Hospitals require large quantities of very clean air ventilation 24/7. It takes a lot of fan energy to push the required amount of air through the necessary quality of air filters. As air filters capture more and more dirt, it requires more and more energy for a fan to maintain the required air flow. Generally speaking, one can purchase cheap air filters that will not hold much dirt. The first cost of the filters is low while the frequency of filter replacement and fan energy consumption are high. It costs more to purchase a set of air filters that hold more dirt but they last longer and require less fan energy.
Unfortunately, most hospitals were designed when energy efficiency was not very important. The typical air filters were not nearly as cost effective as some of the modern filters. In order to minimize the Total Costs of Ownership (TCO) for air filters, we must replace the old style filters with modern filters AND tell our designers to specify the most cost effective filters in new equipment.
Positive Cash Flow within 6 Months
Is this worth the effort? It is not unusual to save $150/bed @$0.11/KWH by using the most cost effective air filters. Using the lowest TCO air filters can be so beneficial that is can be cost effective to throw out the old filters rather than use them up. Some vendors will take the old filters back.
Many air filter vendors will provide a free audit of the prevailing filters used and compare the purchase cost, labor costs and energy costs to potentially better (lower TCO) filters that can replace the existing. Sometimes the existing mounting structures must be modified.
Facility staff can audit their own filters, get manufacturers data for those filters along with more appropriate filters and plug the numbers into the air filter comparison tool.
A third approach would be to have an air filter expert not affiliated with a manufacturer do the work. This might produce the best results because one manufacturer may not produce all of the most cost effective products. A 270 bed hospital was able to save about $35,000 per year by investing $3,000 in expert assistance.
If Fans are Fixed Speed, Energy Consumption Will Increase with Better Air Filters
Energy savings account for most of the value of air filter upgrade. If the supply fans have variable speed drives, the savings calculations are legitimate. If inlet vanes are used for fan capacity control, the energy savings will be less but the retrofit will still be cost effective.