The problem
We’re adding a pool and spa to one of our short-term rentals with fully automated pumps and heaters. Which got me thinking about our older property with a dumb pump and heater and how I might be to automate them and save money on electricity operating of them.
My local electric provider offers an optional “time-of-use” rate, which works like happy-hour pricing: electricity costs more at busy times of day and less the rest of the time. I wasn’t sure whether switching would save money or cost more. My first ideas were solar, batteries, or going off-grid. Instead I connected Claude to my Hospitable account and had it test the question against my actual bookings.
Time-of-use in 30 seconds
- Standard rate: one price for every hour of the day.
- Time-of-use rate: weekday “peak” hours cost about 14¢ per kWh more than the standard price, and every other hour costs about 6¢ less.
- Weekends and holidays: cheap all day.
| Season | Expensive hours (weekdays only) |
|---|---|
| Summer | noon to 9 PM |
| Winter | 6 to 10 AM and 6 to 10 PM |
For example, running a 4 kW pool heater for one hour in peak costs about 84¢ more than running it at night off peak. Move that hour out of peak every day and it adds up. The catch is that if more than about 30% of your electricity is used during those expensive hours, the switch loses money.
How we built the plan
Claude pulled my reservation history through the Hospitable connection. Occupancy for the pool house was about 50% overall, and it swings by season. Our high and low seasons each run about six months:
| Season | Occupancy |
|---|---|
| High season (mid-Dec to mid-May) | about 73% |
| Low season (mid-May to mid-Dec) | about 40% |
| Best months (Jan to Mar) | about 77% to 93% |
| Slowest month (Sep) | about 20% |
I sent screenshots of my provider’s hourly usage for about two dozen days, some with guests and some vacant. Claude checked how much of each day’s usage landed in the expensive hours. My main house uses 35–55% of its power then, so it stays on the standard rate. The pool house uses less, so it comes out ahead.
What we found (estimates, not results yet)
- Switching rates: about $390 a year saved on the pool house, with a realistic range of $0 to $600.
- Timing the heater: running the pool heater and pump outside the expensive hours could bring the total savings to about $670 a year.
- Batteries and solar: a home battery would take about 17 years to pay for itself, and off-grid solar for the pool doesn’t pay. Grid-tied solar looks like 10–12 years.
- Heater schedule: in winter, the heater runs 10:15 AM to 5:45 PM, between the morning and evening peaks. In summer, it runs 6:15 to 11:45 AM.
Dollar figures are before taxes and fees, which make my bills about 24% higher.
How the agent keeps it up to date
A weekly task runs Monday mornings. It re-checks my Hospitable bookings through April 2027 and looks for gaps of 3 or more days between a checkout and the next check-in. For each gap it puts two 8:00 AM reminders on my Google Calendar, one to turn the heater off on checkout day and one to turn it back on before the next guest. The titles look like “Turn OFF pool heater (checkout; next check-in Nov 20).” If a new booking lands inside a gap, the next sync fixes the reminders.
What’s next
- Rate change: I’ve submitted the time-of-use request. The meter swap takes about 3 months.
- 30-day check: On Dec 9 we compare daily usage with last year, adjusted for booked nights.
- Possible automation: I plan to automate even more with a “Home Assistant Green” reading the Hospitable calendar feed and changing the heater’s temperature setting (90°F with guests, 75°F when empty) without touching a button.
Happy to share the method if anyone wants to try something similar. This is my own analysis, not financial advice, and your utility’s rules may differ.