Add info on reducing rtl_wmbus cpu usage when only listening to T1/C1.

README.md

@@ -239,6 +239,18 @@ These telegrams are expected to have the data link layer crc bytes removed alrea
 rtlwmbus, to spawn the background process: "rtl_sdr -f 868.625M -s 1600000 - 2>/dev/null | rtl_wmbus -s"
 for each attached rtlsdr dongle. This will listen to S1,T1 and C1 meters in parallel.
 
+Note that this uses a noticeable amount of CPU time by rtl_wmbus. You can therefore use a tailored rtl_wmbus
+command that is more suitable for your needs.
+
+rtlwmbus:CMD(<command line>), to specify the entire background
+process command line that is expected to produce rtlwbus compatible
+output. The command line cannot contain parentheses. Likewise for rtl433.
+
+To reduce the rtl_wmbus CPU usage you can try this command line:
+An example of a command line that only listens to T1/C1 meters (disable S1 (-p s) ) and trades
+lower cpu usage for reception performance (-a):
+`rtlwmbus:CMD(rtl_sdr -f 868.95M -s 1600000 - 2>/dev/null | rtl_wmbus -p s -a)`
+
 rtlwmbus(ppm=17), to tune your rtlsdr dongle accordingly. Use this to tune your dongle and at
 the same time listen to S1,T1 and C1.
 
@@ -250,10 +262,6 @@ rtl433(ppm=17), to tune your rtlsdr dongle accordingly.
 
 rtl433:433M, to tune to this fq instead.
 
-rtlwmbus:CMD(<command line>), to specify the entire background
-process command line that is expected to produce rtlwbus compatible
-output. The command line cannot contain parentheses. Likewise for rtl433.
-
 stdin, to read raw binary telegrams from stdin.
 These telegrams are expected to have the data link layer crc bytes removed already!