On 04-Mar-2018, ÖkoFEN with their self-sufficient house concept, had 14 days without a single kWh from the grid, generating 100% of heat and electricity from renewables.
As they state “No other way to do this all year round in cold climates”. As an example, in Austria (home of ÖkoFEN) pellets costs around 4.5 €-Cent per kWh. But since the ÖkoFEN system is a condensing boiler with 15% more efficiency this makes up for the extra fuel for Microgen’s Stirling Engine generator, so you would not need more pellets than with a standard pellet boiler.
ÖkoFEN system can generate 16 kW thermal and 1 kW electric using Microgen’s Free-Piston Stirling Engine.
