Adventures with EVs often involve big mountain climbs, which consume additional energy, impacting range. I recently had the opportunity to drive climbs from Bright to Omeo and back via Mt Hotham, in Gunaikurnai and Taungurung country, and get a sense for how EVs handle hills.
I collected efficiency data for each leg of a road trip from Melbourne, giving a baseline 4.5km/kWh efficiency on the flat, and showing significant variation with gradient of climb or descent, as below:
The “flat” baseline is the drive between Melbourne and Bright, and the big gradients are the climbs to Mt Hotham; 1350m/55km from Bright and 1000m/50km from Omeo.
Hill: climb it
This small data gives me some rules of thumb:
- A mountain climb roughly halves efficiency, to 2.7km/kWh,
- A descent gives at least 2-5x better efficiency, to 10-25+ km/kWh,
- The round trip climb and descent uses 0-25% more energy than the climb,
- The net effect of climbing and descending is negligible on a longer road trip
I’m still enjoying the novelty of EVs reclaiming gravitational potential energy on the descent, including the nerdy thrill of clocking the game to net generation, which is possible between Mt Hotham summit and Harrietville (-1180m/30km).
Planning calibration
Another rule of thumb in my initial planning was that any EV would use 5-10% of battery capacity for a 1000m climb–does this check out? I saw an extra 8kWh to climb 1000m/50km and an extra 9kWh to climb 1350m/55km, which is 7-8% of 96kWh battery capacity per 1000m. Planning calibrated.
As a sidebar, I’ve squeezed in more road trips with roof loads between this trip and the first road trip, showing the actual impact of drag is less than assumed.
| Efficiency/range compared to baseline | Assumed | Actual |
| Surfboards | 85% (roof) | 89% (roof) |
| Bikes (additionally assume more drag on roof) | 70% (rear) | 80% (roof) |
Hill climate
While I could get detailed planning information for any scenario from an app like ABRP, I want to keep developing my intuition and rules of thumb based on real-world experience, in order to plan independently, sense-check calculated plans, and make adjustments on the fly.
I experienced wind, snow on the road, and temperatures down to -4C on this trip, in some extremely wild weather, though I didn’t quantify the impact on efficiency. However, given that the weather caused power outages, and could have caused mobile network outages, or forced detours or extended stops, it reinforced the case for additional layers of resilience in planning.
It’s great to complete an EV road trip with some big hills, to get a better feel for how the EV handles these adventures, and build confidence for more.
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