Sincerely "name of a colleague"

[Joj]

Can someone help me with the email below.

Sincerely "name of a colleague",

Please find attached the quotation you requested about the PV system of the building in "name of the city";

I assumed that each apartment would have 7 panels and designed the inverter and the batteries accordingly.

However, because I haven't seen the roof in person, I can't give you an accurate estimate of the number of panels; however, I will be visiting the site tomorrow. Do you want me to inspect their roof?

 

[Skrej]

You can't use 'sincerely' as a greeting. It's used as a closing and should be followed by your own name.

You need to use something like 'Dear' followed by the person's name you are writing to. There are other more informal greetings, but 'Dear' is the standard formal greeting.

I would probably break your second-to-last sentence into two sentences and do away with semicolon. It's not wrong, but it just makes for an unnecessarily long sentence.

You write 'their' roof. Just to double check - you're writing to one person about a roof belonging to a third party, correct? If that's the case, then your final sentence is okay.

I would also add some kind of closing, such as 'sincerely', followed by your name. Multiple other options are possible. We have many more options for closings than we do for greetings.