Understanding the result
Watt-hours first, amp-hours second
Watt-hours (Wh) are the most useful unit for energy planning. A 50 W appliance running for 4 hours uses about 200 Wh. Add all appliances before converting the total to amp-hours, because Ah depends on system voltage. The same energy represents different Ah values in 12 V and 24 V systems.
The calculator multiplies power, runtime and quantity, then allows for losses in wiring, inverters and electronics. The result does not recommend a particular product. It helps identify the largest loads and opportunities to preserve a reserve.
A fridge does not always draw full power all day
A fridge compressor cycles on and off. Runtime depends on temperature, ventilation, settings, door opening and the quantity of warm food placed inside. A 45 W label does not automatically mean 45 W for 24 hours. A full-day measurement in conditions similar to the planned trip is the best starting point.
Without measurements, choose cautious assumptions and compare several scenarios. Runtime may increase on a hot day. The calculator helps compare possibilities rather than hiding uncertainty behind one apparently precise number.
230 V appliances need a separate power check
A kettle, hairdryer or coffee machine may run briefly but draw considerable power. A Wh budget estimates energy, not whether the inverter and BMS can safely supply the current. Check continuous output, starting surges, BMS current, cable size, protection and operating temperatures separately.
Do not select a fuse or cable solely from these results. High-current systems need a design appropriate to cable length, installation method and equipment manufacturers' instructions.
What are equivalent sun hours?
This is not the time between sunrise and sunset. One equivalent sun hour represents an hour at the panel's full rated output. Cloud, season, latitude, shade, temperature, angle and controller losses reduce yield. Compare optimistic and cautious scenarios.
A 400 W panel does not guarantee 400 W all day. The calculator divides daily energy needs by equivalent sun hours and includes losses. If the result needs more roof space than available, consider lowering consumption, charging while driving or another energy source.
How to improve your estimates
- Measure consumption over a full day rather than a few minutes.
- Create separate profiles for summer and colder months.
- Include equipment running in the background.
- Check whether charger labels show maximum or typical power.
- Allow for poor weather and an unplanned extra day parked.
- After the first trip, compare the estimate with BMS or battery-monitor history.
Our tests go beyond specifications
Our channel shows measurements of LiFePO4 batteries, power stations, chargers and panels. Compare manufacturer claims with energy actually delivered under load and the conditions of each test.