Energy efficient
Uses electricity only while you run the tap
The heater has up to 98 % efficiency. When you turn off the tap, the heating stops, so you do not use electricity keeping a tank warm.
Why choose Coax
Replacing a conventional water heater can pay off, especially if the old tank loses a lot of heat. Weigh the potential savings against your needs.
A tank loses heat even while you are at work or the cabin stands empty. With a flow-through heater you avoid that loss.
See the example below and answers to questions about showers, electricity use and grid tariffs. Then use the calculator to estimate costs based on your own water use.
What a tank costs you when nobody is using it
A modern, well-insulated 200-litre hot water tank loses around 55 watts to the room, all the time. That is roughly 480 kWh a year before anyone has turned on a tap. Older tanks often lose twice as much.
At today's electricity price, that is NOK 600 to 1 200 a year just to replace heat loss. It costs more at cabins, where the electricity support scheme does not apply.
COAX uses zero watts when the tap is closed.
The saving depends on your hot water consumption, the age of the tank and the electricity price. Enter your own figures in the calculator to compare.
SourcesOSO, OSO Hotwater, opens in a new tabSSB, Statistisk sentralbyrå, opens in a new tabStrømstøtte, hvakosterstrommen.no, opens in a new tab
Work out your own consumptionWhat people ask us about
Will the shower be good enough?
That depends on the power output and the incoming water temperature. In winter the water comes in at 5 to 8 degrees, in summer around 12. An 18 kW heater gives around 7 litres per minute at 40 degrees in winter, and closer to 9 in summer. A modern shower head uses 6 to 9 litres. We always size for winter.
But it draws 18 kW. Won't that be expensive?
Power output and energy use are different. Running an 18 kW heater for a four-minute shower uses 1.2 kWh, about the same as heating that shower's water with a tank. The difference is that the tank keeps using electricity for the other 23 hours and 56 minutes.
What about the capacity tariff?
Since 2022 the grid tariff has included a capacity component set by your three highest hours in the month. A ten-minute shower is 3 kWh in that hour, not 18. If you shower at the same time as the car is charging and the oven is on, you may move up a band. We will help you find a heater that covers your needs.
SourcesElvia, Elvia, opens in a new tabRørhåndboka, Rørhåndboka, opens in a new tab
See all questions and answersCompact wall unit, 5–10 cm deep
The heater mounts on the wall and fits in tight spaces, such as a small bathroom or cabin.
Water heated as you use it
The water is not stored in a lukewarm tank where legionella can thrive. The Norwegian Institute of Public Health recommends that hot water tanks are kept at 70 degrees; COAX heats the water as it passes through the unit.
Never run out of hot water
You do not have to wait for a tank to reheat between showers.
Stainless steel heating chamber
The chamber is built in several layers and prevents limescale build-up. The heater has no anode to replace and no moving parts. Some customers still use the heater they bought in the early 2010s.
IP25 protection with full electrical isolation
The heater protects against scalding, overheating and leaks. Set the temperature with the thermostat and check the operating status on the LED display.