On Wed, 2 Dec 2020 14:04:59 -0800 (PST), Thomas
wrote:

Bought a sous vide 800 watt cooker. Can I safely use in a 2 slot outlet?
15 amp service, older house, maybe from 1965 or so.


No .
... a 3-prong plug will not insert into a 2-prong receptacle.
... always glad to help.

ps: if your 1965 house has 2-prong receptacles
and a 15 amp service - it's not a house.
John T.