Hydronic vs. Heat Pump

I recently had a ductless heat pump installed, primarily for cooling in the summer. As an added bonus it provides significantly quieter heating in the winter compared to my hydronic system that relied on radiators and noisy fans in the walls. Although it's only been a few days I couldn't resist taking a look at some data to see how using the new system has changed my home's energy use.

It's tough to do an apples-to-apples comparison since my old system runs on natural gas while the new one is all electric. I took a look at my electric and gas use for a pair of days, one before the new system was installed and one after. My electrical use went up by about 70%, while my gas use was down by about 64%. In terms of the dollars, Seattle's low electricity rates mean I saved about 32%. However, since my solar panels generate a surplus of power that State law requires I forfeit every spring, I'm able to increase my electricity use by about 50% annually without paying any extra money. This new ductless system essentially runs for free thanks to my solar panels.

It was also interesting to see how the ductless system draws power. It runs a lot more often than I expected! My base consumption seems to be up about 30W thanks to the constantly (but quietly!) running fans on the indoor units, while the heat comes on several time an hour and draws about 1kW. When the installer tested to make sure that the AC works the system pulled about 4 kW!

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