It is fairly certain that electricity storage will grow. Especially short-term storage, i.e., solutions providing synthetic inertia, which Merus has to offer. Already, there are large motors idling in Ostrobothnia and Estonia because natural inertia is insufficient. Solar power and wind power connected via converters do not produce any inertia at all. Hydropower produces relatively little inertia, although it works well as medium-speed balancing power and particularly as long-term storage.
In this multi-month timescale storage, hydropower is in a class of its own, but it has also been largely tapped out. Cross-border transmission connections allow Finnish wind power to be stored in the reservoirs of neighboring countries. They likely have nothing against buying nearly free electricity and saving their reservoir water for more expensive times. The market mechanism works quite successfully as a driver for production, demand response, and storage.
This doesn’t significantly affect Merus per se, but I would predict that the construction of electric boilers will decrease somewhat in the future. A builder of an electric boiler must be able to assume that electricity will be nearly free on average during the summer. Finland has Europe’s largest electric boiler and the world’s largest electrically heated sand battery.
Electrical energy storage generates profit from price volatility, but the economics of district heating water and other industrial-scale electric heating depend on the absolute price. (At the ESE power plant, the boiler is not used when the spot price of electricity rises above four cents per kilowatt-hour.) Cheap electricity attracts, among other things, data centers and the transmission connections, storage, and other price-balancing measures built for their needs. Industrial-scale electric heaters will not disappear, of course, but their construction pace will likely slow down at some point.