Guess I'll keep looking or see what other opinions I can get on the matter.
Step back a minute. If any recommendation comes without numbers, then ignore it. For example, voltage can drop so low that incandescent bulbs dime to 40% intensity. Even that is good voltage for any computer. How many advertisers will say that? None. Most only posted what advertising says; not what engineering and specification numbers say. Best is to ignore recommendations that are subjective.
Power supplies must be so robust as to convert massive AC voltage changes into rock sold, clean, low DC voltages that vary as little as 2%. So what does a UPS do for hardware? Only what is already done inside a computer. UPS is temporary and 'dirty' voltage so that unsaved data can be saved.
But if I can increase profits by hyping fears of sags, then I too would be saying something completely different.
No major appliance should cause dimming even on 1930 wiring. In most cases, that dimming is due to a loose screw holding a wire, receptacles connected using the back stab method, or wire nuts applies without first twisting copper wires together. In rare cases, that dimming indicates an impending human safety problem. But at no time does dimming create a threat to any electronics appliance.
Dimming is irrelevant to electronics. But low voltage is problematic to motorized appliances. If low voltage concerns you, then UPS should be on a dishwasher, refrigerator, and furnace.
If lights are dim are on a completely different circuit from a Dyson, then be more concerned for a potential human safety issue probably anywhere between a main breaker box and street transformer.
Read numbers on any surge protector's box. A let-through voltage of 330 means that protector ignores everything until 120 volts well exceeds 330 volts. How often is your AC voltage increasing that much?
Duke Energy demonstrates how 'dirty' a UPS voltage can be in figures 1 and 2. Clean AC mains voltage is not left. What the UPS outputs when switched to battery in on right. That UPS voltage is dirtier. Potentially harmful to some motorized appliances. And perfectly ideal for all electronics:
http://www.duke-energy.com/indiana-business/products/power-quality/tech-tip-03.asp
If voltage variations are harmful, then one said what internal part is at risk. Few do. Most only recite hearsay from advertising rather than learn facts.
Apparently that dimming is trivial since the electrician did not hunt for and fix that defect. Unfortunately, some ignore more serious dimming since it has been seen too often by electricians who foolishly use back stab connections rather than firmly attach a wire to each receptacles screws.
Something completely different and unrelated to low voltage (dimming lights) is a surge. Neither a power strip protector nor UPS nor power conditioner claim to protect from typically destructive surges. Some only claim to protect from a completely different surge that is made irrelevant by protection already inside the Mac. Your concern is a rare anomaly that can overwhelm superior protection inside the Mac. That completely different anomaly must be averted by something completely different - a properly earthed 'whole house' protector. Another completely different anomaly that is really only about $1 per protected appliance, easily installed, and mostly unknown to most who also fear dimming.
