Most European residential electric systems operate at 240v, versus 120v in the US, which means you can only backfeed a US outlet with half the power you could in a European outlet. That alone makes this system half as useful for US applications.
Remember the tmobile un-contract? This is literally from their press release in 2017: "T-Mobile ONE customers keep their price until THEY decide to change it. T-Mobile will never change the price you pay for your T-Mobile ONE plan. When you sign up for T-Mobile ONE, only YOU have the power to change the price you pay." https://www.t-mobile.com/news/press/un-carrier-next
Remember how they promised the FTC they wouldn't raise prices if they could pretty please merge with sprint to become the biggest telecom network in the country? https://www.yahoo.com/news/t-mobile-promises-sprint-merger-195428217.html
Sorry for the industry jargon, but measuring things in kW won't give you the full picture, you want to compare things in "kWh". Your utility bill should show your price in $/kWh and the solar company should have given you a production estimate from Helioscope or some kind of similar energy estimating software that shows expected annual kWh output
Their pricing looks good, you're getting black on black modules and optimizers for a bit over $2 per watt after incentives. As someone who works in the industry I'd say that's a pretty decent price.
What have they promised for your annual production estimate? Also what's your current cost of power?