Configure your computer to go into sleep mode when you haven’t used it for 10-15 minutes. Also, while most people think that screensavers save power, they do not. A screensaver is not as energy-saving as putting the computer to sleep.
Get rid of your outdated tank-style water heater and substitute it with a modern tankless model. These still use fuel and electrical energy to make water hot, yet they only heat what you use rather than continuously charging the entire container. You can purchase tankless heating systems in styles that can give just one faucet or whole property direct access to water that is hot.