Photo by Adheesha Paranagama on Unsplash

The Most Cost-Effective Way to Heat Your Pool in San Jose, CA

If you’re lucky enough to have a pool in sunny San Jose, California, you probably want to maximize your swim time without running up a massive utility bill. Heating your pool efficiently comes down to combining three things: smart scheduling, leveraging solar energy, and using your existing equipment wisely.

The Strategy: Solar + Auto Cover + Targeted Gas Heating

Your pool holds 15,600 gallons and currently has a gas heater, an auto cover, and a variable speed Jandy pump. Your goal is to heat the pool from 67°F to a comfortable 82°F for weekend use, without spending a fortune.

Gas heat is fast but expensive. Solar heat is free but slow. The best approach? Use your gas heater to quickly “kickstart” the temperature, then let the sun and your cover maintain it.

Heating Cost Breakdown

To raise the pool temperature 15°F using only your gas heater:

• Requires approx. 23.4 therms of natural gas
• At $2.88178 per therm, that’s $67.42

Instead, we’ll blend that cost across a few days for efficiency.

3-Day Solar-Only Heating Schedule

Even without using gas, you can make significant temperature gains with solar heat and an auto cover. Here’s a revised plan:

Total Solar-Only Temp Gain: ~6.5°F in 3 days
Estimated Total Cost (electricity only @ $0.30/kWh): ~$2.70

This gets you close to your target in a few sunny days. For quicker results, you could still do a 1-day gas kickstart, but this plan works well on a budget.

Visual Heating Curve (Solar + Cover)

Day      | Temperature Progression
---------|------------------------
Start    | 67°F
Day 1 PM | ~68.5°F
Day 2 PM | ~70°F
Day 3 PM | ~71.5°F

• Solar Gain: ~2.5°F/day with pump circulation and sun exposure
• Night Loss: ~1°F with auto cover closed
• Net Daily Gain: ~1.5°F

Visualizing this on a line chart, you’d see a steady upward climb from 67°F to 71.5°F over 3 days, with shallow dips overnight.

Maintenance Mode: Keep It Warm for Free

After reaching your target temperature:

• Run pump at 1000 RPM for 4–6 hours during the day
• Keep auto cover closed at night
• Expect 2–3°F solar gain during sunny days, with only ~1°F loss overnight

This lets you swim comfortably all weekend long, with minimal added cost.

Pro Tips

• Always heat and circulate during sunny hours (10 AM – 2 PM)
• Avoid running the heater overnight
• Use the auto cover consistently
• Consider adding a solar cover beneath your auto cover for even better retention

By mixing smart scheduling with your existing setup, you can have a warm, inviting pool without a high gas bill.

Automation Setup Suggestions (Jandy System)

1. Create 3 Custom Schedules
   • “Weekday Heating”: Disabled (to save energy)
   • “Weekend Prep (Solar Only)”:
     • Friday 10 AM–4 PM: Pump @1600 RPM
     • Saturday 10 AM–4 PM: Pump @1600 RPM
     • Sunday 10 AM–4 PM: Pump @1600 RPM
   • “Maintenance Mode”: Daily Pump @1000 RPM, 11 AM–5 PM
2. Enable Auto Cover Reminders
   • Use app or smart home alerts to remind you to close the cover at night
3. Optional: Add a solar controller and temperature sensor for further automation

With this schedule and automation, you’ll enjoy a warm pool every weekend while keeping energy costs in check. Happy swimming!