Heating is a significant source of greenhouse gas emissions. An electric heat pump is an efficient, economical, and fully electric way to heat your home – which means that if you use a carbon free electricity source, emissions will be minimal.
When we bought our fixer-upper house, it had an oil heating system. Think if it as basically a diesel furnace that sends the fumes out the chimney. The fuel was stored in a giant metal tank buried under the back yard patio. The thing heated the house up quickly but that was its only virtue. It was either on or off, leading to large swings in temperature, it was loud, it was expensive to refill, and most of all it’s an environmental nightmare. It produces the most CO2 of any method of heating your house.
One rainy day, our sewer line got backed up. We called a plumber to come with a sewer snake, and he cleaned it out and got the water flowing. When he was done, he told us that he smelled oil in the sewer line. Well, that got my attention. When we bought our house, we signed up for PLIA insurance (Pollution Liability Insurance Agency), a state program which pays for remediation if you buy a house with an oil leak. They told us to call a testing company, and a couple months later we got soil tests completed.
Yup, the tank was leaking oil into our yard and the soil was contaminated. Oh crap.
PLIA paid for the clean up, but the remediation company needed to send an excavator to dig out the area under the brick patio. I took the bricks up by hand by myself and stored them in part of the driveway. We also needed to raise the carport for the excavator to fit. I called a metalworker and he did it for something like 1.5 grand.
With the old furnace gone, we needed a new heat source. We settled on a Mitsubishi Electric Heat Pump, supplemented by a natural gas fireplace. In terms of comfort, I consider this top-notch. The heat pump keeps the temperature at a nearly constant level. In addition, the air handler allows us to run the fan without heat or AC, which is quite useful at times since the top of the house heats up with the sun during the summer while often times the main floor stays cool.
Heat Pumps work like air conditions, except that they can run in both directions. In the winter, the system makes the house warmer by making the area around the outdoor unit a bit colder. Ours is installed so that it blows the cold air over the top of our driveway, which I must say has no effect whatsover on our lives. In terms of energy usage the heat pump is quite good. It is rated at the Energy Star Tier 2 Level. I’ve read online that the energy cost is about 60% less than that of heating oil. Also, since its being run with zero carbon electricity, it’s effectively a very low emission method of heating the house – provided that there are no refrigerant leaks! It will be important to get it serviced regularly both to extend its life and ensure that no refrigerant leaks occur.
I’ve found it very difficult to figure out exactly what it costs us based on my energy bill, since we replaced an ancient and highly inefficient electric stove with a new gas stove at the same time we switched heat sources. The net result was that the electric bill went up by maybe 20% and the heating oil bill went away entirely. The oil furnace had run around $1700 per winter.
The difference during the months of December and January was about 11 kWh per day. At 12.32 cents per kWh for 62 days, that adds up to $84 to heat my hose for those two months compared with probably around $350 for heating oil for the same period.
Something that jumps out in the graph above is the month of March. We had a freak snowstorm that lasted for about 2 weeks. The system is not so efficient at freezing temperatures, thus the larger bill. We used the gas fireplace liberally during this period too. If you live in Seattle, this kind of incident is rare and the December / January time-frame is more represnetative of normal experience. If you live in Minnesota or Alaska, you’ll probably want a Natural Gas furnace for the coldest part of winter.
Some considerations about using a heat pump:
- The Mitsubishi heat pump functions all the way down to 0 F, but is a lot less efficient at freezing temperatures. The gas fireplace comes in handy in those situations, but we didn’t want to leave it on overnight. The result was a big electric bill for that month.
- It comes with a programmable thermostat. We set ours to always stay above 65 F so the doggie stays happy, but turn the system off entirely when on vacation. It automatically kicks down at night to save us energy.
- The system needs to be connected via lines that contain refrigerant, which run through our basement. The lines go to the air handler, which is connected to the existing ductwork. To make the system more efficient, I got a bucket of duct sealant and some foil tape and sealed up the ductwork. I’ve also slowly been wrapping the ducting in insulation. I stared with the foil wrapped fiberglass stuff and then switched to the bubble wrap duct insulation, available on Amazon. The job still isn’t quite done yet – its taking a long time. See below.
- Another thing to think about in an old house like ours are the windows. We replaced a few where the seals had failed and some other single pane aluminum windows. This certainly helps with the heat problem.
- The heat pump was not very well secured by the guys who installed it. It’s bolted to cement and also fastened to our fence – good enough for noraml life but probably not good enough for an earthquake. I plan to add another post a secure it there too to keep the thing from toppling over if the big one hits.
If you are replacing an existing heating system with a heat pump, you can get a rebate of $1200, or up to $2000 from the city if you are ripping out an old oil furnace. I believe we paid around $10,000 (net) for ours and took out a loan from Puget Sound Cooperative Credit Union at a fixed rate of 4% to pay for it. The heat pump has an expected life of around 20 years. Being a finance geek, I did the math and calculated that given the energy savings and a 4% cost of capital, the heat pump was a positive NPV project. It’s the right decision both financially and for the environment.