When I started reading this thread, I thought the topic was appliances as in: range, refrigerator, microwave or range hood, and dishwasher. It would seem that a monthly budget number for each unit would vary by property as some have additional amenities -- like a washer and dryer. First one would need to understand how the appliance package is defined -- as in "what kinds of appliances would be included".
Later posts mentioned heating and air conditioning equipment. Obviously the first cost of this equipment would probably be the highest cost "appliances" on a property (if they were defined as appliances.) But, the recurring property cost for this kind of equipment can be controlled with three simple steps:
1. When new equipment is installed, file the warranty paperwork. Out of the box equipment comes with a five year warranty. Most manufacturers will extend the parts warranty to ten years if the warranty registration is completed. Look for additional warranty considerations. One HVAC manufacturer and MRO supplier offers a special two-year warranty that replaces the outdoor unit if the compressor fails or the coil leaks during the first two years of use. (These are normally the most difficult repairs.) To make the program even better, the manufacturer provides a $300 per unit allowance for use by the property which helps with labor cost to install the replacement or money for putting a resident in a hotel for the night if the unit is out of service and the temperatures outside are extreme.
2. Install the unit correctly -- including having the correct amount of refrigerant in the system. This can be confirmed by using a set of refrigerant gauges. If the onsite maintenance team is not qualified to install the equipment, there will be extra cost in having an outside contractor handle that. But, consider the additional cost an investment as properly installed and set up equipment will result in fewer equipment failures (and unhappy residents) in the future.
3. Adhere to a preventive maintenance program. The useful life of equipment can be extended if filters and coils are kept clean. In cooling, air flow through and around the unit is necessary to provide the transfer of heat from areas where it isn't needed to areas where it doesn't matter. The air flow is also necessary to keep the unit from being over worked while trying to maintain the comfort level and temperature requested by the resident.
And, when we've done those things -- we won't be any closer to providing a monthly budget number, but we will at least have made an effort to get that number under control!