Methodology
How heatpump.blue works
Three real-world inputs go in; one temperature, and what it saves you, comes out. Here is what each input is, what we don’t model, and exactly where the data comes from.
What goes in
- 01
About 15 years of hourly weather, near you
We use roughly a decade and a half of real hourly outdoor-temperature observations from the weather station closest to your ZIP code, so your result reflects how many hours your winter actually spends at each outdoor temperature — not just one “design day.”
- 02
Your model’s own published cold-weather data
We look up your exact heat pump by its certified model number and use its published performance at a range of cold outdoor temperatures, not a generic assumption that every heat pump behaves the same way in the cold.
- 03
Your utility’s rates
We use your electricity rate — including time-of-use pricing if your plan has it — and your furnace fuel’s price (gas, propane, oil or none), scoped to your utility where we can identify it from your ZIP code.
What comes out
One outdoor temperature: the switchover point that costs you the least over a typical winter, and the exact setting name for your thermostat. We also show the range around that temperature where the cost difference is small, so you know how precisely the number actually matters, and what your current thermostat setting is costing you by comparison.
What we don’t model
- A full room-by-room heat-loss calculation of your specific house — we estimate it from what you tell us.
- Demand charges, solar, batteries, or humidity and defrost behavior in detail.
- Any future change to your insulation, equipment or rates — the result reflects today’s inputs.
- Your exact utility bill — published rates can miss riders, fees or a plan change since our data was collected.
Treat the result as a well-informed estimate for planning and for setting your thermostat — not a guarantee, and not a replacement for your installer’s judgment about your specific equipment.
Data credits
NOAA Integrated Surface Database (ISD)
Hourly weather-station observations across the US. US government work, public domain.
US Census Bureau ZIP Code Tabulation Areas (ZCTA)
Geography used to locate your ZIP code and match it to the nearest weather station. US government work, public domain.
US Energy Information Administration (EIA)
State-level residential electricity, natural gas, propane and heating-oil prices. US government work, public domain.
NREL / OpenEI utility lookup
“U.S. Electric Utility Companies and Rates: Look-up by Zip Code” (2024), National Renewable Energy Laboratory, via OpenEI. Licensed under Creative Commons Attribution 4.0 International (CC BY 4.0).
Manufacturer and certification test data, via rebate.blue
Published cold-weather performance for certified heat pump models, looked up by model number through rebate.blue, a sibling .blue product.
Who runs it
heatpump.blue is published by DotBlue LLC, a UniCo Group company. It is free and works anywhere in the US. UniColorado Heating & Cooling, a sister company, installs heating and cooling equipment in the Denver, Colorado area. About heatpump.blue
Analytics
We use Google Analytics, PostHog, umami and Cloudflare to see which pages and features get used, so we know what to improve. Besides page views, we record events such as a tool run starting, a result being shown (its kind and confidence), a request to UniColorado being sent, a link being shared and the compare tool being used. Privacy lists everything the site collects.
Get your exact number
Enter your ZIP, your heat pump model and your rates, and get the lockout temperature that costs you least, with the range it is sensitive to.
Questions
- Does heatpump.blue model my exact house?
- Not a room-by-room model. We estimate your home’s heat loss from what you tell us (size, age, insulation level and similar), which is enough to find a cost-optimal switchover temperature, but it is not a substitute for a contractor’s room-by-room load calculation before buying or sizing equipment.
- What does heatpump.blue not account for?
- We don’t model demand charges on commercial-style rate plans, solar or battery interaction, humidity or defrost behavior in detail, or changes you might make to your home’s insulation. We also don’t guarantee your utility’s published rate exactly matches your bill — riders and fees vary.
- Where does the weather data come from?
- NOAA’s Integrated Surface Database, a public-domain archive of real hourly weather-station observations across the US.
- Who runs heatpump.blue?
- DotBlue LLC, a UniCo Group company. The tool is free and works anywhere in the US. UniColorado Heating & Cooling, a sister company in Denver, installs only in Colorado.