How We Fully Electrified Our Very Old House

Heat pumps are a great upgrade.


This year, we did the best upgrade ever. We ripped out the fossil fuel innards of our house and put in a high tech, fully-electrified heat pump system.

It was easier than we thought, and had so many benefits: 1) a cleaner, healthier house; 2) lots of recaptured usable space; 3) air conditioning; 4) good for the planet… we ditched gas, with option to fully power the house via solar and storage in the future.

Here’s how we did it, step by step.


The House

Here’s our house as originally built in 1890. It’s a simple design, with some Victorian touches like tall windows and ornamental trim. It was likely heated with coal, and had a windmill to pump water.

Our house before electrification, around 1900

Now here it is today, still mostly the same: the original plaster and lathe, doug fir floors, redwood windows, ornamental trim, and more. The new high tech stuff is inside.

Our house after the heat pump upgrade

Why We Upgraded To All-Electric

We’re into antiques and using good old stuff forever. But after 130 years of fossil fuel heating (including gas furnaces installed in 1993), it was time to switch to a cleaner system.

We wanted to get methane gas out of the house completely, given what we’d learned about its health endangering and climate destroying properties. We’d already replaced our gas stove with an induction range, so just needed to replace the furnaces (about to die anyway) and hot water heater.

We also wanted to support the growing home electrification ecosystem with our dollars, so the whole global process of decarbonization can go faster. Many people would just buy another gas furnace, which is what most HVAC contractors recommend (it’s most profitable for them). We wanted to help break that cycle.

We must decarbonize and electrify faster to fight climate change
Just do something… we need to decarbonize much, much faster.

Key Lessons Learned

Choose a contractor with electrification experience. We only considered heat pump electrification specialists. Any contractor can buy heat pump hardware, but it takes expertise to design and install a system that will be effective, energy efficient, and reliable. Our contractor, Eco Performance Builders (of Concord, California) knew what they were doing and were also very collaborative and open to ideas.

Choose a design that takes advantage of this smaller, better technology. Since heat pumps and their line sets are so much smaller than gas furnaces and forced air ducts, you can really get some big wins in an old house if you’re creative about recapturing space.

Keep it as simple as possible, labor is 80% of the project cost. Heat pump hardware is relatively cheap: $1,500 each for a few condenser boxes and blowers, etc. The bulk of the cost is the installation labor, ripping out your old systems and installing the new ones. So don’t make your contractor do unnecessary work, make things as easy as possible for them.


Step 1: Designing The System

We got design proposals from two different contractors, each of whom walked though the house, did specialized measurements, and asked lots of questions.

Both proposed a ducted system for our first floor, because there was plenty of room in the basement for ducts. One proposed a ducted system for upstairs, and the other proposed ductless (wall units). The ducted system would be more efficient, but ductless would give us individual temperature control in each room.

Our three new heat pump condenser units after the upgrade.
Our three outdoor units (condensers): left to right for upstairs, downstairs, and hot water heater.

To back up for a minute, here’s how most heat pump systems work. There’s an outdoor unit called a condenser (aka heat exchanger or pump), which is connected via fluid and power lines to an indoor blower unit (the fluid carries the heat or cool).

The indoor unit can be wall mounted, or an out-of-sight blower connected to the rooms by ducts. Both ducted and ductless systems are called ‘mini-splits,’ because the systems are ‘split’ between outdoor and indoor.

We decided on the ducted system upstairs, because four wall units was too many, and we valued the extra efficiency of a ducted system more than room-by-room temperature control. Plus, there was plenty of space in the attic for new ducts.

For downstairs, we counter-proposed a ductless system because we wanted to recapture basement space, and realized we could heat the whole floor with just two wall units. Moreover, we planned to re-do the floors at some point, which would disrupt a ducted system. Finally, there was no obvious place downstairs to put a large air return for a ducted system. Our contractor thought ductless would work fine, so that’s what we did.

Electric heat pump wall unit from Fujitsu.
One of our downstairs ductless wall units, near the ceiling.

