Advanced calculations for energy consumption, efficiency analysis, inverter selection, carbon footprint assessment and Conversions like Energy, Power, Frequency, Time, Carbon Emissions and Efficiency Conversion.
No loads added yet. Add loads to see calculations.
Enter your energy consumption to calculate environmental impact.
Efficiency is output over input, but stating it as a percentage hides the engineering consequence. The useful question is how much power is being turned into heat, because that is what sets the thermal design.
| Efficiency | Loss in a 1 kW converter | Relative to 95% |
|---|---|---|
| 99% | 10 W | 0.2× |
| 95% | 53 W | 1.0× |
| 90% | 111 W | 2.1× |
| 80% | 250 W | 4.7× |
Moving from 90% to 95% sounds like a five-point gain but halves the heat to remove — often the difference between a fanless design and one needing forced cooling. Below about 90% the loss figure grows very quickly, which is why high-power equipment is designed to efficiency targets rather than described by them.
A converter quoted at 95% achieves that at one particular operating point, typically somewhere between half and full load. At light load, fixed overheads — controller quiescent current, gate-drive charge, core loss — stay roughly constant while the output shrinks, so efficiency collapses. At very high load, conduction losses that rise with the square of current take over.
This is why a supply sized generously for a small load can be less efficient in practice than a smaller one properly matched, and why standards such as 80 PLUS specify efficiency at several load points rather than one.
Efficiencies of cascaded stages multiply rather than average. Three stages at 90% give 0.93 = 72.9%, not 90%. Each conversion step added to a power chain costs real energy, which is the argument for reducing the number of conversions rather than optimising each one in isolation.
Divide output power by input power and multiply by 100. The loss is the difference between them, and that figure is usually more informative for design purposes.
Because loss is what must be dissipated as heat. Going from 90% to 95% in a 1 kW converter cuts loss from 111 W to 53 W, which can remove the need for a fan entirely.
Because fixed overheads such as controller quiescent current, gate-drive charge and core loss stay roughly constant while output falls. Efficiency therefore drops sharply at low load even in a well-designed supply.
They multiply. Three stages at 90% each give 0.9³ = 72.9% overall, which is why reducing the number of conversion stages often helps more than improving any single one.
Often less, in practice. Running well below its optimum load point puts it in the region where fixed losses dominate, so a correctly sized supply usually performs better.
A certification that specifies minimum efficiency at several load points rather than one, precisely because efficiency varies across the load range and a single headline number can be misleading.