Intel has been working with the industry to develop and distribute software and firmware mitigations for Spectre and Meltdown. The company says that although they don't have information that these exploits have been used to obtain customer data, they now have additional data on the impact on some client platforms.
Testing on several 6th, 7th and 8th Generation Intel Core processor platforms using Windows 10 reveals modest performance drops.
The performance impact on 8th generation platforms (Kaby Lake, Coffee Lake) with SSDs is small. Across a variety of workloads, including office productivity and media creation as represented in the SYSMark2014SE benchmark, the expected impact is less than 6%.
7th Gen Kaby Lake-H performance mobile platform are similar to the 8th generation platforms but 6th generation Skylake-S platform, are hit a little harder.
Intel has published their data so you can take a look at what impact you can expect on your systems.