# Carnot batteries: Correlation Prices it moves with, and why Source page: https://www.materialinsights.org/energy/e_carnot/correlation/ Carnot batteries store electricity as heat, using heat pumps or heaters to charge a thermal store, then run a heat engine to generate power. Costs depend on cheap storage media, turbines, heat pumps and round-trip efficiency. No public price Carnot batteries has no public monthly price series: Pilot plants only; no market price exists. #### What its price moves with Energy [HP Heat pumps, air conditioning and refrigeration](https://www.materialinsights.org/energy/e_heat_pumps/)Charging Heat pump designs move heat into the store far more efficiently than resistance heaters. Heat pump cost and performance therefore set much of the round-trip efficiency and the cost of each design. Not enough overlapping price history to measure. Energy [ST Steam turbines and thermal power plants](https://www.materialinsights.org/energy/e_steam_turbines/)Discharge Many designs drive steam turbines from the stored heat, and some plan to reuse turbines and grid links at retiring coal plants. Reusing existing equipment could lower costs substantially compared with new build. Not enough overlapping price history to measure. Energy [SHS Sensible heat storage](https://www.materialinsights.org/energy/e_sensible_heat/)Heat store Most Carnot batteries store heat in molten salt, rock or concrete, the same materials as other heat stores. Cheap storage material is their main advantage over batteries for long durations. No public price for sensible heat storage, so the link is explained in words only. Commodity [K Potash](https://www.materialinsights.org/commodities/potash/)Molten salt Molten salt stores use potassium nitrate, which relies on potash. Fertiliser markets therefore affect the cost of filling the large salt tanks these plants need, although salt is a one-off cost that lasts decades. Not enough overlapping price history to measure. Chemical [HFC Fluorochemicals and refrigerants](https://www.materialinsights.org/chemicals/fluoro_intermediates/)Refrigerants Heat pumps and some heat engines use fluorinated refrigerants as working fluids, though rules are shifting designs towards natural refrigerants. Refrigerant availability and regulation therefore affect equipment choices and costs. Not enough overlapping price history to measure. Energy [LFP Lithium iron phosphate batteries](https://www.materialinsights.org/energy/e_li_lfp/)Competitor Batteries are more efficient for daily cycling, so Carnot batteries aim at long durations and at selling heat as well as power. Falling battery prices therefore narrow their potential market. 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_carnot/index.md) - [Overview](https://www.materialinsights.org/energy/e_carnot/overview/index.md) - [Science and technology](https://www.materialinsights.org/energy/e_carnot/sg-sci/index.md) - [Engineering and performance](https://www.materialinsights.org/energy/e_carnot/sg-eng/index.md) - [Economics](https://www.materialinsights.org/energy/e_carnot/sg-econ/index.md) - [Impact and additionality](https://www.materialinsights.org/energy/e_carnot/sg-impact/index.md) - [What to track](https://www.materialinsights.org/energy/e_carnot/tracking/index.md) - [Relationships](https://www.materialinsights.org/energy/e_carnot/links/index.md)