Shorthand for 1.7kW or 1,700 Watts. The shorthand is common in some fields, I've mostly seen it in electronics where you might have 4k7 to represent 4.7 kOhm or 4,700 Ohms.
This is a new one to this old dog. 2k18 is 2018. 1k7 looks to me like 1007. Much shorter to use 1.7kW which most know how to parse to 1.7 x 10<sup>3</sup> Watts.
I can vouch for the fact that 1k7=1700 is a common convention. It comes from the face that . can be hard to read sometimes. You often also see something like an “0R5” resistor which is 500 milliohms.
You, but in the case where the shorthand is required, the suffix (W in this case) is also dropped, or at least has been every time I've seen or used it.
It's a fairly common notation on printed circuit board resistors where a dot could get lost. Better readability. They usually drop the suffix though, not sure if it's common for non-resistance items to use, but I got what he was trying to say.