High Wattage and High Initial Current
Air Conditioners and Water Heaters are high wattage appliances. When a compressor of an air conditioner is running it needs high current. Below are some representative wattage based on air conditioner size:
Max kVA (assuming 0.85 power factor)
1300 Watts or 1.3 kW
1900 Watts or 1.9 kW
2500 Watts or 2.5 kW
The wattage here is instantaneous power demand or the electricity required when all the components of air conditioner are running. But it varies during the running of an air conditioner because the compressor switches off when the temperature of the room reaches the level set in the thermostat. During the time the compressor is switched off, the electricity consumption is only for a few components in the air conditioner, which is much less. Also the initial starting current is high.
Similarly for electric water heaters the wattage requirement is 2-4 kW or 2000-4000 Watts. The high wattage is required only till the water is heated to a certain temperature.
To handle high loads of air conditioners or water heaters the inverters connected to a solar power generation system should be able to handle high load. So one needs about a 3 to 5 kVA inverter system to handle the same. Most commonly used home inverters are low kVA inverters that cannot handle this load. Also one would also want other appliances in a house to be running and not just the air conditioner, so this increases the overall size of the system.