If those circumstances occur, what would you be serving that can't afford to go offline for a couple days?
It's important to have an answer to that question, rather than to assume that being offline when your home internet is down is inherently a problem. You can safely estimate using "X nines will cost X digits per month":
1 nines, 36.5 days/year downtime is $#/month. (openwifi tier)
2 nines, 3.65 days/year downtime is $##/month. (residential tier)
4 nines, 1 hour/year downtime, is $####/month. (datacenter tier)
5 nines, 5 minutes/year downtime, is $#####/month. (carrier tier)
Speaking from experience, it's both important to decide which 'nines' you require before you invest in making things more resilient — and it's important to be able to say things to yourself like, for example, "I don't care if it's down 4 days per year, so I won't spend more than $##/month on hosting it".
It's important to have an answer to that question, rather than to assume that being offline when your home internet is down is inherently a problem. You can safely estimate using "X nines will cost X digits per month":
1 nines, 36.5 days/year downtime is $#/month. (openwifi tier)
2 nines, 3.65 days/year downtime is $##/month. (residential tier)
3 nines, 9 hours/year downtime; are $###/month. (commercial tier, datacenter tier)
4 nines, 1 hour/year downtime, is $####/month. (datacenter tier)
5 nines, 5 minutes/year downtime, is $#####/month. (carrier tier)
Speaking from experience, it's both important to decide which 'nines' you require before you invest in making things more resilient — and it's important to be able to say things to yourself like, for example, "I don't care if it's down 4 days per year, so I won't spend more than $##/month on hosting it".