So for a kilowatt and 300K with a poor quality radiator (0.8)

Area = 1000/(0.8*5.670373x10^-8*30^4)

=1000/367.4401704

≈2.72m^2

So using the approximation of 1kW/m^2 of solar, you need on the order of 2.7x the area of solar for radiators

That doesn't seem too bad, and is on par with what the ISS has. The radiators on ISS have emissivity about 0.91

Ed. With the same quality of radiator on the ISS it's about 2.4*solar kilowatts