This Instructable will show how to run your home HVAC less often during Time-of-Use peak hours and potentially cut power bills in half on extreme days. I implemented this using a VeraLite smart home controller and tested with both Z-Wave and Nest thermostats.
How does it work? Just imagine during peak hours repeatedly switching your thermostat to Cool for 5 minutes then to Off for 10 minutes. That s all your HVAC needs anyway on a moderate day, but on very hot days it will run less than needed to maintain the temperature you selected. You will continue to get regular bursts of cool air to give some comfort but at a fraction of the cost.
This is automated by coding a Vera scene to run every minute and switch between modes. Scenes are written in Vera s Luup (Lua-UPnP) language and can be triggered to run based on timers or events. It works for both heating and cooling and allows customization based on your power company s time-of-use plan, which may have different costs based on time of day, day of week, or month.
You will need a working knowledge of coding, create and running Vera scenes, and debugging when things go wrong. I provide basic working code examples but you must modify them for your application. To get started you ll need:
- Details of your power company s Time-of-Use plan
- Vera smart home controller, like the VeraLite ($99)
- Any Vera compatible thermostat I have specifically tested this on:
It would be straightforward to modify these concepts to SmartThings and other controllers. Feel free to copy, share, and create your own Instructable to improve upon these ideas.
We received a Nest Thermostat as a wedding present (awesome friends, right?) and it s a cool gadget but it really hasn t saved much money. Someone is home almost all the time so Auto-Away rarely kicks in, and hot California summers either keep the AC running all the time or not at all if you set it too high. With Pacific Gas & Electric with rates ranging from $0.10 to $0.50 per kWh that can be $30 a day. Ouch!
As you can see from the picture above I have been able to flatten those costs out during peak hours. In spite of the high temperature of 107F on Wednesday July 29th 2015 the daily cost was about $12.50.