As people grow older, their walking efficiency declines, posing constraints on mobility and affecting independence and overall life quality. While wearable assistive technologies are recognized as a potential solution for age-related movement challenges, few have proven effective for older adults, predominantly within controlled laboratory experiments. Here we present WalkON, a pair of soft robotic shorts designed to enhance walking efficiency for older individuals by assisting hip flexion. To assess the impact of WalkON in daily walking activities, we initially conducted a technology assessment with young adults on a demanding outdoor uphill 500m hiking trail. Subsequently, we validated our findings with a group of older adults walking on a flat outdoor 400m track. WalkON significantly reduced the metabolic cost of transport by 17% for young adults during uphill walking. Concurrently, participants reported high perceived control over their voluntary movements (self-reported mean score of 5.67 out of 7 on a Likert scale). Similarly, older adults experienced a 9% reduction in metabolic cost when using WalkON during level ground walking, while retaining a strong sense of movement control (mean score of 5.85 out of 7). These findings emphasize the potential of wearable robotic assistive devices to enhance energy efficiency in daily outdoor walking, suggesting promising implications for promoting physical well-being and advancing mobility, particularly during the later stages of life.