Conservation first in a low-carbon home

The below description of actions taken by a MA-based homeowner shows just how much you can do by being attentive to energy use in a home, before adding things like heat pumps and solar panels.

I have reviewed cursorily your well researched and detailed Green plan. I would only offer, from my less informed point of view, a slightly different perspective for you to consider. If it appeals, perhaps you could devise tables and guides to make it useful for those in similar situations to mine. 

Your thrust, as I interpret it, is to “invest” in actions that reduce the use of fossil fuels by the most efficient means available, taking into account cost and payback.

My approach is two-pronged, namely 1) Conservation and 2)Investment in Efficiency. 

For example, my house, built in 1957, 3169 sq. ft. living area, 2×4 walls, 2x 8 floor joists, and 2x 10 rafters has been insulated and weatherstripped thru a MassSave contractor, (walls were too narrow to add insulation). Windows are double pane, insulated. Blower door tests showed a reduction from 5k CFM to 3.5k. 

Oil-fired hot water baseboard, which I put in in 2000, 12k LG mini-split, 3-ton Trane central air for the upstairs, connected to existing ductwork. Electrical panel is 100 amp.

Electricity usage, 3600kw/year. (Note that I pay about $0.43/kw, due to fixed delivery charges and add ons). Oil, about 400 gal/yr. Propane c.40gals/yr

To reduce carbon footprint, thus save money, we two occupants keep doors closed, in rooms we either don’t use, or wish to heat comfortably while occupied, supplementing with electric space heaters. We keep the heat “off” in the second floor heating zone, save for briefly bring temp up to 64 at bedtime. Hot water source is via propane stove heated kettle, save for necessary ablutions, or guest visits when we keep the 40-gallon hot water heater on. (Runs off the oil furnace)

Each year I look for ways to lower our electrical and fuel needs without impacting lifestyle. For example, I have always felt it unnecessary to run the 40-gallon hot water heater, off the furnace. I did winter/summer Hi-Lo setbacks on the furnace temp, and used the furnace on/off outside of heating season. Then, Last year I installed a twenty gallon electric hot water heater which serves nicely in place of the forty gallon one for about three seasons. It’s also installed closer to the bath/shower, thus avoiding a need to draw off any cold water. (We must do that with the large HW heater, but save the water in a bucket for plants.). This winter, I added another fuel saving step. I attached an on-off switch to the furnace powered hot water heater, thus powering it up the few times it’s needed each week. I figure this saves not only fuel, but the corresponding electricity necessary to run the burner. 

With virtually no exceptions, we air dry the two loads of laundry each week, either clothesline or air dryers in basement and in front of wood burning fireplace insert .

I do expect to have to replace the 3-ton central air unit at some point, even though the replacement compressor is only ten years old. The coolant, I learned, was ordered “discontinued” by the US government, in 2010. How Trane was allowed to sell me a new unit in 2013, I will never know. Last year I had the unit serviced, and was charged $400 for one pound of coolant. Thus, I have decided to keep it going until it dies, unserviced, which could last another ten years, given that it only lost one pound in the first ten, and the services did not detect the source of a leak. Be that as it may, I’m prepared to spring for a mini split replacement, which will be far more efficient and cheaper to run than the central unit. (It will also save on fuel oil in the heating season).

Oh, and as an FYI, for emergencies I have two portable generators, 3500 and 4700 watts which hook into relays powering everything in the house.  

Six sixty-gallon water barrels supply water for plantings, garden and lawn outside, car washing, etc. 

One final point. Today’s footprint analysis could take into account auto use, as EVs are part of the equation, and one must consider “fueling” at home. At some point I expect battery storage will be advanced enough, so a small solar collector could supplement the mains for charging and supplementary utility, like lights, TVs, etc. in an emergency situation, or for charging an EV.

All Electric Condo Renovation – replacing ducted heat pumps with ductless.

Our All Electric Home

I know from our experience that one can a) use heat pumps with no fossil fuel backup in our New England climate and b) taking certain measures (those “variables”!), can make all electric heating (and cooling!) “affordable”.

We live in a good situation for home energy comparisons — a condo development with 26 almost identical two story duplexes built in the mid 1980s with all electric heating (no gas or oil).

Each home had two big heat pump compressors at the side of the building with one heat exchange unit in the basement serving the first floor and one in the attic serving the second floor, both providing forced hot (or cold) air through ducts. There were also a few (we had three) baseboard resistive heat units installed in areas hard for ducts to reach. The old heat pumps could also use resistive (expensive) heating if they could not keep up.

Around 2014, our Eversource bills told us we were consuming far less electricity than our average nearby neighbors.

No doubt this was because we already did these:

1- Had energy efficient lights and appliances
2- Turned off items when not needed, including light polluting outdoor lighting
3- Dried our clothes on drying racks rather than in the dryer
4- Kept the thermostats low and wore warm clothes in the winter
5- Opened windows in the evenings and closed them in the mornings during cool summer nights, rather than than using the AC
6- Avoided wasting hot water when showering or washing dishes
7- Disconnected the wiring to our inefficient resistive baseboard heating units

All the buildings have had Mass Save coordinated improved air sealing and attic insulation installed, an important measure.

In 2015 we sought to do even better, by installing a single ductless mini split and stop using our ducted system at all.

We installed a single 15K BTU ductless mini split in our living room, an open area near the kitchen. (cost after rebate about $3,600) The installer argued this would be insufficient for the whole house but we wanted to try it anyway.

