Green Part 2: Electrification

Our goal is to completely remove all gas use from our home. This means electrifying domestic hot water generation, cooking, and house heat (plus our car). Luckily, electrification is no longer a hard thing to do – and we will soon be trying to get PG&E to completely remove the gas line from our property.

Cooking with Electric: We will be cooking on an induction stove, which is an amazing way to cook (completely different from old-school radiant electric stoves). It's a more efficient way to cook (with no wasted heat), it avoids putting toxic combustion gasses and particulates into your living space, and it's way easier to clean. The Bosch model we ordered was back ordered for MONTHS (again, Covid - but also evidently demand for these amazing stoves has been ramping up).

Our Bosch induction stove - well worth the wait!

Clothes Washing and Drying: Our space was super limited, plus we didn't want to have to pull in 240v power, and we didn't want to have to vent the dryer -- so we were excited to learn about the all-electric LG All-in-One washer/dryer combo from Steve Mann on a tour of his Berkeley Passiv Haus. The washing machine works great. The dryer can take a while, but it is nice to put in a load and come back hours later to find clean, dry clothes!

Domestic Hot Water: We chose to use a SanCO2 air-water heat pump to generate our hot water. The SanCO2 unit is particularly interesting because its refrigerant gas is CO2 -- which has an interesting thermodynamic cycle that allows you to generate very hot water in a single pass. (Another huge benefit: if the CO2 happens to leak, its greenhouse effect is a tiny fraction of other commonly used refrigerants.) We chose to combine a 120-gallon storage tank with this heat pump, so we could generate hot water during the day and still have enough to use overnight and first thing in the morning. A further benefit of this system is that the SanCO2 unit is entirely self-contained -- all I had to do was plumb two water lines between the unit and the hot water tank (no refrigerant plumbing needed). See Green Part 8: The Smartest HVAC on Earth (Harvest) for an update on Domestic Hot Water

Air-water heat pump on the left, 120-gallon storage tank with 5-gallon expansion tank on the right.

HVAC/Space Heating: This is where everything gets really interesting. We replaced our gas-powered furnace with an AirScape makeup air unit (originally designed as an add-on for giant efficient homes, it operates like a car radiator with a fan). Working with the support of Dan Johnson at Beyond Efficiency, we designed a hydronic heating system for the house that uses the SanCO2 domestic hot water system to supply water to the AirScape. (AirScape is currently the only unit on the market that can do this with potable water.) This means we can use a single heat pump to generate both domestic hot water, and heat the house -- so we can afford to spend a bit more (the SanCO2 costs approximately $5,000) to get the most efficient technology. It also allows us to benefit from using thermal storage; this helps minimize our electrical needs when the sun is not shining, and will keep the entire house comfortable using the 8 kW of solar we are able to generate from the roof of our small house. The single heat pump can be programmed to make sure the tank is filled on a schedule, and to not run unless absolutely needed during certain time windows.

AirScape Residential Make-up Air Unit - with fan and filter

One additional feature of our system is that it can be set up to draw air from outside through carbon filters, to over-pressurize the house with clean air. Here in California, which now seems to be perpetually on fire, we (sadly) anticipate this may be a significant benefit.

See Green Part 8: The Smartest HVAC on Earth (Harvest) for an update on Domestic Hot Water

Solar + battery: Before we can install solar panels, we will first need to clear out all the roof protrusions, to maximize the roof area on the south-east side for solar generation. (This involves rerouting the drain vents to the north-west face, and permanently removing two vents for the gas furnace and gas water heater.) The roof over our rear porch will also use a few special solar panels, which are designed to look good from both sides. We hope to install about 8kW of solar that will be facing south-east and west, to help generate power over more hours in a day. We will also install a battery to provide power overnight for the house.

Electric Vehicle: We have been EV drivers for years, and can't imagine ever driving a smelly, inefficient gas car again. As renters, we charged our EVs for years just using a simple 110v outlet. Here, we have been able to install a Clipper Creek level 2 charge station (cost: $600), with an adaptor that allows us to charge our Tesla Model 3. (Fun fact: a new Model 3 costs the same as a new Toyota Avalon, or Chevy Bolt.)

See also Green Part 3: Insulation and Gray Water and Green Part 4: Goodbye Gas Water Heater (and Gas Meter!!), Hello Closet