MicroFIT 2.0 defines the 'nameplate capacity' as the larger of inverter size or array size. in other words, both your inverter and your PV array must be less than or equal to 10kW (=10,000W). Unfortunately, and strangely, this decision seems to have been made without the benefit of PV design experience.
Most contractors and system designers will be trying to hit exactly 10kW of array size (for systems unconstrained by roof area). This looks good on paper, but may result in poor system performance over the system's lifetime.
Common PV module sizing includes 250W modules, so 40 x 250W = 10kW quite nicely. Arrays with 40 modules (regardless of module size) will be designed in 4 strings of 10 modules. However, for most grid-tied inverters strings of 10 will result in poor hot weather performance, a problem that will get worse as the modules age. Such a system could spend a significant portion of each hot day not producing at all, as the array cannot sufficiently drive the inverter. (Just think of this past July: hot and sunny.)
Strings of 11, 12, or 13 are a much better design and that's what we use in our designs. So a system based on 44 x 225W modules = 9.9kW is a more robust design than 40 x 250W = 10kW. Similarly, 39 x 250W = 9.75kW is more robust than 40 x 250W, even though it's 250W smaller. In fact, strings of 13 represent the best design, maximizing system efficiency and prolonging inverter life.
String sizing issues can be eliminated all together by using micro-inverters. Whether or not micro-inverters are worth their premium price will depend on your site details.
Overall preferred system design will be based on your site. Call us to set up a site assessment and we can recommend a system design for you!