Daily Energy Budget

The Daily Energy Budget is a soft constraint – a kWh/day guide that helps pace your energy use. It does not override the hourly capacity system. Instead, it produces a daily soft limit for the current hour, and the planner uses the smaller of that and the hourly capacity soft limit.

Key distinction: Unlike the hourly capacity limit (hard cap), the daily budget will never trigger emergency alarms or "shortfall" flows. If PELS cannot shed enough devices to meet the daily budget, it simply continues operating without panic. Only projected breaches of the hourly hard-cap budget trigger emergency intervention.

This feature always uses the whole-home meter data that PELS already collects (the same stats used for hourly and daily usage).

Budget-Exempt Devices

Budget exemption is a control rule, not a meter rewrite:

• Exempt devices are ignored by daily budget soft-limit control.
• Their real usage still counts in used, remaining, deviation, and budget overrun reporting.
• They are treated as uncontrolled load when PELS builds and learns the daily budget plan.
• They still count toward hourly capacity protection, including hard-cap and margin shedding.

This means a budget-exempt device can leave the household over the daily budget without causing other devices to be shed just to compensate for that exempt load.

Terminology

Shared capacity terminology and units are defined in:

• Getting Started: Terminology and Units

Daily-budget-specific terms:

• Daily soft limit: A soft limit derived from the daily plan (history + price shaping). Never triggers panic/shortfall.
• Effective soft limit: The smaller of the hourly soft limit and daily soft limit – this is what the planner uses for shedding decisions.
• Allowed by now: Planned cumulative kWh at the current local-hour bucket.
• Remaining: daily_budget_kWh - used_today_kWh (kWh, can be negative).

What It Does

• Builds a plan for how much energy should be used across the current local day.
• Tracks how much energy has been used since local midnight.
• Computes how much is "allowed by now" based on the plan.
• Computes a daily soft limit for the current hour from the plan.
• Freezes the plan for the rest of the day if the budget is overspent. If the day is underspent, the plan can still rebalance.
• Uses the smaller of the hourly soft limit and the daily soft limit (effective soft limit).

How the Soft Limit is Applied

PELS always computes the hourly soft limit for the current hour. When daily budget is enabled, it also computes a daily soft limit for the same hour. The planner then uses the smaller of those two (the effective soft limit) when deciding shedding and restores.

The daily soft limit is capped at the hourly hard cap (before margin). This ensures the daily budget never allows more power than your grid connection supports.

Important: End-of-hour capping (which prevents bursting at the end of an hour) only applies to the hourly soft limit, not the daily soft limit. Daily budget violations are not time-critical in the same way – there's no penalty for exceeding a daily budget at 11:55.

Examples (Scenarios)

1) Over plan, daily soft limit becomes the limiter

It's 15:00. The plan says you should have used 35 kWh by now, but you have used 40 kWh. The daily soft limit for this hour becomes lower than the hourly soft limit. The planner uses the effective soft limit (the smaller of the two), which reduces headroom. As a result, some restores won't happen and low-priority devices can be shed earlier.

2) Behind plan, hourly soft limit stays in charge

It's 10:00. The plan says 18 kWh by now, but you have used 12 kWh. The daily soft limit becomes higher than the hourly soft limit, so the hourly soft limit remains the limiter. Restores and boosts are still allowed if there is headroom.

3) Overspent early hour, plan freezes until you catch up

At 08:00 the plan allowed 6 kWh, but you already used 7.5 kWh. The daily budget "freezes" the plan while you are over plan. Once usage drops back under plan, it can rebalance again.

4) Price shaping enabled

You enable price shaping and prices are cheap from 01:00–05:00 and expensive in the evening. The daily plan shifts more of the remaining allowance to cheap hours, which raises the daily soft limit overnight and lowers it during expensive hours.

5) Daily budget off

Daily budget disabled means PELS uses only the hourly soft limit and price optimization (if enabled). There is no daily pacing.

Settings

The daily budget controls live in the Budget tab.

• Enable daily energy budget: turns the feature on/off.
• Daily budget (kWh): target daily energy use. Range: 20–360 kWh.
• Price-shape today plan: when price optimization is enabled, the plan is weighted toward cheaper remaining hours.
• Reset learning: clears the learned usage profile for future plans.

Advanced tab tuning (expert)

The Advanced tab includes two daily-budget tuning controls:

• Controlled usage weight (default 0.30): balances uncontrolled vs controlled influence in learned profile blending and how split caps/floors are allocated (0 = uncontrolled, 1 = controlled). Historical caps/floors are recomputed from a rolling 30-day window using robust hourly quantiles (with fallback to raw extrema when sample count is low).
• Price flex share (default 0.35): max price-shaping strength for controlled load; automatically reduced on low-spread price days.

Warning: these controls can significantly change pacing behavior, shed order timing, and restore timing. Keep defaults unless you are deliberately tuning behavior. If you change them, adjust one parameter at a time and observe at least a full day.

For exact formulas and worked examples, see Daily Budget Weighting Math (Advanced).

Today Plan View

The Budget tab shows a "Today plan" chart and live stats:

• Used: kWh used so far today (local time).
• Allowed now: cumulative kWh that the plan allows up to the current hour.
• Remaining: daily budget minus used (can be negative).
• Deviation: used minus allowed so far (positive means over plan).
• Confidence: backtested forecast-skill score — how regular the home's hourly usage is, and how well it follows shifted budget plans when controlled load exists.
• Price shaping: shows whether price shaping is active.
• Plan frozen: appears while budget-controlled load is over plan; exempt devices can leave reporting over plan without freezing the daily plan.

The chart shows planned kWh per hour as bars, with actual kWh per hour as dots for completed hours.

Buckets and DST

Buckets are computed from local midnight to the next local midnight. On DST transitions, the number of buckets can be 23 or 25, and hour labels may repeat on fall-back days.

How the Plan Works (High Level)

• Default profile: a safe baseline distribution across the day.
• Learned profile: updated at the end of each day from actual usage.
• Profile blending: ramps from default to learned over time (internal, not shown in UI).
• Price shaping (optional): reweights remaining buckets based on today's prices.

The plan is a cumulative curve. The current bucket's planned kWh is turned into a daily soft limit for that hour, and the planner uses the effective soft limit (smaller of hourly and daily).

Interaction With Other Features

• Hourly capacity limit (hard cap): Always enforced. Daily budget never bypasses it. Only projected breaches of this hourly hard-cap budget trigger emergency shortfall alarms.
• Daily soft limit: Combined with the hourly soft limit by taking the smaller limit. Never triggers emergency alarms.
• Budget-exempt devices: Skipped by daily-budget control, but still visible in real usage and still managed by hourly capacity protection.
• Price optimization: Can reshape the daily plan if price shaping is enabled.

Insights

These are exposed on the PELS Insights device:

• pels_hourly_limit_kw (effective soft limit in kW; the lower of hourly and daily soft limits)
• pels_daily_budget_remaining_kwh
• pels_daily_budget_exceeded
• pels_limit_reason (indicates whether limits are due to hourly or daily budget)