ELWA in use

Hot water with the sun in Germany

The sun sends no bill: Thanks to ELWA, the sun provides hot water at no cost, even in the German Harz region.

Facts about the project

Photovoltaic power and orientation
Heat storage size (boiler or buffer storage)
Building type
Year of construction and number of square meters:
my-PV product in use
my-PV Referenzprojekt ELWA Harz PV-Module

An owner of a brick-clad old building in the Lower Saxony city of Goslar heats his hot water with the sun – and that in the rainy Harz region in Central Germany. With the ELWA by my-PV no grid connection, and thus no bureaucratic procedures, are necessary to harness the power of the sun. As the ELWA directly utilizes direct current (DC), it operates off the grid and is self-sufficient.

An escape from rising gas prices

Faced with the surge in gas prices in 2022, Mr. Zogbaum, like many of our customers, sought an alternative for his gas condensing boiler. The lack of supply security coupled with unpredictable political decisions, impeded the continuation of the existing technology. For over a decade, Mr. Zogbaum had relied on a gas condensing boiler with the belief that it was the optimal heating system.

Personal customer opinion and resumee

"my-PV offers other great solutions for large PV systems – but for me, cost-effectiveness and a rapid implementation were decisive. Hence, I chose the ELWA. I installed it in June, and by October, the gas heating remained turned off. With the power of the sun and the linearly controlled system, we ensured the constant supply of hot water. There hasn't been a single day where the water temperature dropped below 37°C in the 200-liter hot water tank," summarizes Mr. Zogbaum based on his experiences with the ELWA.

“What has always bothered me was the fact that in summer, I had to remain the heating switched on solely for hot water. My gas consumption in the summer was about 150 kWh per month, purely for hot water,” calculates Mr. Zogbaum, highlighting the use of gas in the summer for hot water preparation, which is economically not meaningful.

Why not a heat pump?

At that point, the resident of Goslar began his search for alternatives. After thorough research, he alternated between a hot water pump and the solution involving a PV heating element from my-PV. After careful consideration, the customer opted for the heating element. This decision was motivated by several factors: The hot water heat pump also requires electricity, and to achieve the same result, the customer would have had to make a larger financial investment. The PV heating element, my-PV's ELWA, requires no additional electricity, as the power is supplied exclusively from the photovoltaic system, thus heating water solely with solar energy. Not least because of its easy retrofitting and low financial expenditure, the maximum benefit has been achieved.

Were there any obstacles in the implementation?

Given that the customer ordered my-PV’s ELWA precisely during peak demand, the most significant challenge during planning was the extended delivery times. At that time, it took almost a year for the PV heating element to be delivered to the Harz region.

As of October 2023, due to tremendous efforts and expanded production capacities, ELWA is once again fully deliverable and available from stock.

What is the household's hot water demand?

"We are a two-person household and do not consume 200 litres of hot water. The 200 litres in the hot water storage tank are entirely sufficient for us. Throughout the operational period so far, we had adequate hot water available, even on days with low sunlight, thanks to the yields from the previous day,” analyses Mr. Zogbaum.

Are there any further expansion plans or considerations?

Since the linearly controlled PV heating element can handle more power than what is currently installed on the roof, the hot water supply result is remarkable. "In hindsight, I would go for two more modules. But it works very well with four modules too," affirms the resident of Goslar.

Individual needs and usage can vary from user to user. He does not want to feed PV electricity into the grid and, therefore, does not want a grid connection, as it wouldn't align any longer with ELWA’s suitability for hot water production. In that case, he would have to switch to a grid-connected product from my-PV.

my-PV Referenzprojekt ELWA
my-PV Referenzprojekt ELWA
my-PV Referenzprojekt ELWA
my-PV Referenzprojekt ELWA
my-PV Referenzprojekt ELWA
my-PV Referenzprojekt ELWA
ELWA Seitenansicht


in use

ELWA is a 2 kW photovoltaic water heating device. Direct current from photovoltaic modules is transferred directly to the built-in heating element and immediately converted into heat without loss.

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