Electrification of Home Heating/Cooling
-Sonja, SunWork Volunteer
Heating and cooling your house is one of those things you don’t think much about until the temperature starts to dip in the winter months or peak in the summer months. Our house, a 1400 sqft single story in Sunnyvale, had a natural gas central heating system but no air conditioning. For the hottest summer days it was not uncommon for the temperature to reach the mid 80s inside. Even though there is some insulation on the roof, the very low slope means it has no accessible attic space to easily add more. Another complaint my family had was the furnace, located in a closet central to the house, right next to the dining room and bedroom. Being an older model it was loud; so loud you needed to vacate the dining room if you wanted to converse without shouting across the table. It was time for a better solution.
Since our goal was to improve both the heating and cooling inside our house, a heat pump space heater was the ideal solution. An Air Source Heat Pump (ASHP) is much like an air conditioner except that, in addition to providing cooling, it can be reversed in the winter months to provide heating. It is a two-unit system. There is an outdoor unit that either heats or cools a refrigerant fluid. That refrigerant is piped to the indoor air handler unit which in turn blows conditioned air throughout the home’s duct system.The heat pump we chose is a variable speed Mitsubishi PUZ-A30NHA7(-BS) and the air handler is an ultra quiet Mitsubishi PVA-A30AA7 with a supplemental Electric Heat Kit EH05-MPA-MB. Our HVAC installer removed the old natural gas furnace and repurposed that closet for the air handler and supplemental heat kit. All three units run on electricity so our installer capped the natural gas line that was previously used by the furnace. Our final cost for equipment and installation came in just under $12,000.
Our utility company provides 100% carbon free electricity, so we now heat and cool our house in an environmentally-friendly way. Plus, by eliminating the combustion of natural gas we are improving our indoor air quality and our health.
Single Zone or Multi-Zone
In our situation, because we already had ducting throughout the house, it made sense to reuse the existing ducting to distribute the conditioned air. This is known as a Single Zone system. However, a centralized duct system is not the only option; you can also eliminate the ducting and use a mini split to condition a single room or a section of the home (aka Multi-Zone system).
Living with a Heat Pump
As of this writing my family has been through a full heating and cooling year. The ultra quiet air handler has been a dream come true in terms of its whisper quiet operation. Our outdoor heat pump unit, being able to operate at variable speeds, has also been pleasantly quiet – a great benefit since it is located immediately outside a bedroom window. The heat pump has performed perfectly in keeping our house comfortable year round – especially compared to our previous summers when we did not have air conditioning. One adjustment we needed to make is our expectation for how quickly the heat pump is able to heat the house. Compared to our old furnace, the heat pump takes more time to get the house up to temperature. As a result we have adjusted our thermostat to keep the house in a more narrow temperature band and to start heating the house sooner in the mornings – an easy enough fix with a programmable thermostat. Switching away from natural gas and towards electricity for our home heating/cooling of course means we are spending less on natural gas and more on electricity. As our lifestyle becomes more and more electrified, it has turned our attention to our next home improvement project, adding a solar PV system!
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SunWork is piloting the installation of ultra-high-efficiency electric heat pump water heaters to replace fossil-fuel-burning natural gas water heaters in Bay Area homes.