Our building's water chiller is ageing and the bills are creeping up, how do we decide repair versus replace?

You're asking the right question, because with chillers the next repair bill is only part of the picture. The decision really turns on three things: efficiency (an old chiller loses efficiency and burns noticeably more power for the same cooling, which shows up exactly as your creeping bills), reliability (rising breakdown frequency and the cost and downtime each one causes), and refrigerant (if it runs an older phased-out refrigerant, future gas and parts get scarce and expensive). If it's fundamentally sound with one isolated fault, repair it. But if you're seeing efficiency loss plus repeated failures plus an obsolete refrigerant, replacement usually pays back through lower running costs and fewer outages, and that running-cost saving is the number most people leave out of the comparison. Get a water chiller service in Dubai to assess efficiency, refrigerant type and condition and give you real repair-versus-replace numbers, don't decide on the last invoice alone. The power bill is where an old chiller really costs you.