When God speaks of a new covenant, it means he has made the first one obsolete. It is now out of date and ready to be put aside. (Heb 8:13) The old system in the law of Moses was only a shadow of the things to come, not the reality of the good things Christ has done for us. (Heb 10:1)
Hebrews 3 and 4 tell us that Jesus is greater than Moses and that now, in Christ, we can enter the rest that the Sabbath pointed to. The burden of the Mosaic legal code with all its regulations about Sabbath keeping has gone. So we don't have to worry about our appliances keeping the Sabbath!