, used for racks and larger setups | Ten 300W servers = 3 kW |
| Volts (V) | The "pressure" of the electrical supply, set by the country and circuit | 120V, 208V or 230V |
| Amps (A) | How much current flows. Amps depend on the voltage | 1A at 120V = 120W |
| Kilowatt-hours (kWh) | Energy used over time, what a utility bill counts | 1 kW running for 24 hours = 24 kWh |
The one formula to remember
Watts = Volts × Amps
So Amps = Watts ÷ Volts. Modern server power supplies are efficient enough that this is close enough for sizing a plan.
Most colocation plans give you a power allowance (in Amps or Watts) rather than billing every kWh. Your job is to make sure your servers fit inside that allowance with room to spare.
Why does 1 Amp mean different power in the US, Canada and the UK?
Because the voltage is different. One Amp in the UK delivers almost twice the power of one Amp on a standard US or Canadian 120V circuit. That is why comparing "Amps" between countries without checking the voltage gives the wrong answer.
| US | Canada | UK | |
|---|---|---|---|
| Common rack voltage | 120V or 208V | 120V or 208V | 230V |
| Three-phase supply | 208V | 208V (buildings may also have 600V) | 400V |
| Power from 1 Amp | 120W at 120V, 208W at 208V | 120W at 120V, 208W at 208V | 230W |
| Amps for a 300W server | 2.5A at 120V, 1.4A at 208V | 2.5A at 120V, 1.4A at 208V | 1.3A |
| How power is often quoted | Amps (with voltage) | Amps (with voltage) | Amps or kW |
| Usable load on a circuit | About 80% of the breaker rating under electrical code (a 20A circuit carries about 16A) | About 80% under the Canadian Electrical Code | Set by the provider; ask what is usable on a 16A or 32A feed |
What this means for you:
- In the US and Canada, always ask "Amps at what voltage?" 2A at 120V is 240W. 2A at 208V is 416W.
- In the UK, a quote of 1A is about 230W, so the Amp numbers look smaller for the same server.
- Canada and the US use the same voltages and plugs, so sizing works the same way in Toronto as in Miami or Dallas.
- Comparing plans across countries? Convert everything to Watts first. Watts mean the same thing everywhere.
How do I estimate my server's power draw?
Your server almost never uses what its power supply is rated for. A 750W power supply is the maximum it can deliver, not what the server draws day to day.
- Measure it if you can. Most servers report live power use in their management tools: iDRAC on Dell, iLO on HPE, IPMI on Supermicro. A plug-in power meter on the wall socket works too. Note the figure under a normal workload.
- No reading? Estimate from the label. A simple rule: power supply rating ÷ 3 ≈ typical draw. A 750W supply suggests about 250W in normal use.
- Count only one power supply. Servers with two supplies share the load between them. Two 750W supplies do not mean 1,500W.
- Add up every device. Include switches, firewalls and storage, not just servers.
- Add 20% headroom. This covers busy periods, startups after a reboot and small upgrades.
- Convert to your country's units. Divide the total Watts by 120 or 208 (US and Canada) or by 230 (UK) to get Amps.
Worked example
Two servers at about 250W each plus a 40W switch is 540W. With 20% headroom that is about 650W: 5.4A at 120V, 3.1A at 208V or 2.8A at 230V. Try your own numbers in the calculator.
How much power do typical servers use?
These are rough ranges for normal use, not guarantees. Your own measurement always wins. Amps are shown for the top of each range, so you plan for the busier end.
| Device | Typical draw | Amps at 120V (US, Canada) | Amps at 208V (US, Canada) | Amps at 230V (UK) |
|---|---|---|---|---|
| Firewall or router appliance | 20–60W | 0.5A | 0.3A | 0.3A |
| Network switch (1U) | 30–150W | 1.3A | 0.7A | 0.7A |
| Small 1U server, single CPU (e.g. Dell R250/R350, HPE DL20) | 40–110W | 0.9A | 0.5A | 0.5A |
| 1U or 2U server, single CPU, more drives or memory | 100–180W | 1.5A | 0.9A | 0.8A |
| Storage server with many drives | 200–500W | 4.2A | 2.4A | 2.2A |
| 2U server, dual CPU (Xeon Gold/Platinum, AMD EPYC) | 300–600W | 5.0A | 2.9A | 2.6A |
| GPU server (AI, rendering) | 1,000–3,000W+ | 25A | 14.4A | 13A |
If your hardware sits near the top of a range, or you run heavy workloads all day, measure before you choose a plan. GPU servers usually need a rack quote rather than a single-server plan.
Do I need a single server plan or a rack?
Pick the plan by whichever runs out first: rack space or power. For modern servers, power usually runs out first.
Take eight 1U servers at 500W each. They fit in 8U of space, but together they need 4 kW. That is about 33A at 120V, 19A at 208V or 17A at 230V, far more than a few single-server plans would include.
A single-server plan fits when:
- You have one server, from 1U to 4U.
- Its measured or estimated draw fits inside the plan's allowance with 20% to spare. In Miami, for example, our single-server plans include 120W for 1U, 240W for 2U and 360W for 4U.
Ask for a rack quote when:
- You have several servers, or servers plus network gear.
- Any one server is dual-CPU, storage-heavy or GPU-based.
- You expect to add hardware in the next year. Leaving power headroom now avoids a move later.
In Dallas, Silicon Valley, Toronto and the UK, Colocation is quoted to your hardware, from a single server to a full rack. Compare our data centers.
Frequently asked questions
Is my power supply's rating what I'll use?
No. The rating is the most the supply can deliver. Typical draw is often around a third of it, and a live reading from iDRAC, iLO or IPMI is better still.
My server has two power supplies. Do I need double the power?
No. Redundant supplies share the load, and either one can carry the server alone. Plan for one supply's worth of real draw.
Why do UK quotes show fewer Amps for the same server?
UK circuits run at 230V, so each Amp carries about 230W. On a US or Canadian 120V circuit, each Amp carries 120W. The server uses the same Watts in both places.
Is power in Canada different from the US?
No. Canada uses the same 120V and 208V supplies and the same plugs. A server sized for Miami or Dallas is sized the same way for Toronto.
Can I move a server from the US to the UK?
Usually, yes. Most server power supplies accept 100–240V. Check the label on each supply before you ship, and plan for different power cords.
Am I billed for every kWh I use?
Most colocation plans include a fixed power allowance in the monthly fee rather than metering every kWh. Check how your provider counts power before you compare prices.
What happens if I go over my power allowance?
You can add extra power to your plan or move up to a larger plan. If your hardware outgrows a single-server plan, we'll quote a dedicated cabinet instead.
What if I don't know my hardware's power draw at all?
Send us the make, model and workload of each device. We'll estimate the draw and recommend the right plan.
Not sure how much power you need? Get a quote
You don't have to work it out alone. Tell us the make, model and workload of each server and device, and the location you want: Miami, Dallas, Silicon Valley, Toronto or the UK. We'll size the power with you and send a Colocation quote that fits your hardware, from a single server to a full rack.
Prefer email? Write to [email protected].