Ages ago I picked up a Sola 200 power conditioner while cleaning out an empty computer shop. This thing is heavy and has an output of 1 kVA. It makes a humming noise while in operation but that is normal for the device from reading the manufacturer's specifications.
Now is a power conditioner more useful than a UPS? Below are the specifications for this beastie.
INPUT
Voltage
220 or 240 Volt AC
Frequency
50Hz
Input Voltage Range +10%, -20% (±40%)
Protection
ANSI/IEEE C62.41
A and B waveforms suppressed to safe levels
OUTPUT
Nominal Voltage
220 or 240 Volt AC
Frequency
50Hz
Voltage Regulation
±3% for +10%, -20% input
+5%, -8% for ±40% input
Efficiency
90%
Response Time
Return to regulation envelope within 30 msec.
Dynamic Response Continuous and smooth correction for input voltage fluctuations
OVERLOADS
200% of rated load for 10 seconds without damage. 500% of rated load for 10 msec.
ELECTRICAL NOISE ATTENUATION
Transverse Mode
60dB typical (80dB max) 4kHz to 20MHz
Common Mode
120dB typical (140dB max) 2kHz to 1MHz
OUTPUT HARMONIC DISTORTION
Less than 3% THD on linear loads.
No greater than 5% on typical computer loads
OVERLOAD PROTECTION
Output short circuit protection
so it won't work as a battery backup (UPS)