Note that no coal plants have started construction since the events at Fukushima. (But perhaps you're referring to the original phase-out agreement from 2000.)
> After 2011, when Germany decided once and for all to phase out nuclear power, a total of 6.7 GW came into service while coal plants with a capacity of some 3.8 GW were retired. Since planning and construction of a coal-fired power station takes at least three years, capacity added after 2011 had been planned before the accident in Fukushima, Japan – the event that led to Germany’s final nuclear phase-out policy.
> As of 2017, no new lignite-powered stations are planned, according to the Federal Network Agency (Bundesnetzagentur). The possibly last new hard coal unit ever built in Germany is envisaged to come online in 2018: Uniper’s Datteln 4, with a capacity of 1,055 MW, after years of legal struggle with local environmental organisations.