Let’s Encrypt is a certificate issuing authority that issues SSL Certificates absolutely free of cost. There are no hidden expenses. It provides DV certification, meaning it only verifies that you own the domain. It issues certificates for a single website and all its sub-domains and uses SHA-1 with 2048-bit RSA for encryption. The certificate provided is valid for 90 days, however they will automatically regenerate a new certificate every 60 days.
The easiest tool to create and install SSL certificates for Windows is LetsEncrypt-Win-Simple. First, you need to download the latest version (zip file) from here and extract it to the directory on your Windows server. AfterSSL Certificates Lets Encrypt
Lets Encrypt has set a 90 day certificate lifetime intentionally. They feel a certificate with a shorter lifetime is more secure, as it limits the damage from key compromise and mis-issuance. And if stolen, the keys andSSL Certificates Lets Encrypt