Corrections

Three so far. Each one names the pages it affected so you can see what the wrong version said and where the corrected figure now lives. The standard behind this page is that a correction gets published with the old and new numbers side by side rather than quietly edited out, and the open items list carries the ones not resolved yet.

31 August 2026: summer gas prices were inflating every verdict

What was wrong. The first build of the rate pipeline took each state's most recent monthly EIA figure. For natural gas that resolved to May or June 2026.

EIA's residential natural gas price is total revenue divided by total volume. In summer, residential volume collapses toward zero while the fixed monthly customer charge stays, so the apparent price per thousand cubic feet roughly doubles. The site was answering a heating question with summer prices.

Effect. Gas looked far more expensive than it is during heating season, which biased every verdict toward the heat pump.

A second and quieter bug sat behind the same line of code. Taking the most recent available month resolved to different months for different states, because states report on different lags. California came back as March while most others came back as May, so the states were not comparable to each other.

Fix. Both electricity and gas are now the mean of the most recent complete December to February heating season, using identical months for every state, with those months recorded in the data file and printed on every page. States without complete season data are excluded rather than estimated.

Effect of the fix. Under a cold climate heat pump against a 95% AFUE furnace, the number of states where the heat pump costs less to run fell from 19 to 4.

A second correction came out of this one. The fix above dropped any state without a complete gas season, which removed six of them from the site entirely: Florida, Louisiana, Maryland, Maine, Minnesota and New Mexico. That was the wrong rule. It is right for a gas comparison and wrong for every other comparison here, and it was worst for Maine, a state that heats overwhelmingly with oil, whose price EIA publishes, and which had four households in the dataset with no page to put them on. A missing fuel now removes a column rather than a state. All six have pages, the site went from 45 states to 51 including the District of Columbia, and the gas column on those six says not published rather than carrying a guess.

Where this now lives. The full write-up is in the note on the gas price most calculators get wrong, the fixed pipeline is described in how this site is made, and the corrected figures are on every state page and in the gas furnace comparison.

31 August 2026: the share of US homes heating with gas was wrong

What was wrong. Several pages stated that roughly 40% of American homes do not heat with natural gas. I had carried that figure from memory rather than checking it.

The correct figure. Natural gas is the main heating fuel in 47% of US homes, down from 49% in 2010, and 42% of households report electricity as their main space heating fuel. So slightly more than half of American homes do not heat with gas, not 40%.

Source. U.S. Energy Information Administration, Electricity use is becoming more common for residential heating, citing the U.S. Census Bureau American Community Survey and the Residential Energy Consumption Survey.

Effect. No calculation changed. The claim was context rather than an input, but it was stated as fact on several pages and it was wrong in the direction that understated how many households the heat pump case applies to. Corrected across the site, including the electric resistance comparison, where the size of that population is the whole reason the page exists.

31 August 2026: I called a homeowner's data impossible and I was wrong

What was wrong. I published an analysis of self-reported heat pump usage from a household in southwest Indiana: 2,160 sq ft, 499 kWh in January. Working backwards I got an implied heat loss coefficient of 1.68 BTU per square foot per degree day, called it "not possible as a whole house figure", and concluded the 2-ton unit could not be carrying the whole load.

Why it was wrong. Two reasons, and the first is mine. I used an estimated January degree day figure derived from an annual normal rather than the homeowner's actual 1,097 HDD, which alone moved my number from 1.68 to 1.82. Second, and more importantly, I reasoned from a typical house instead of reading what the owner said about theirs.

What the owner actually documented. Walls at R-21 and attic at R-83, upgraded from R-23. Ducts and air handler inside the conditioned space. A bi-level with the lower floor half below grade, which the owner estimates cuts the load on those 1,080 sq ft by around half. Simple rectangular plan, 8 foot ceilings, no dormers, replaced windows. A stated design load of 10,200 BTU/hr at 10F, against unit capacity of 15,200 BTU/hr, giving a balance point near 1F. That design load implies a coefficient of 1.89, and my corrected back-calculation from metered energy gives 1.82. Those agree to within 4%.

The house is real and it is unusually good. The owner also cross-checked their own coldest day against manufacturer rated power draw and landed within 1% of what the Daikin report said. Two independent routes, monthly and single day, imply a January COP of 2.63 and 2.59.

Effect. No calculation elsewhere on the site changed, because I had excluded the figure rather than used it. What changed is the conclusion I published about someone else's data, which was wrong and is now rewritten in the fieldwork note. The lesson I have taken is that "this number looks impossible" and "this number contradicts my assumptions" are different statements, and I published the second while believing the first.

How to report an error

Write to banerjeeashutosh01@gmail.com. Include the page, the number you think is wrong, and what you believe it should be. Confirmed errors are published here with both figures and the date they were fixed.