Power Consumption Calculator
Build a load list — get total watts, daily Wh, monthly kWh, and recommended solar size.
| Load Name | Watts | Hrs/day | Wh/day | $/mo | |
|---|---|---|---|---|---|
| 500 | $2.25 | ||||
| 3,600 | $16.20 | ||||
| 320 | $1.44 | ||||
| 390 | $1.76 | ||||
| 30 | $0.13 | ||||
| 14,000 | $63.00 | ||||
| 8,000 | $36.00 | ||||
| 2,500 | $11.25 | ||||
| Total | 12,905 W | 29,340 Wh | $132.03 |
How to Use This Calculator
Build your load list
The calculator starts with eight common home loads. Edit any row's name, watts, or hours. Click the × button to remove a load you don't have. Click + Add load to add more loads — useful for off-grid solar systems, RV builds, or custom applications that don't fit the preset appliance list.
Watts vs. Wh per day
The Watts column shows instantaneous power draw. The Wh/day column multiplies watts by hours to get the daily energy. The total Wh/day is what you need your solar + battery system to supply. The total peak watts is what your inverter must handle if all loads run simultaneously.
Solar sizing
Enter your peak sun hours to get an accurate solar system recommendation. The formula uses 86% system efficiency. At 4.5 sun hours (US average), a 10,000 Wh/day load requires about 2.6 kW of solar. Use the actual peak sun hours for your location — this single number can change your system size by 50%.
The Formula
The peak load figure is important for inverter sizing — your inverter must handle the maximum wattage of all loads that could run at the same time. In practice, not all loads run simultaneously; use 60-75% of peak load as a more realistic inverter sizing target for most installations.
Example
Off-grid cabin — Montana, 5 peak sun hours
Tom and Lisa's weekend cabin has basic loads: lighting, a small fridge, a laptop, phone, and a water pump.
Result
A modest 600W solar system with two 300W panels covers this cabin's daily needs at 5 peak sun hours. Two days of battery backup (50% DoD lead-acid, or one 100Ah lithium for similar capacity) handles cloudy weekends. Total system cost: approximately $1,200-1,800 DIY.