Solar pool heating, measured — not promised.
Every number on this page is a live reading from the pool and spa at our own installation. Two nearby pools with no solar heating are logged right alongside them — one sitting in full sun, one in shade — so every comparison here is a direct measurement, not a model or a projection. Continuous logging of this system and its controls started June 12, 2026, and runs 24/7. The full raw record is open to anyone.
Browse the record
Solid days are loaded · dashed days are older history — tap one to fetch it from the logger.
Our pool, open data
This is our own pool, and the record is fully open. Take the raw data and run your own analysis — or come by and experience the water in person. Either way, you don’t have to take our word for it.
⬇ Download the full dataset Every raw sensor reading behind this page, live from the logger, as a CSV spreadsheet (several MB — best on Wi-Fi).Two nearby pools with no heating at all. Ours sits in shade most of the day, so the shaded reading is the baseline every boost figure on this page is measured against — the stricter of the two. Our pool is dotted here for scale.
Daily Summary
The season so far
Measured Jun 12 – Jul 29, 2026 · 44 days of data
How these numbers are measured
Our pool. Everything on this page comes from the pool and spa at our own working installation. Sensors log a reading about once a minute, around the clock, to a public data log — and this page reads that log directly, so what you see is the raw record.
The controls. Two extra sensors sit in unheated water beside the pool — one in full sun, one in shade. They show what water does with no heating at all. Every “boost” figure is simply the pool or spa temperature minus the shaded reading at the same moment: a direct measurement, not a model or a projection.
Why we measure against the shaded control. Our pool sits in shade for most of the day, so shaded water is what this pool would actually be doing without the solar system — that’s the honest thing to compare it against. The full-sun control is still logged — it has its own chart under “Dig deeper” — but it describes a sunnier pool than ours. Note which way this cuts: unheated water in full sun warms itself more than unheated water in shade, so measuring against the shaded control makes the boost figures larger than they would be against the full-sun one. Both readings are in the downloadable data if you want to run the comparison the other way.
Our heating limits. These are the limits we set on our own system, not a ceiling on what solar can do: the controller stops heating once our pool nears — °F or our spa nears — °F. Peak temperatures are capped on purpose — on hot, sunny days the water would climb past those lines without them.
The gas heater. The system also has a gas heater. A gas burn warms water far faster than sunshine can, which makes it easy to spot in the data. Days the heater runs are flagged automatically, and its rise is never counted in any solar statistic.
Data gaps. If a sensor goes quiet for more than an hour, the gap is shaded on the chart instead of being smoothed over.
Definitions. “Swim hours” are noon to 10 PM. A day counts as swim-ready when the pool averages — °F or warmer during swim hours.
Cost comparison. Each day’s measured temperature rise — minus a conservative allowance for the natural warming unheated water gets anyway — is converted to BTUs and priced at what a gas heater would burn to deliver the same heat, shown as a range from natural gas to delivered propane. On days the gas heater ran, only the solar preheat before it fired is credited, never the heater’s own rise.