Energy Reserve: See Your Body's Battery Levels in Real-Time

What is Sonar’s Energy Reserve?

Sonar’s Energy Reserve helps you understand how much usable energy your body has in the tank. Updated continuously throughout the day, Energy Reserve combines data from all of your connected wearables, apps, and other devices to show whether you’re charged and ready to take on strain, or running low and need to prioritise recovery.

Think of it as your personal energy meter. A high Energy Reserve means your body is primed to perform. A lower score signals it’s time to recharge, rest, and avoid overextending yourself.

Unlike Sonar's Recovery Score, which offers a snapshot of your readiness each morning, Energy Reserve adjusts in real time, giving you a continuous view of your energy reserves as they respond to sleep, stress, strain, and more.

Understanding Your Energy Reserve Score

Energy Reserve is shown on a scale from 0 to 100, with higher values reflecting greater energy reserves. Your score can be broadly categorised into one of three simple zones:

• High (51–100) – You’re well-charged. Great time for focused work, demanding activity, or training.

• Moderate (26–50) – Some energy available, but stay mindful of stress and workload as the day progresses.

• Low (0–25) – Energy is limited. Prioritise rest, recovery, and sleep.

As with your Recovery, Strain, and Sleep scores, the trend over time is more informative than any signle point-in-time measurement. If your body's battery is consistently low in the morning or throughout the day, it’s a cue to adjust your approach to recovery.

How is Energy Reserve Calculated?

Energy Reserve fuses multiple physiological signals such as heart rate, heart rate variability (HRV), sleep, stress, and activity strain into one real-time view of your energy. Key contributors include:

• Heart Rate Variability (HRV): High HRV signals a relaxed, recovered state, which allows your battery to recharge. Low HRV reflects stress or fatigue.

• Heart Rate (HR): When elevated above your resting baseline, energy tends to decline more rapidly.

• Resting Heart Rate (RHR): Chronically elevated RHR can indicate poor recovery, stress, or illness — all of which impair recharge.

• Sleep Quality: Deep, uninterrupted sleep is the most effective way to fill your tank.

• Strain and Stress: Physical and mental effort both drain your battery. The more you take on, the faster your reserves decline.

Energy Reserve pulls together the most important signals from your Recovery, Strain, Sleep, and Stress scores into one real-time view — giving you a complete, moment-to-moment snapshot of how your body is trending overall. It’s a unified signal that reflects how well you've recharged, how much you’ve exerted, and what that means for your readiness right now.

What Charges Your Energy Reserve?

Your body can’t replenish energy without recovery — and that doesn’t just mean sleep. Several daily inputs help recharge your body's battery:

• High-Quality Sleep – The single most effective way to restore your battery. Deep, uninterrupted sleep allows your nervous system to fully recover.

• Passive Recharge – Periods of minimal stimulation where HR lowers and HRV rises can promote recovery even while awake.

• Intentional Relaxation – Breathwork, meditation, or short naps can trigger a shift into recovery mode.

• Lifestyle Habits – Hydration, balanced nutrition, limiting alcohol, and smart caffeine use all support overnight recharge.

You don’t need perfect stillness to recover, but calm, restorative moments help your body refuel effectively.

What Drains It?

Exertion is essential for growth — but it comes at a cost. Energy Reserve helps you keep energy expenditure in check. Common drains include:

• High-Intensity Workouts: Long runs, weightlifting, or intense training deplete your reserves quickly.

• Mental Strain: Meetings, emotional stress, and cognitive overload can be just as draining as physical activity.

• Sleep Deprivation: Poor sleep limits your ability to recharge and often leaves you starting the day at a deficit.

• Alcohol or Late Nights: Both disrupt sleep architecture and impair recovery, even if total sleep time looks normal.

• Illness or Overtraining: Suppressed HRV and elevated resting HR can prevent recharging even while at rest.

If your Energy Reserve stays low across multiple days, zoom out and look for patterns in your sleep, stress, and strain. These hidden forces can quietly erode your ability to recover, and Energy Reserve gives you the visibility to catch them before they build into burnout.

How Energy Reserve Connects to Recovery, Strain, Sleep, and Stress

Energy Reserve doesn’t replace your other Sonar scores — it connects them. It draws from the same physiological inputs that power Recovery, Strain, Sleep, and Stress to give you a unified view of how your body is responding in real time. Instead of checking four separate signals, you get one clear number that helps you act with confidence — whether that means pushing harder, slowing down, or simply staying the course.

• Recovery: Your morning Recovery Score reflects how well you bounced back overnight. It influences the starting point for your Energy Reserve each day.

• Strain: As you accumulate strain from training or movement, your body's battery ticks downward. On high-battery days, you can typically handle more strain.

• Stress: Mental or emotional stress accelerates drain. You’ll often see your battery drop more quickly during periods of Elevated or High Stress.

• Sleep: A strong sleep score contributes to overnight recharge. A good night’s rest often leads to waking up with an Energy Reserve in the 80–100 range.

How to Use Energy Reserve Day to Day

Energy Reserve is a powerful real-time signal, but the goal isn’t to stay at 100. It’s to pace your energy wisely, recover when needed, and align your effort with your capacity. Ways to use it include:

• Plan Around It: High score? Great time to train or focus. Lower score? Prioritise recovery or reduce load.

• Watch the Trendline: Rapid drops early in the day suggest a demanding workload. Schedule recovery windows accordingly.

• Time Workouts Strategically: Align harder efforts with high battery levels for better performance and faster recovery.

• Protect Your Evenings: Wind down to support overnight recharge, especially on high-strain days.

Think of Energy Reserve as your pacing partner. It won’t replace motivation or discipline, but it helps you spend energy more intentionally.

Frequently Asked Questions

Is 100 the goal every morning?

Not necessarily. Many healthy users won't see a perfect 100 every day when waking up. Consistency and trend matter much more than the daily peak.

Can Energy Reserve rise during the day?

Yes. A short nap, mindfulness session, or even quiet downtime can help your nervous system shift into recovery mode, often triggering a modest recharge.

Why is my battery low even though I slept okay?

Cumulative stress, lingering strain, or alcohol can all reduce sleep quality — even if your sleep duration seems fine.

Does nutrition directly impact Energy Reserve?

Not directly, but habits like hydration, balanced meals, and caffeine timing influence the recovery systems Energy Reserve reflects.

What if my wearable has gaps in data?

Sonar’s algorithm handles short gaps without issue. But extended time without input (like taking your wearable off for several hours) may pause updates or reduce accuracy until tracking resumes.

Balancing Data with Self-Awareness

Sonar’s Energy Reserve distills complex physiology into one clear, intuitive number — helping you stay in sync with your energy in real time. The goal isn’t perfection; it’s awareness. Use the score to spot opportunities for recovery, recognise what drains you, and understand what helps you recharge. Trust how you feel — and let the data sharpen that instinct. Over time, you’ll build a routine that respects your limits, supports your goals, and helps you feel stronger, more resilient, and more in control.