Solar planning
Solar Load Calculator
Estimate daily appliance energy from watts, quantity, schedules and editable duty-cycle assumptions. Compare all listed loads with loads you mark as essential for solar and battery planning.
Quick estimate
Build your solar load profile
Presets are editable planning estimates. Add Custom Appliance when you know a different load.
Row details
Duty cycle is a planning estimate for how often the appliance draws its listed watts. It remains editable.
Row details
Duty cycle is a planning estimate for how often the appliance draws its listed watts. It remains editable.
Row details
Duty cycle is a planning estimate for how often the appliance draws its listed watts. It remains editable.
Row details
Duty cycle is a planning estimate for how often the appliance draws its listed watts. It remains editable.
How to calculate a solar load
For each appliance, daily energy is watts × quantity × hours per day × duty cycle. The calculator keeps energy use separate from listed running watts so a schedule does not change an appliance's nameplate load.
Duty-cycle estimates
A cycling appliance such as a refrigerator may not draw its listed watts continuously. Duty-cycle values are editable planning estimates, not universal appliance specifications, and remain visible when below 100%.
Weekly schedules and average daily load
Energy Profile schedules with fewer than seven operating days per week are averaged across seven days. That average supports daily-energy planning; it is not a worst-case daily load. If some days use substantially more energy, use conservative daily values when sizing storage.
Essential loads
Essential status is a planning choice. Imported profile rows start as not marked essential until you review them; starter rows include editable demo assumptions. Changing the Essential toggle changes the comparison, not total daily energy.
Listed-load running watts and limitations
Listed-load running watts sum the running or nameplate watts for the listed appliances if they operate together. This is not a measured peak and does not include startup surge. The calculator does not verify inverter sizing, battery or BMS current limits, circuit loading, wiring or installation compatibility.
Solar System Load Profiles & Inverter Sizing Guide
Typical daily watt-hour energy consumption profiles and continuous inverter power requirements for off-grid and backup solar applications:
| Application Type | Key Appliances Included | Daily Energy (Wh/day) | Continuous Inverter Size |
|---|---|---|---|
| Overland / RV Setup | 12V Fridge, LED lights, fan, phone/camera charging | ~600 – 1,000 Wh / day | 1,000 W – 1,500 W |
| Off-Grid Tiny House / Cabin | Energy-star fridge, Starlink, TV, laptops, lighting | ~2,500 – 4,500 Wh / day | 2,000 W – 3,000 W |
| Critical Home Backup | Fridge, deep freezer, well pump, router, security | ~5,000 – 8,000 Wh / day | 4,000 W – 6,000 W |
| Whole-Home Off-Grid | All appliances, mini-split heat pump, induction cooktop | ~15,000 – 25,000 Wh / day | 8,000 W – 12,000 W |
Daily Solar Load & Energy Demand Formulas
Calculates cumulative daily energy requirement (Wh/day) and connected peak power demand (Watts) across all AC and DC household appliances.
Daily_Wh = ∑ (Watts_i × Quantity_i × Hours_i × (Days_i / 7) × Duty_Cycle_i) | Peak_Watts = ∑ (Watts_i × Quantity_i)Variable Definitions
Watts_iAppliance Running Wattage(W)- Nominal electrical power consumed by device i.
Quantity_iUnit Count(count)- Number of identical active appliances.
Hours_iOperating Duration(hours/day)- Active operating hours per run day.
Duty_Cycle_iCycling Factor(fraction)- Percentage of active runtime drawing power (e.g., 35% for refrigerators, 100% for lighting).
Peak_WattsTotal Connected Power(W)- Simultaneous running wattage sum determining inverter size.
Engineering Notes & Standards
- Daily energy (Wh/day) determines solar array and battery storage capacity.
- Peak connected load (Watts) determines required AC inverter continuous power and breaker ratings.
Frequently Asked Questions (FAQ)
How do you calculate daily solar load in Watt-Hours (Wh/day)?
Why is refrigerator daily energy much lower than its rated wattage multiplied by 24 hours?
What is the difference between daily energy (Wh) and peak connected load (Watts)?
How do I decide which loads are essential for solar backup?
Related planning tools
Review appliance usage with the Electricity Usage Calculator. Compare solar production with the Solar Panel Output Calculator when its location and system inputs are available.