When those in charge of the local transport system in Santa Cruz, California, wanted to replace some of its ageing diesel and CNG (compressed natural gas) buses, their initial thoughts were to go green with battery-electric buses.

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But when the Santa Cruz Metropolitan Transport District (Santa Cruz Metro) test-drove one of the “best electric buses money could buy for our needs” — weighing it down with sandbags to replicate the weight of its full passenger capacity — it had problems navigating the steep hills outside the coastal city.

“We couldn’t get the bus to get over the hill at 50 mph, and once it got there, it didn’t have enough charge to get back,” regional transport commissioner and Santa Cruz Metro director Mike Rotkin told local online news outlet Lookout Santa Cruz.

The bus then needed charging for several hours before it could return to the city — and the operator realised that battery-electric would not be able to meet its needs.

Last month, the board of Santa Cruz Metro announced it had approved the purchase of 57 hydrogen-powered buses — and will begin a procurement process for what will be “the largest acquisition of FCEBs [fuel-cell electric buses] in North American history.

It aims to have 48 single-deck buses and nine longer, articulated vehicles on the road within 18 months.

A total of $87.4m has been allocated for the purchase, but almost all of that will be provided by state and federal grants. The bus operator itself will only contribute about $900,000.

Metro CEO Michael Tree told Lookout Santa Cruz that hydrogen buses have a “fourfold advantage” over battery-electric options.

First of all, he said they have a longer range — 300-350 miles (483-563km) versus 175-200 miles; they can be fully “charged” in about 15 minutes, compared to several hours for battery buses; they are lighter and therefore less taxing on roads and bridges; and they will still work if a natural disaster cuts off the electricity to the city. Hydrogen filling pumps can be backed up by diesel generators; although the buses will not work if their hydrogen supply is cut off, as it currently is in much of southern California.

Historically, buses have been an important tool helping local people escape floods, earthquakes and wildfires, Tree explained.

In a separate interview with the Santa Cruz Sentinel newspaper, back in August, when the plan was first announced, Tree said that the total capital costs for infrastructure were lower with hydrogen than batteries, because far fewer refuelling stations were required than charge points.

Santa Cruz Metro also has funding to build a hydrogen filling station in the city, and plans to build a second in the neighbouring city of Watsonville, which is in its catchment area of Santa Cruz County.

But Rotkin acknowledged that hydrogen buses are not always the best option. Indeed, the transport agency already operates ten electric buses, and plans to convert its entire fleet to zero emission by 2037 with a mixture of battery and fuel-cell vehicles.

“Electric buses make more sense if you are on totally flat ground, but in hilly Santa Cruz County, battery electric buses do not work so well,” he told the website.

“No-one makes an electric bus that has enough power to take a fully loaded electric bus over the hill at the speed limit.”

Tree also admitted that hydrogen was not cheap, with the price in the majority of California’s 53 hydrogen filling stations recently rising to all-time high of $36/kg.

But he said that hydrogen would cost the equivalent of $9-13 per gallon for diesel. While this is much higher than the average $6.455 today, Tree points out that hydrogen will provide more than twice as much mileage as the gallon-equivalent of diesel, which will even out its higher costs.

However, as he admitted to the Santa Cruz Sentinel, the hydrogen being used will not be green — 70% will come from natural gas, with the remaining 30% coming from wind, solar and biomass, at least initially.

This could change if a $1.2bn green hydrogen hub in the state is awarded funding from the federal government under its $8bn H2Hubs programme.