Review the options available for the inverter. Many inverters are available with features such as corrosion resistance, overvoltage protection, overheating protection, low voltage protection, battery charging capability, 240 volt capability, voltage and amperage monitoring, and automatic load sensing. If what you need is portable power for occasional use on shop truck, these options may not be beneficial, but if your inverter is to be part of a home power or marine system they can be invaluable. The qualified technicians at SOLAR ALASKA can discuss the various styles and options with you in more detail and assist you in the selection of the best type of inverter for your needs.
Inverters are normally sized by output wattage capability. Understanding a couple of simple concepts will enable you to select the proper size for your needs. First, the inverter will normally have two ratings with respect to output capacity. The first is the wattage that it can sustain on a prolonged basis. This is normally the published rating. For most inverters it is the wattage that the inverter will support on a continuos basis, but not always, so check the specifications to verify. (The Trace 812 inverter, for instance, is rated at 800 watts but this is the wattage it will sustain for 1/2 hour. Its continuos rating is 675 watts.) The second wattage rating is that which the inverter can support on a short term basis for momentary surges in demand and is called the surge capacity. All electrical devices require more electrical current to start than to run. For some devices, such as fans or computers, this additional starting wattage is minimal. For other equipment, such as water pumps and refrigerators, the starting wattage requirements can be three times the operating wattage requirements. Check the surge capacity rating to ensure that the inverter will operate and start your electrical devices.
The second concept to consider is the conversion efficiency of the inverter. This refers to the amount of electrical loss that is incurred in converting the electricity and can be extremely important if battery power is expensive or difficult to replace. The amount of loss is influenced by the quality and type of inverter and by the percentage of the inverter capacity being utilized. All inverters have an optimal efficiency range and most good inverters will have a conversion efficiency of 95% or better in their optimal range. It is important that the inverter be sized so that it is normally operating in its optimal efficiency range. A 95% efficiency means that 5% of the power is being lost in the conversion process.
In comparing the output capability of the inverter to your electrical requirements, remember that, at 110 volts AC, one amp equals 110 watts. If you have a skilsaw that uses 7 amps to operate and 15 amps to start you will need 770 watts and 1650 watts of inverter power respectively. The qualified technicians at SOLAR ALASKA can assist you in assessing your electrical load requirements and properly sizing your inverter.