After 2015, we used only this one mini split for heating and cooling for the whole house. We kept the living room at about 68 degrees in the winter. Enough heat drifted up the stairs to the second floor to keep it cool but usable for two bathrooms, office and bedroom at around 62 degrees in the winter. We had absolutely no heat in the basement which is cool (but not close to freezing) in the winter, being largely below ground. We were and are satisfied.

With that change to the mini split, our electric bill was 28% lower for 2016 than it was for 2014.

If we had chosen to put a mini-split in each major room, the installation cost, after rebates, would have been much higher and the operating cost would also have been higher.

We know we are paying 1/2 or less of what some of our condo neighbors are paying, as some have shared their electric bills with us. Our biggest electric bill of the past year was for January 2023 for $308. One neighbor paid over $1,100 for that month! None have chosen to replace their ducted systems with mini splits.

Other factors to consider:
• We are just two retired persons
• Philosophically, we are fine with a bit less than 100% comfort.
• We do not inhabit the basement
* Larger families would probably need more mini splits and use more energy • Our 1st and 2nd floor lived in area is 1,200 sq feet.

In Conclusion

Our “minimalist” approach may not be for everyone, but it was very affordable and we feel good about having less of a carbon footprint than probably any of our nearby neighbors. If one used this minimalist approach switching over from gas heat to a mini split, the outcome should be the same

Note: Our percentages and numbers have been adjusted to remove the impact of the two EVs we charge at home. Also, once in a while as a treat for the coldest winter evenings, we run our wood stove for a few hours, but that has been a constant over many years and would not affect the reduction numbers we saw in 2016.

Heat pumps in very cold weather

Hi Alan, sorry to be so late getting back to you on your experience with heat pumps. I believe we are both right at the same time. Under some circumstances (fairly modern, well insulated construction with internal party walls like in your condo) you can get by on heat pumps alone if you can tolerate some cold days in winter. If our house was at 65F I would be divorced. I might be able to squeak by on heat pumps alone if I could tolerate 65F. But I can’t keep our detached home at 70F on the heat pumps alone if it is below about 20F out. I manage this very carefully (eg I put the furnace on for an hour) and have got our annual heating oil use down to about 30 gallons a year. Before the “Fab Four” it was 3,000. So even a detached house at 70F is very close to being able to be heated year round in MA with heat pumps alone. Even if it can be done, it gets very expensive because heat pumps get less efficient at low temperatures. The economic cross over point (the temperature below which it is cheaper to heat with natural gas) is often around 30F. So, even if it can be done, it is very expensive to do so. 

Back up generators, heat pumps and V2H (vehicle to home) charging

The question on generators is timely. I have a very old generator that I can no longer get parts for. It no longer works. I ordered a Tesla Powerwall battery to be integrated with my solar panels to replace it. I cancelled that when I realized that the Ford F150 Lightening is designed to be a back up generator for a house. After 2 years on order, the Lightening was delivered in October. One way to use the Ford as a back-up generator (which Ford recommends) is to have their solar/battery partner, SunRun, install the battery/inverter/charger hardware for you. Unfortunately this costs $10k. However, the F150 comes with a 30A/220V electrical socket in the bed of the truck powered from its 130kWh battery. This battery is the equivalent of 9 Tesla Powerwalls. This is designed to act as a back up generator. Because of my existing (defunct) generator I already have the wiring for the emergency panel and the transfer switch. If you have had a generator in the past then you have this wiring too. I had my electrician install a connector on the side of my house which connects the truck to the emergency panel. It was a little tricky to get it running, but I now have 3 days worth of power during a grid outage. This is not running the heat pumps, I still have my oil furnace for these occasions. If I were to run the heat pumps on the Ford I would probably trip its breaker and, even if it did not trip, the battery would last maybe one day. 3 days of power is great if you are home, but we also go away for up to two weeks. The Ford’s battery will not last 2 weeks. Hence I am going to get my electrician to install an automatic transfer switch so that the Ford’s battery is only used when the grid is down.

An alternative is to install the battery/inverter/charger with your solar panels. Ask GS for a quote on this. If the battery can be recharged from the solar panels during a grid outage then even a much smaller battery (like a Tesla Powerwall) could power your house for a very long time, though probably providing enough heat from the heat pump to keep the house from freezing rather than keeping you toasty warm. Ask them what their experience is on this. Especially what happens at night (will the panels produce enough electricity during a cloudy day in winter to charge the battery enough to provide heat at night), and what happens if the panels are covered in snow.

I have explored many different option for batteries and generators. There is no perfect solution and all solutions are expensive. You can cover some scenarios for providing power during a grid outage, but there is no solution that covers all scenarios, particularly ones where you are away for long periods and we also have a grid outage that last more than a day or so.  Remember that gas-powered back up generators regularly fail to start in cold weather (even if they have been regularly serviced, I speak from experience) and run out of gas. 

I think the F150 with an automated transfer switch is the best option (for us) because it is relatively cheap (maybe $1,000 on top of the Ford) and can last 3 days even with thick snow. But this only works if your EV supports home charging. Today only the F150 really does (Nissan claims the Leaf can but I am skeptical), but most manufacturers (including Tesla) have announced that they will support vehicle-to-home (V2H in the lingo) in the future. If you see an EV in your future, which you mentioned you did, this is likely the best option. However, it could be a few years away and that means you need a back up plan for heat in arctic cold weather during a grid outage before you get the EV with V2H. The realistic options are a gas-powered generator (with enough output to run the heat pump) or a propane heater.