One Year of Improved Home Energy Use

Certainly one of the most impressive results of playing energy reduction "whack-a-mole". It is amazing to me that the far biggest use of home energy is just heating or cooling the whole house just so the temperature of the air in contact with our skin is in a very narrow range (for most of us). It looks like you are at the point of needing a revolutionary idea for any further progress.

This may be your next step:

DOE Solar Decathlon: Arizona State University and The University of New Mexico

 

Are the forced air ducts insulated?

Most of ours run through a crawl space, are readily accessible. The house was built in 1980, with forced air at the outset. Just a few years back we got energy efficient replacement windows, and I was on a bit of a roll, so started looking at the heated and return forced-air circuits:

They were in terrible shape. One return air vent in the living space actually went nowhere, just vented into the crawl space, lol. Much of the return air circuits were just voids between joists. Which isn't terrible, IF it's reasonably well sealed. It was a bit of a joke. There were voids between the sheet metal and joists, electrical cables running through the joints, massive amounts of dust and debris.

I pretty much lived in the crawl space for a couple of months. Ended up masticing, taping and insulating the heat side, and taping/sealing the returns. About half way through I got sick of the dust/grime, dragged a wet-dry vac down and cleaned the whole place. Also put filters on all our return air inlets, vac'd out everything I could get at.

 

I saw a air duct sealing system demo on "This Old House". They pressurized the whole system then sprayed in a sealant that coated ducts. It looked very impressive.

 

Watching "Breaking Bad" you'd get the impression it's pretty balmy, year 'round. We got the "barrel set", and it included a "making of" movie. It was an eye opener, watching set up for some of the scenes: actors waiting in parkas.

 

There are a couple companies out there that attach thin water jackets to the back of PV panels. Carrying away the heat can drop panels 40 degrees f. A panel will operate appx 10% more efficient when it's cool than when it's hot. The heat carried away (typically a closed loop/coolant) then warms your water, further increasing efficiency via utilizing heat that would otherwise be harmful/waste byproduct. Another mole whacked.
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Last night, my home PV system reached its first anniversary. Here is a daily production graph, also clearly showing when the original 1.6kW was expanded to 4.3kW:

Blue is actual production. The grey 'Estimated' line is NREL's estimate for a system of this size and orientation, accounting for typical local weather (cloudcover) but not for my tree shading, nor for the smaller capacity during the first summer.

My serious energy conservation efforts (beyond lowered thermostats and CFL lighting) began in 2006. Here is the progress so far in our all-electric (no oil or gas or coal) home:


Conservation measures included EneryStar hot water appliances (washer, dishwasher) and refrigerator, greatly reduced air infiltration through the building envelope, some improved insulation, a minisplit heat pump to displace most of the electric baseboard heat, and finally a heat pump water heater (HPWH) installed shortly after the solar PV was energized.

For the last year, the blue line is the net (billed) electric energy, the red line is gross energy consumption, including PV production. The decline of the red line represents mostly the HPWH savings, along with some additional reduced infiltration.

Total home energy for the year ended up at 5701 kWh, of which 2457* was produced by the PV, and a net-metered 3244 was purchased from the utility. Once the expansion portion reaches its anniversary, I'm expecting PV production to reach about 3600 kWh/year, dropping the net purchase to not much over 2000kWh/year.

(* The difference between 2457 kWh at the utility meter, and 2480 kWh at the inverters, is easily explained as conductor loss in the considerable wire distance between them. There might be some meter calibration difference too.)

This will also mean that our home's net energy bill will be $Zero -- we'll even end up with a rebate -- until June 2020, when the solar incentives expire.

Our home has technically been 'carbon neutral' since about 2008, when the local utility (90% hydro, ~8% other non-carbon sources) began buying enough offsets to cover its carbon fraction, including its motor vehicle fleet. Now I'm aiming for 'grid neutral' in a year or so. Best guess is, that will need a PV expansion to 7 kW. The roof has space for about 10kW, which should cover a future plug-in car too.

Two more conservation projects are being eyeballed -- improved attic insulation (partly for energy, partly to guarantee the fire sprinkler system never freezes, as recently happened to an acquaintance), and a SEDI (heat pump) clothes dryer, if and when that reaches North America.

Folks considering heat pump water heaters in the not-too-distant future should pay attention to the next generation, using CO2 refrigerant (R744). Some models tested locally, but obtained from the Australian market, tested out with far higher efficiency than anything currently available in North America. See Lab Test Report on Sanden Split System CO2 Refrigerant Heat Pump Water Heater

 

When I bought my house. I replaced the old 6 SER ac unit with a 12 SER duel fuel heat pump to my new furnace. Replace all the old crank out window a with dual pane gas filled vinyl, ripped off the old cedar Siding, added 1/2 foam board insulation and Hardie board siding. Replaced the leaky sliding glass door with a dual pain French door and the old wooden Front door with an insulated steel door and added a storm door.

Although I save about half on my gas bill (heat is taken care of by the heat pump till the temp goes below 36 then the gas kicks on) in the winter my electric bill did not go down one penny.

 

What we've done to our 1982-built home:

1) Light-colored (Pewter) roof shingles.
2) White exterior with green trim...instead of original dark brown/black colors.
3) ALL double-pane, argon-gas filled, solar-reflective windows installed.
4) Replaced original HVAC with new high-efficiency, dual-stage HVAC system.
5) Replaced original HVAC ducting (which had disintegrated) with new higher R-value ducting.
6) Installed removable, light-colored (Adobe), 90% Solar Screens on sun-facing windows.
7) Replaced ALL incandescent lamps with LED lamps.
8) Installed home weather station sensors in rooms to permit room-to-room temperature monitoring & measurments.

And, daily, I read & plot our electrical power consumption, so that I can predict what our monthly use and bill will be...and usually within ±1-2%!

 

I also had all my old duct work changed, except for the "hard pipe" and that was wrapped with insulation with outer foil. I need to add attic insulation. If you do nothing else, that is the biggest bang for the buck.