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8fingerlouie

I'm a european (with a heat pump), but i tried it anyway.

I entered :

- Zip 56714

- 2500 sqft

- 4 occupants

- 1 boiler

- no aircon

- natural gas

and the result was :

Switching to a heat pump will increase your cost by... $257.28 per year

So i'm not entirely sure it works as you intended, or natural gas is much cheaper than electricity. Over here, Natural gas is currently at €2.96/m3 (about 2.5x the price last year), and every calculation we've made based on the heat pump vs natual gas shows it will reduce our annual bill by about 50%.

I've had the heat pump for 6 months, and while it was spring/summer with reduced need for heating, the total consumption of the heat pump in those 6 months has been around 900 kWh, and i estimate around 2000 kWh for the winter. (2000 sqft house, well insulated compared to US standards)

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Hi! Yes, couple of primary things that would drive that answer:

1/ Right now, if you select "No A/C", we still include the cost+emissions of cooling from the heat pump. It's on the backlog to add a "heat vs. heat only" comparison. In part, we're assuming that if you have cooling capability, you'll probably use it (and therefore wanted to include that in the emissions impact), but also that homes without A/C today will have small cooling loads to begin with, so it wouldn't change the answer too dramatically. For now, I'd suggest looking at the monthly costs in the summer on the bar chart and mentally adjusting the headline number for those. Sorry that's not smoother!

2/ Natural gas is indeed way cheaper here -- dramatically so this year, but previously as well. The backtest shown on the site is Feb '21 to Feb '22 -- natural gas prices this coming winter are bound to be much higher than they were last year, so savings numbers will definitely change going forward. It's on our list to (a) make that dynamic clearer on the site, and (b) explore a more forward-looking savings number. Right now, the annual energy costs are "what you would have saved _last year_ vs. your existing equipment", instead of what you might expect, thinking that would be more convincing / less controversial, albeit potentially conservative.

Thrilled to hear you're 6mo into life with a heat pump! Is it air-to-water and still using water/steam radiators, or forced air now?

> Thrilled to hear you're 6mo into life with a heat pump!

It was the logical thing to do. Even before the war in Ukraine, the ROI of the heat pump was 8-10 years compared to natural gas. With current conditions, shortage of natural gas, inflation and more, the ROI is around 4 years.

> Is it air-to-water and still using water/steam radiators, or forced air now?

Pretty much everything regarding heat in (northern) Europe is based on water, with the exception of hotels that usually use either only air or a combination of air/water.

Our particular installation is from the 1970s, meaning it's 1 string and made for much higher flow temperatures than the houses from 2000 and onwards, so instead of a 35C flow temperature we instead have a 55C flow temperature, which reduces the COP value of the heat pump.

My particular model (https://www.vaillant.com/home/products/air-to-water-heat-pum...) has a COP value of (up to) 5.4 with a flow temperature of 35C, which gets reduced to around 4 with a 55C flow temperature.

I've coupled mine with radiator thermostats from Tado (https://www.tado.com/gb-en/products) which use geofencing to lower the temperature when nobody is home, and they also have a "sensor/control unit" for the heat pump control itself, allowing fine grained control of the heat pump. One of their upcoming features is to try to optimize heat pump usage for when electricity is cheap.

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