For specifiers and installers, helping an off-grid user select a low NOx energy efficient water heater is critical — and a condensing continuous flow water heater using LPG is one of the most efficient and environmentally friendly options available. By choosing a continuous flow water heater instead of a standard electric water heater, an end user can reduce energy costs by up to 50% and reduce greenhouse gas emissions by up to 61%. When compared with oil-fired systems this saving is even greater.
Tests show that a Rinnai Infinity condensing water heater emits 35.18mg/kwh NOx compared with a typical oil boiler that emits approximately 364 mg/kwh NOx. That means a Rinnai condensing water heater emits approximately 10% of the NOx that an oil boiler emits, a 90% reduction. Therefore, combining a gas boiler and a Rinnai water heater will radically reduce NOx.
On the 26th September 2018, the EU introduced new stricter parameters for NOx emissions in the gas water heater category. The new NOx level was set at 56mg/kwh. Rinnai water heaters are well in advance of the criteria demonstrating product quality and superior performance.
The new criteria for oil fired boilers or liquid fuels has been set at 120mg/kwh, highlighting that current appliances and the oil-fired market has some way to go before it can achieve a similar level to that of gas.
If we compare the production of CO₂ between gas and electricity we find that for every GJ (277.78kW) of energy used gas will produce 44.44kg compared to 103kg with electric. We can see that for the same energy used electricity will produce twice the amount of one of the major greenhouse gases.
The efficiency of this type of electrical generation is as low as 40%. So, if we now compare the use of electricity to LPG to heat hot water we find that electricity is 40% efficient in comparison to a Rinnai water heater which returns 107% nett efficiency.
Electricity is not the ‘green’ fuel that its marketing portrays it to be. It produces more CO₂ than LPG but is also less efficient, by far.
An LPG continuous flow water heater is an ‘on-demand’ system. When a hot-water tap is opened, the unit reads the demand and starts the heating process. The water flows through a heat exchanger, where it heats to the desired temperature using only as much gas as is needed. When the tap is turned off, the heater automatically shuts off.