# Solar heat collectors: Correlation

Prices it moves with, and why

Source page: https://www.materialinsights.org/energy/e_solar_heat/correlation/

Solar heat collectors on roofs and in industry warm water and air directly. Their cost depends on copper, aluminium, glass and installation, and their value on the electricity, gas or LPG they displace.
 No public price Solar heat collectors has no public monthly price series: Sold as equipment at retail; no public price index.

#### What its price moves with

 Commodity [Cu Copper](https://www.materialinsights.org/commodities/copper/)Capture cost

Absorber plates and pipes in many flat-plate collectors are copper, chosen for heat transfer. Copper prices push makers to switch to aluminium or plastic. Copper remains common in higher-grade collectors.
 Not enough overlapping price history to measure.

 Commodity [Al Aluminium](https://www.materialinsights.org/commodities/aluminum/)Capture cost

Collector frames and some absorbers use aluminium. Aluminium is lighter and often cheaper than copper, so the price gap shapes designs. Evacuated tube collectors use more glass and less metal, so they are less exposed.
 Not enough overlapping price history to measure.

 Energy [Gas Natural gas](https://www.materialinsights.org/energy/natural_gas/)Rival source

Solar water heaters compete with gas and LPG heaters. High fuel prices raise the savings from solar heat. In India, solar water heaters compete mostly with electric geysers, so power tariffs matter as much as gas or LPG prices.
 Not enough overlapping price history to measure.

 Energy [HP Heat pumps, air conditioning and refrigeration](https://www.materialinsights.org/energy/e_heat_pumps/)Rival

Heat pump water heaters compete with solar collectors, and rooftop PV can run them. Cheap PV and heat pumps have slowed solar thermal growth in many countries. Both suit hot water use.
 Not enough overlapping price history to measure.

 Chemical [MEG Monoethylene glycol](https://www.materialinsights.org/chemicals/meg/)Heat-transfer fluid

Closed solar loops use glycol mixtures to prevent freezing, made from ethylene or propylene glycol. Glycol is a small cost but needed in cold climates. In warm regions plain water is used instead.
 Not enough overlapping price history to measure.

How to read these numbers

**Correlation of monthly changes** (the number in the coloured pill) compares how much each price moved, month by month, since 2006 or the first month both series exist. It runs from −1 to +1: near +1 the two usually rise and fall in the same months, near 0 there is no link, and a negative number means they tend to move in opposite directions. Above 0.7 is strong, 0.4 to 0.7 moderate, 0.2 to 0.4 weak.

**12-month changes** compare year-on-year moves, which shows whether two prices share the same cycles even when the month-to-month noise differs.

**Price function** is a straight-line fit of the two prices on logarithmic scales: price ≈ k × (partner price)^β. β is how much this price moves, in per cent, for a 1% move in the partner over the whole period, and R² is the share of the variation the fit explains. Two prices that both drift up with inflation can fit well without any real link, so read it together with the monthly correlation.

**Lead or lag** checks whether the monthly correlation is clearly higher when one price is shifted by 1 to 6 months.

Correlation is not cause. The reasons on each card explain the economic link; the numbers show how strongly it has shown up in prices. Proxy series are US producer price indexes or related prices and can blur the real link.

Data: World Bank Commodity Price Data (Pink Sheet), October 2026; US Bureau of Labor Statistics producer price indexes, IMF primary commodity prices and US EIA prices via FRED, Federal Reserve Bank of St. Louis, retrieved November 2026. Calculations by this site.

## Other sections

- [Summary](https://www.materialinsights.org/energy/e_solar_heat/index.md)
- [Overview](https://www.materialinsights.org/energy/e_solar_heat/overview/index.md)
- [Efficiency](https://www.materialinsights.org/energy/e_solar_heat/efficiency/index.md)
- [Techniques](https://www.materialinsights.org/energy/e_solar_heat/techniques/index.md)
- [Resources and labour](https://www.materialinsights.org/energy/e_solar_heat/resources/index.md)
- [Impact on the biosphere](https://www.materialinsights.org/energy/e_solar_heat/biosphere/index.md)
- [Relationships](https://www.materialinsights.org/energy/e_solar_heat/links/index.md)