An inverter converts direct current (DC) from a battery or solar array into alternating current (AC), which powers most household appliances. Understanding a few key specifications helps explain why some systems perform reliably while others struggle.
1. Continuous Power and Surge Power
Continuous power is the output an inverter can sustain under specified operating conditions. Surge power is the higher output available briefly when equipment starts. Refrigerators, pumps, and other motor loads can require substantially more power at startup than during normal operation. Both the surge rating and its duration matter.
2. Pure Sine Wave Output
A pure sine wave inverter produces a smooth AC waveform resembling utility power. Modified sine wave models produce a stepped waveform that may cause noise, extra heating, or compatibility problems with certain devices. Appliance requirements determine which output waveform is suitable.
3. Power Is Not Energy
Inverter capacity, measured in watts or kilowatts, describes how much load it can supply. Battery capacity, measured in watt-hours or kilowatt-hours, describes stored energy. A larger inverter alone does not extend backup time.
For example, a battery providing 2,000 Wh of usable DC energy through an inverter operating at 90% efficiency could theoretically power a constant 300 W load for approximately six hours:
Runtime ≈ 2,000 × 0.90 ÷ 300 = 6 hours
Actual runtime varies with battery condition, temperature, inverter idle consumption, and changing appliance demand.
4. System Compatibility Matters
Battery voltage must match the inverter’s specified input range. The battery and its management system must also support the required discharge current. Solar input limits, charging functions, and backup capabilities differ between inverter types.
5. Heat Affects Performance
Inverters lose some energy as heat. Restricted airflow or high ambient temperatures can reduce available output or trigger shutdown. Manufacturer clearance requirements help maintain reliable operation under demanding everyday conditions.