investment ( 25 %) would be approximately 16 years , for vehicles that have historically been kept in service for more than forty years . During this service life , battery replacements may be necessary , with current technology estimated to require replacement once every ten years , adding another factor to our decision .
Looking forward however , we do project maintenance costs on the current PTVs to increase substantially with a 15-year forecast of $ 3.4 million per year . In addition , as battery costs continue to decline , it is possible that our current cost estimates for the new electric PTVs are overly conservative . For example , if we can acquire new PTVs at a cost of $ 1.5 million per vehicle , which is still roughly 65 % more than the cost of an electric bus in today ’ s market , our total investment including charging infrastructure would be approximately $ 74 million . With fuel savings of $ 550,000 per year and maintenance savings of $ 1.7 million for a total of $ 2.25 million , after a ZEV grant of 75 %, the payback on our investment ( 25 %) would be approximately 8 years . As we continue to gather more information from manufacturers , we will fine tune our analysis . In addition , we will maintain our dialogue with the FAA and approach other potential funders to assist in this initiative .
Best Practices Opportunities Electrification of Bus Fleets
Another important pillar of our fuel reduction and air quality improvement goals is to evaluate our options for electrifying the Authority ’ s bus fleets over time . Like the PTVs , diesel and compressed natural gas ( CNG ) buses emit harmful landside emissions and are expensive to operate and maintain . As noted earlier , our bus fleet across both airports totals 47 vehicles , with 26 diesel buses in operation at Dulles International and another 21 buses at Reagan National , of which 15 are diesel and 6 are CNG . 13 This fleet of buses completes more than 500,000 annual individual trips to and from garages , terminals , parking lots , and rental car centers each year , accumulating more than 2 million miles in the process . This translates into more than 480,000 gallons of diesel fuel use per year at a cost of approximately $ 970,000 and an additional 34,000 gallons equivalent of CNG at a cost of $ 45,000 . In addition to fuel costs , in 2019 , we spent approximately $ 380,000 maintaining the 21 buses at Reagan National and just over $ 1 million dollars maintaining the 26 buses at Dulles International .
Prior to the current slowdown in air travel , we had previously included funding for new EV buses in our 2020 budget . With current economic conditions and reduction in near term demand , the existing bus fleet ’ s life cycle can be extended , and procurements are planned for later years . As with the PTVs , we will continue to seek financial assistance from the FAA and others ( i . e ., Volkswagen ) to reduce the financial impact to the Authority . In addition , as electric buses become more mainstream , vendor financing and novel battery lease structures may also be options .
Emissions Benefit from Electrifying a Diesel Bus
As a bus approaches the end of its useful life ( i . e ., 15 years ), it is typically replaced to maintain our level of service to airport customers and employees . Traditionally , we have replaced a diesel bus with a current-technology diesel bus or with a CNG bus . Moving forward , however , our efforts will be more focused on replacing an existing diesel or CNG bus with an EV bus with the priority being replacements of diesel buses at Dulles International given their condition .
13 We acquired our CNG buses for Reagan National in 2007 . At that time , buying EV buses was not an option .
Today , we are not considering any additional CNG purchases given the EV options available and the expected cost declines going forward .
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