If they're crediting you for that energy at anything close to the retail electricity rate you're effectively getting a really generous subsidy. Because solar is so cheap but only produces electricity sometimes and at pretty much the same time everywhere in the region, the actual cost of electricity when your solar panels are producing heavily and feeding back into the grid is much, much lower than when they're not producing and you're a net consumer of grid power. Not only that, but it's a subsidy that's likely paid to wealthy people who can afford to install solar by poorer people who can't.