Our gas hot water heater also needed to be replaced. We chose a Japanese made (Sanden) system that’s high efficiency and uses a more climate-friendly refrigerant (CO2) than most heat pump water heaters. It was expensive, and I worry that the manufacturer is really small (hope they stay in business). But it works great.

Here’s all the specific hardware we went with:

  • (Downstairs) Fujitsu ASURLF1 ductless, 1 condenser and two wall unit air handlers, 18 SEER 9.5 HSPF
  • (Upstairs) Fujitsu ARURLF ducted, 1 condenser and one attic platform air handler, 20 SEER 11.5 HSPF, plus a MERV 13 filter and R-8 duct work with total leakage of 1% or less.
  • (Hot Water) Sanden CO2 83 gallon high efficiency heat pump water heater with a 3.75 Energy Factor

The final design piece was figuring out where the (2″ diameter) line sets would run outside the house from the condensers to the indoor units. For the downstairs units, it was easy to run a few feet of conduit up the side of the house to the wall units without being too noticeable.

For the attic air handler, the contractor was able to thread the line set up the side of the house through the existing 3″ diameter pipe that previously vented the gas fumes from the basement up through the roof. This was an elegant solution – you can’t see any change at all.


Step 2: Upgrading The Electrical

We only had 90 amp service to our house, which wasn’t enough to support three new heat pump system circuits (15 amps each) plus our car charger, induction range, electric dryer and everything else. So we needed an upgraded service entrance (the box that houses the meter and power from the street) plus a new master load panel in our basement, and some new dedicated circuits.

Fortunately, PG&E (our utility) didn’t object to us upgrading to 200 amp service. Sometimes they will, or will ask for a big fee, on the grounds that their existing wiring or transformer can’t support the extra load. For us it was a relatively easy switch, with the power only out for four hours.

A big side benefit of upgrading the electrical was getting our infrastructure grounded properly and making it safer. The existing service entrance from the 1960s had some questionable wiring.

We also wanted it to support solar, storage, and software-driven power management in the future. After a lot of research, I concluded that the new ‘smart panels’ weren’t quite ready, so we went with the best traditional hardware we could find (from Siemens, who along with Schneider and Eaton seem to dominate this category). As with HVAC, the hardware is cheap; installation is 80% of the cost.

For system monitoring, instead of spending thousands on a new-to-market smart panel, we did take a $300 flier on a Sense Energy Monitor, which has been both worthwhile and enlightening.


Step 3: Removing The Old, Nasty Gas System

The first couple days were the most intense, with a large crew demolishing our two gas furnaces and hundreds of feet of bulky ductwork in the basement and attic. They also removed the old attic insulation, and the old plywood boards covering it up. And they ripped out all the gas piping in the basement, all the way back to the gas meter.

It was obvious how dirty and dusty all this ductwork was, and great to see it hauled away. It had probably been blowing bad air around the house for years. Don’t let anyone talk you into re-using old leaky and dirty ductwork!

Getting rid of those old bulky dirty gas furnace ducts saves a lot of space.
Some (but not all) of the old ductwork we ripped out of the basement and attic.
Gas furnaces headed to the recycler.
Gas furnaces headed to the scrapyard… good riddance.

One big challenge was getting the two large metal ducts out of the central chase that ran up the center of the house from basement to attic… they were wedged in pretty good. This was a huge, 2.5 foot square space we really wanted to completely clear out so it could be repurposed (more on that later).

Old gas ducts removed from central chase to save space.
We removed these two large ducts running 30 feet from basement to attic, to free up space.

Step 4: Installing The New Hardware

Once the old ductwork and furnaces were out of the way, the new lightweight system could start to go in. First came the condenser and tank for the new water heater. This system circulates water from the inside tank to the outdoor unit, which then heats the water and then sends it back to the tank to be used.

Next the first floor HVAC system went in. Each wall unit was mounted as high on the wall as possible, since they blow heat downward to distribute it efficiently. This meant punching a 2″ hole in the wall behind each unit, through which the line set (electrical and fluid) could be threaded outside, down the side of the house and through the basement (along the joists) to the outdoor condenser.

