We want to meet the demand of DHW for a single family house. To do this, you have to choose which system to use. A comparative economic study is made between a 130 L electric water heater and the Ecoheat EH130 heat pump with an accumulation tank of the same volume.
How are the new electricity tariffs?
The first point that should be kept in mind is the new electricity tariff that has come into effect on June 1, 2021. Tariff with time discrimination is the main change that has been introduced for all consumers. This means that the cost of energy will be different throughout the day. Three different time periods have been established for energy consumption: peak, mid-peak and off-peak hours; so that consuming energy at peak hours will have a higher cost than in the others. Off-peak hours are the cheapest (night and weekend period).
It is known that 3.78 kWh of energy is necessary for generation of DHW at 55 ºC. Electric water heater consumes all the necessary energy in electricity. However, electricity consumption is reduced to 1.17 kWh with the use of a Ecoheat EH130 thanks to a COP of 3.24 under these conditions. The rest of the energy is obtained from the heat contained in the outside air.
Knowing these values and the price of a kWh, the monthly consumption cost is € 28.67 in peak period with electric water heater. In mid-period, the cost is € 14.35, and € 8.43 in off-peak period. This is assuming that the system always works within the period indicated.
Heat pump to generate domestic hot water
On the other hand, the cost is reduced considerably with the use of the heat pump, being € 8.85 the monthly cost in peak period, € 4.43 in mid-period, and € 2.6 in off-peak period. In this way, the long-term savings are considerable if we install this system. For example, when both systems work in peak periods, the monthly savings reach almost € 20.
If we make an annual balance, the economic savings are quite important, being € 238 in peak period, € 119 in mid period, and € 70 in off-peak period.
In addition, the Ecoheat heat pump has another point in favour with respect to the electric water heater. And the fact is that, thanks to the smart controller that the heat pump incorporates, it allows us to make a time scheduling of the equipment so that the consumption is carried out within the off-peak period most of the time. In this way, both energy and economic savings would be even greater.