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We have a series of grey-box style computers acting as servers at my workplace (rather than rack-mount).

We were looking to get Uninterruptible Power Supplies for them. However, I'm not sure how many at what capacity are required. I'd assume it would be a good idea to hook the peripherals in as well - there's a 18.5" LCD monitor with a KVM, along with a couple of USB hard drives that require power.

I currently have the most vital machine hooked up to a cheap (temporary) UPS, but it's probably close to worse than nothing. I'm looking for reasonable value for money, though I can probably negotiate with my boss on price range. I recognise that I may well need to buy two (or even three) UPSs to support the three machines.

Any recommendations?

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up vote 3 down vote accepted

1) You need to identify your power requirements. Get a cheap power consumption monitor socket and plug it in. Write down the consumption on boot/idle/heavy load.

2) Identify how much time you want to be able to operate without power. 5 mins? 10 mins? 1 hour?

3) Browse your local hardware shop for a UPS that suits your needs.

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FWIW, I like these Kill-A-Watt Meters from P3 : only about $20 (+ shipping) – Jason Mar 31 '10 at 11:08
Or if you spot any energy-trade shows nearby go and grab one of these for free – Iraklis Jun 2 '10 at 11:48

Iraklis's answer is the right thing to do but you may be like me and not want/know how to measure the power requirements. Or maybe you don't want the blame if you get it wrong!

We just searched "Uninterruptible Power Supplies" and had a nearby company do a free site survey and quote. They were willing to sell us the UPS at a one-off reduced price or go for a maintenance contract.

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Free is good, and if a local small company is willing to work for your business, go for it! – kmarsh Mar 31 '10 at 12:33

APC ( are well respected UPS suppliers. They are popular on eBay as well if you want to try and pick one up a bit cheaper.

Iraklis asks good questions about scaling for your requirements. If you just want the system to shutdown cleanly when mains power is lost you won't need much battery life.

If you can't take the machines down to put a monitor on the power supply you could estimate power consumption of the machine. There are sites which give rough power usage per item in a machine which will help to calculate an estimate.

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First, get on of these. They are inexpensive and more than accurate enough for your needs.

Shut down a server and bring it up again on the P3 and get some idle, busy, light usage and long term statistics. The P3 has the long term tracking built-in.

Now you know how many watts your servers need. UPS's are primarily rated in VoltAmps, which are only peripherally related to the watt draw. VA has more to do with the power reserve available. In other words, one 3KVA system might be able to supply 1000W of power to clients, while another 1500W, albeit for a shorter period of time.

Next, evaluate what power you have available. It does you no good to get a 2KVA UPS with a 20A plug if you have only 15A power available.

Then, decide on your form factor, and the choices fall out pretty easily.

Once installed, don't forget installing the shutdown software and connecting the cables. Having 35 minutes of reserve power is great until you have a 40 minute power outage.

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