>> You keep using that word; I do not think it means what you think it means. -- [[https://www.youtube.com/watch?v=G2y8Sx4B2Sk|Inigo Montoya in the Princess Bride]] ====== "Efficient" ====== The word //efficienct// is often mis-used in vanworld to mean something like: * //better// * //preferable// * //makes more power// * or, perhaps more cynically, //the thing I bought// ... without describing the use case. It will simplify matters if we think of efficiency as ''power in / power out''. Round numbers example: if a component requires 220W in to make 200W out then it is ~90% efficient with ~10% lost, typically as heat. Made up examples: * 200w inverter, 85% efficient * 1000w inverter, 80% efficient Which one can make more 120v power? The 1000w one. Which one is more //efficient//? The 200w one. ===== getting it wrong ===== ==== solar panels ==== [[electrical:solar:panels#efficiency|Solar panel efficiency]] doesn't mean //how much power the panel will make// or anything like that. A more efficient panel and a less efficient panel **of the same rated wattage** will harvest the same power, all other things being equal. Panel efficiency is a mathematical relationship between the panel's **area** and its rated power. **Efficiency makes no difference** unless you are maxxed out for panel space. ==== solar charge controllers ==== MPPT are not more //efficient// than PWM controllers. MPPT have DC-DC conversion losses (typically ~5%) and PWM do not. Will the MPPT harvest more in Bulk? Yes, on average MPPT controllers will harvest ~13% more energy (Watt-hours) from sunlight than the same system on PWM. But it incurs losses while doing so. There are [[electrical:solar:charge_controller#when_pwm_beats_mppt|scenarios where PWM can harvest more power than MPPT]] because of MPPT's buck/boost losses. ===== getting it right ===== [[electrical:inverter|Inverters]] are the usual case where efficiency is discussed accurately; see the examples at top. Even then we often do not account for standby losses.