Just had a look at this site http://www.aquasonic.com.au/?page=home
and it has 3000watt heaters. Your usual 300 watt heater does about 300litres of water so would I be right in assuming as a rough guide 3000 watts would do up to 3000litres?
and it has 3000watt heaters. Your usual 300 watt heater does about 300litres of water so would I be right in assuming as a rough guide 3000 watts would do up to 3000litres?