If he uses an inverter an even higher demand on the battery/alternator is required than using straight DC motor, because there is an efficiency loss of at least 10 to 20% with an inverter. So 40 amps DC for 1/2hp DC motor direct goes up to approx 100amps DC to supply the invertor for a 1hp AC motor. Not something I would do but hey, whatever.
Inverter losses and AC motor efficiency have less losses than DCI2R losses and DC motor efficiency. Plus no tinkering with the compressor is required. Plus the inverter can be used to operate essential loads during power outages such as sump pumps and furnaces .
Understanding 12V inverter efficiency
Inverters do not achieve 100% energy conversion during operation and the efficiency of an inverter is usually measured as the ratio of output power to input power. For example, a 12V inverter with an input power of 1000W and an output power of 870W has an efficiency of 870W/1000W = 87%.
In general, the efficiency of an inverter can be between 85% and 95%, depending on the quality of the inverter design, the working load, and the amount of output power. An efficient 12V inverter optimizes the use of energy and ensures that energy is wasted as little as possible when supplying power to devices. This not only saves energy but also reduces the environmental impact of energy consumption. By using a high-efficiency inverter, you can use electricity in a more environmentally friendly way and reduce your energy costs.
Factors affecting inverter efficiency:
Quality of design
The quality of an inverter's design and topology has a direct impact on its efficiency. High-quality inverters tend to have higher efficiencies because they use superior electronics and advanced circuit designs. In addition, inverters improve energy efficiency by using pulse width modulation (PWM) techniques and high-frequency switching, effectively minimizing energy waste.
Load
The efficiency of an inverter is usually highest within a certain load range. Both low and high loads result in lower efficiency. When inverters are designed, a certain load range is usually taken into account to achieve optimum efficiency. In practice, it is possible to ensure that each inverter operates within its optimum operating range by distributing loads appropriately, thus increasing efficiency!
Operating temperature
Inverters can lose efficiency in high-temperature environments because high temperatures affect the performance of electronic components. Inverters are usually designed with heat dissipation and temperature control measures to maintain a low operating temperature.
Waveform types
Different types of inverters (e.g. square wave, modified wave, and pure sine wave inverters) have different efficiencies. In general, pure sine wave inverters have higher efficiencies because they require more complex circuitry to produce outputs that are close to a sine wave.
Is 120V more efficient than 12V?
In general, a given inverter may be more efficient at converting 12V DC to 120V AC. This is because at higher output voltages, less current is required to transfer the same amount of power, and therefore less resistive losses are incurred.
Assuming that 100 watts of power need to be converted from DC to AC if the input voltage is 12 volts and the output voltage is 120 volts, this corresponds to an input current of 100 watts/12 volts ≈ 8.33 amps and an output current of 100 watts/120 volts ≈ 0.83 amps. In this case, the output current is lower, the resistive losses are lower, and the inverter may be more efficient.
However, factors such as inverter design, load profile, and operating temperature must also be taken into account to determine which voltage level is more efficient. Different inverters can perform differently in terms of efficiency at different voltage levels. Therefore, when selecting an inverter, it is also necessary to take into account the actual application needs, design requirements, and other factors that affect efficiency.