Facts about the project

Owner: Ain K.
Planner: Kristjan K., SigmaSystems OÜ
Photovoltaic power: 7.02 kWp
Inverter: SMA Sunny Tripower 7kW
Heat storage size: 1800-liter buffer storage
Building type: Single-family home
Year of construction: 1994
my-PV product in use: 1 x AC ELWA 2
2 x AC ELWA-E
System control: my-PV WiFi Meter

What was the journey to photovoltaic heat?

The single-family home, located near the city of Vöru in South Estonia, enjoys a surprising abundance of sunlight despite the country's Nordic location. With sun hours comparable to Central Europe, the demand for photovoltaic systems in Estonia is steadily increasing. Upon installing a PV system on his rooftop, Ain K., the homeowner, quickly realized that a significant portion of the generated energy was fed into the public power grid.

In Estonia, where PV power is on the rise, feed-in tariffs are particularly low during daylight hours and the summer season, when a high yield of renewable energy production is fed into the grid.

Naturally, Ain K. was looking for methods to enhance his self-consumption, particularly during daylight hours. Additionally, he aimed to utilize the surplus energy to heat up the heat storage, which serves both as a source for heating the house, including the bathroom floor and sauna throughout the year, and for producing domestic hot water.

Personal customer opinion and resumee

“Overall, I am satisfied that I can use the majority of the generated PV electricity within my household, resulting in reduced pellet purchase costs and less heating system maintenance. Life has become more comfortable.”, summarizes Ain K. his experience with the new system.

How did you come to my-PV?

Kristjan K., from the Estonian company SigmaSystems OÜ did the planning and installing company of the PV plant on his roof and recommended to replace the installed 3 kW electric heater with a simple on/off swtch, which was not suitable for the application with PV, with the linearly controlled AC ELWA 2 in order to fully utilize the performance of his PV system.

Were there any obstacles during the setup?

Not the installation of the AC ELWA 2, however an initial analysis revealed a critical issue: optimizing consumption in a three-phase network with only one phase proves detrimental to consumers within the Estonian electricity grid. Unlike other systems, Estonia calculates consumption separately for each phase, both in terms of kilowatt-hours (kWh) and financially. Merely utilizing one or two phases results in the need to purchase the equivalent electricity from the third phase. An option is to use the electricity produced in one phase in that phase only – leading to significant energy loss. To counter this issue, each phase is regulated by using one AC ELWA 2 as well as two AC ELWA-E devices to simultaneously and individually regulate each phase.

Good to know

This is similar to a project in Czech republic, where three single-phase AC•THOR devices were installed.

Explanation of the system

Recognizing this, the owner and the installer decided to introduce additional my-PV devices to address the issue. With two units in place, self-consumption rates surged to approximately 70%. The addition of a third AC ELWA 2 unit in April 2024 yielded impressive results: self-consumption skyrocketed to a staggering 98% between April 3rd and April 19th, 2024. This substantial increase demonstrates the remarkable effectiveness of the owner and planner’s strategy, not only in Estonia but potentially in other countries facing similar challenges.

Ain K. notes that under Estonian conditions, solar energy production significantly decreases during the winter months – the PV system goes into hibernation from November to February. However, particularly during the cool but sunny spring and autumn seasons in Estonia, when both PV production and heating demand peak, the system is most effective. During the summer months, energy demand naturally doesn't remain consistently high. The 1800-liter storage typically reaches temperatures of 75-80°C, which is more than sufficient for household needs.

Household Members – hot water demand, etc.?

This configuration with two AC ELWA-E and one AC ELWA 2 adequately fulfils the heating and hot water requirements for a family of 2-3 members from May to September.

What are the benefits, in your opinion, of the changes or expansion with photovoltaic heating?

The Estonian homeowner is very satisfied and holds lofty expectations for his newly installed system: “Overall, I expect a substantial increase in annual self-consumption, reaching between 80-85%, alongside a notable reduction in pellet consumption per year. In Austria, the compensation of three-phase consumption with a single AC•THOR 9s solar diverter is feasible. However, in Estonia, installing three units of single-phase my-PV devices is a more practical approach due to financial & measuring regulations by Estonian grid operators.

This project is future-oriented, with plans to integrate an electric car. By storing surplus PV electricity in the car's battery, any excess energy can be effectively utilized, potentially even leading to a shortage of produced electricity. Fortunately, there is ample available space on both the roof and walls for further expansion.”

AC ELWA 2 in use

Make the most of solar energy and increased self-consumption

To maximize the self-consumption of your current PV system, AC ELWA 2 harnesses the system's surplus photovoltaic energy to heat your water. Increasing self-sufficiency simultaneously safeguards against unpredictable or rising operating costs.

More infos about AC ELWA 2

Back to overview

More Reference Projects

AC ELWA 2 in an architect's house

The new solar-electric heating element in a renovated single-family home in Upper Austria.