Once the line sets were run, and everything tested and working, the first floor could be air sealed and insulated from below (we had no subfloor so this meant patching and then sealing the original floor boards).

Installing a heat pump wall unit.
One of the guys punching the hole and mounting the bracket for a wall unit.

Installing the upstairs (ducted) system was more involved. First, the attic had to be air sealed. And because the house was originally balloon framed, there was an air gap around the perimeter of the attic which had never properly been sealed (below the eaves) and needed to be closed up.

Next, new registers had to be cut above each room for the new duct system, and the old registers plastered over. They were near the outside walls, but for energy efficiency we needed registers nearer the center of the house, to minimize the duct run lengths from the air handler. We also needed to cut a new, large air return (20 by 30 inch) into the ceiling above the upstairs hallway, to make the system quieter and accommodate the 2″ MERV air filter.

Air sealing the attic before installing heat pump blower for ducted system.
Air sealing the attic before the new air handler platform and ductwork is built.

Once the air sealing was done, the plywood platform for the attic air handler could be built. Then the new duct system was connected to the air handler and the registers.

Next, it was time to blow in twenty inches of cellulose insulation to cover the attic system, bringing the total R-Value to R-20. The attic used to be nice and clean, but now it looks like a snowstorm hit up there!

Finally, the thermostat could be installed, the system balanced and tested, and we’d be done. Except it didn’t work that way. Both the Fujitsu condenser (outdoor) units the contractor initially installed turned out to have faulty components. One was replaced immediately, but another part took a few more days to come from farther away, so we had to pull out our flannel sheets and down comforters for a couple of cold nights.

The contractor was great: they really stood by their work and were persistent about getting everything right, including the little details. Special kudos to Ryan, the crew manager. Whether it was doing an elegant visual job with the line sets, patching the holes well after ripping out the gas lines, figuring out how to vent the new Panasonic motion-sensing bathroom fan, or accommodating my many techie questions, they were just great to work with.


Step 5: Using The Recaptured Space

After the HVAC crew had come and gone, there were still more wins to be had. The space formerly occupied by the gas furnace ducts (which ran from from basement to attic) was ready to be repurposed.

We hired Mike, a great carpenter, to build a linen closet upstairs in the old chase. Soon we’d actually have a place for sheets, pillowcases, towels and toilet paper (if we could find any).

Note that we did consider other options for this space: laundry chute, dumbwaiter, dog elevator, and sliding firemen’s pole. I was outvoted on all of them.

Here’s the before (right) and after (left) picture of the linen closet.

Recapturing gas furnace duct space for linen closet before and after.
A big bonus from our systems upgrade was recapturing this former duct chase for a linen closet.

Finally, here’s a shot of all the newly usable space in our basement… where the two gas furnaces and their bulky ductwork used to live (including the ducts that went all the way to the attic). I didn’t expect how dramatic this change would be.

Sanden heat pump hot water heater in new clean basement free of gas furnaces.
Our new, clean, spacious basement – formerly crammed with dirty furnaces and ductwork.

Epilogue: This Was Totally Worth It

Since we finished the upgrade, it’s been really cold as California winters go. The new system is working beautifully, the house is nice and toasty, and the quality of the heat feels better. Its great to have all the extra basement space too.

The whole project took five weeks and was one of the best tech upgrades we’ve ever done. It feels great not to be using any gas at all. The heat pumps use more electricity, but our utility bills will still be lower than they were with the leaky old gas system. And we’ll have AC this summer.

The utility bill savings alone don’t justify doing this project. But if you factor in the value of the AC, the extra space, of being part of the climate solution, and of being fully electrified so we can go off-grid with solar and batteries if needed in the future, it’s a big win.

Of course we also put a lot of time into this, as early-adopters do. But hopefully we’re at the front of a wave: a new technology that’s better, cheaper, lighter weight, healthier, and crucial for the planet.

Hope you’ll consider trying this yourself… it’s a great upgrade!


Getting rid of methane gas is great, meter is now ready to be removed.
Our old gas meter, now totally disconnected. Come and get it, PG&E.