americanaudiophile :
You won't hurt your PC without a UPS but plugging it into a good surge protector is not a bad idea. These also wear out with time.
These are popular myths not supported by any facts, defined by any numbers, and only found in hearsay. Best protection at a computer is already inside a computer. 'Dirtiest' power comes from a UPS in battery backup mode. Power so 'dirty' as to be potentially harmful to motorized appliances and power strip protectors. But ideal to all computers due to superior protection inside each computer.
So what does an adjacent protector do? Destructive surges occur maybe once every seven years. Many 'know' it does something because a computer/appliance has not failed for five years? What kind of reasoning is that? Worse, potentially destructive surges are typically less frequent in the UK. Where is any proof (with numbers) that a power strip does anything useful? Not posted. Even manufacturer specification numbers for a protector were not posted for one simple reason. Manufacturer does not claim such protection.
Degraded MOVs is another popular myth. Some numbers. Destructive surges are hundreds of thousands of joules. How many joules does a power strip claim to absorb? Hundreds? Near zero. An adjacent protector is grossly undersized to fail on surges too tiny to even harm a computer. That means hearsay to promote sales.
What happens when MOVs are properly sized? An MOV manufacturer describes how to test MOVs for degradation (defined as a 10% change of Vb) when properly sized:
The change of Vb shall be measured after the impulse listed below is applied 10,000 times continuously with the interval of ten seconds at room temperature.
How often do you have 10,000 surges? Listed was a number - maybe one surge every seven years. An effective protector earths direct lightning strikes and remains functional. Grossly undersized protectors degrade or fail catastrophically; promoting myths and sales.
Useful and honest replies include hard numbers. Myths are quickly identified by subjective claims (without numbers) promoted by advertising and hearsay.
Due to protection already inside computers, than all UPSes are not harmful. However a UPS is usually made as cheap as possible. Therefore its battery typically fails in three years. IOW it no longer does it only useful function. Someone Somewhere has describes how to test for this. And discusses the purpose of a UPS - protection of unsaved data.
Hardware protection from surges is provided by something completely different that has not yet been discussed.