Current consumer friendly rack battery LFP prices are at around 400 EUR/kWh for 6000 cycles at 80% degrations, that's 0.074 EUR per kWh out the the battery. 5

Current consumer friendly rack battery LFP prices are at around 400 EUR/kWh for 6000 cycles at 80% degrations, that's 0.074 EUR per kWh out the the battery. 5 kW inverter price are about 700 EUR, if you assume you have to change them every 7 years and you're getting 6 MWh/year out of the inverter that's 0.017 EUR/kWh. PV prices are around 0.5 EUR/Watt peak and where I live in France you get about 1000 hours of equivalent peak production per year so that's 0.02 EUR / kWh produced by the panels assuming 25 year life. All in all you're at about 0.11-0.12 EUR/kWh if you manage to consume all produced/stored kWh, which is easy if you have one or two electric vehicule charging at home. As mentionned here the hard part are 3-4 winter month where solar production is way lower than the rest of the year. An additional data point for gaz form of energy storage: a standard "35kg" propane bottle has about 450 kWh of energy in it, if you need 1.4 MWh of heat in the winter to complete solar + heat pump output that's just three bottles. To my knowledge no way to produce/fill it from gaz produced from summer electricity with home sized equipment (yet).