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Comment by bake | Hacker News Reader

Hi HN -- We’re Baker and Calvin, two heat pump nerds who are really excited about home electrification and its impact on climate change.

During our explorations, we realized really struggled to find good calculators out there for understanding the impacts a heat pump can have on your specific home.

So… we built one! It’s free to use, and we’re curious to get your feedback.

Feel free to try it out here, and let us know what you think!

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It doesn't seem like the chart of costs includes the effect of summer A/C.

And the chart that is shown peaks in winter a couple months early.

Overall, it seems to significantly underestimate my energy costs.

The conclusion is also confusing: it says I would save $89/year or $24K in 15 years. Huh?

$89/year doesn't seem like enough to justify any investment, and $24K is about $1600/year or ~95% of my current costs, which seems too high to believe.

This is really good feedback, thank you -- the "$24k" number is something we're going back to the drawing board on, we're reaching too much there. That number includes the capital costs of replacing and installing equipment (a single heat pump vs. both a furnace and an A/C unit, for example, plus rebates), and it's best case for heat pumps vs. worst case for legacy equipment. So, I think you're right, it just doesn't line up sensibly with the really concrete annual energy savings numbers.

On winter peaks, I'll have to look into what you're seeing -- we pull weather data from the nearest ASOS station to your zip code and have done a fair bit of validation on that data, but it could be a number of things. If you're interested, you could send the inputs you're using to pumpers@heatpumpshooray.com and I'll do a little digging?

FYI, we just updated that section of the results to hopefully be clearer and, when it comes to the total lifetime savings including equipment costs, a bit more conservative.

From the "calculator" the default "heat to" temp is 68. That seems kind of absurd to call a default indoor air temperature during winter months. Is used for all day or just night time temps?

This is about what we do in our house. Is it absurdly high or low?

It's very low for a daytime temperature. Maybe it makes sense with the gas crunch and energy prices in europe, but the specific thing that bothers me about it is hiding that number below the "advanced" checkbox. I don't think people who are used to paying for winter time heating set their thermostat to 68, so using that number to calculate how much a heat pump costs to run will artificially lower the cost of the heat pump in this calculator.

I'll take a look back at the residential energy consumption survey and the exact distributions.

The Manual J (industry standard approach to load sizing) uses 70 dF for heating and 75 dF for cooling as its defaults, so we could definitely update the defaults to those, too.

Even in warm sunny California I don’t know a single person who sets their heater above 70°.

I'm in Colorado and have the furnace set between 63-65 in the winter by choice, nothing to do with cost

I also live in CO and have it at 64 at night and 68 during day. Very comfortable.

Wouldn't a higher winter temp create more savings when switching to a heat pump?

I guess I can try their model and find out.

68f is 20c, I honestly don’t know anyone in the UK who has their thermostat higher than that. I know plenty who have it lower though! Is it an energy-cost thing?

This is awesome! Must have been a lot of work.

Thank you so much! It was a truly great learning experience, and definitely more to go.

On iOS at least, expanded ducts are showing as $15 (despite adding the more reasonable $15K to the total). Similarly, a panel upgrade is listed as “$1,000 to $3” despite adding the (slightly light) $1K-$3K to the upfront expense summary.

Rotating the display to landscape shows the full numbers, so it’s a styling issue, not a content issue.

I was hoping to see an air-to-water calculator as hydronic heat is common in New England. If that equipment wasn’t so premium-priced and hard to find experienced installers, I think a lot of conversions could happen.

Roger that! We're hearing the desire for hydronic / air-to-water systems and support for Europe / elsewhere from a few different places, so this is helpful. Note for those in Europe, we're using local energy prices and local grid emissions in addition to local weather, so we'd need to expand those to cover additional geos as well.

And thanks for catching the issue on mobile, we'll get that fixed asap.

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