A Texas Commission on Environmental Quality grant will cover $708,618 of the bill, and Hays CISD will be responsible for the remaining $474,382.
Interest earnings from the district's 2014 bond will pay $444,983, and the remaining $30,199 will be provided by HCISD's general fund.
Funding from the 2014 bond is permitted because buses were part of voter-approved expenditures, according to district Chief Operations Officer Max Cleaver.
The new vehicles will replace 10 diesel buses in the district's fleet, and the older models being replaced will be permanently disabled by drilling into the engine block mechanically or chemically, which Cleaver said was required by the grant.
He also said HCISD does not have existing infrastructure to fuel the buses, which will cost some $800,000 to build. An additional grant may be pursued to cover roughly 60% of the cost, and a mobile fueling service will be used as a stop-gap.
Trustees weighing the costs and benefits of the environmentally cleaner technology ultimately decided it would be worth the investment.
"We tend to be trained to think in terms of costs versus benefit, the cost benefit analysis model, but sometimes we're asked to think in terms of what's morally correct," District 3 Trustee Michael Sánchez said. "The air quality is certainly a moral question. At what point do we want to have clean air for ourselves and for our children, and for the general environment in terms of the pollution that diesel engines do produce."
Cleaver said HCISD's long term plan is to purchase a total of 30 propane-fueled buses to diversify the district's current fleet of 226 diesel buses. The propane fleet would cost an average of $58,000 per bus, once the fueling system and additional grants are factored in, and will run roughly $1.7 million all told.
Proposition A of HCISD's 2021 bond, which will be presented to voters in the May 1 election, will purchase another 28 diesel buses for $3,386,200 if approved. Comparable diesel buses cost $117,000 under the bond and do not have grant funding.
Cleaver said the propane buses have a shorter range and lifespan than diesel buses, with propane buses lasting 150,000-180,000 miles compared with the diesel's 200,000 miles, but maintenance is expected to be cheaper and more environmentally friendly.
"I have to say I'm really excited about this purchase," District 2 Trustee Willie Tenorio Jr. said. "I think it's going to be a good thing for the environment and for Hays CISD."