Energy Cost Tracking Through Decades of Actual-Cost Data, Charted in Microsoft Excel, Two Example Homes

This post is a further challenge of home energy-efficiency rating as a home owner asset for real estate purposes.  Why shouldn't we just rely on actual operating costs as measure of home energy efficiency?  (Google that, and the question is not recognized. Far down the results, a UK EPC, Energy Performance Certificate  is discussed; and no, it is not on-topic.) 

For any home, there is no better measure of energy efficiency than actual utility-cost data. That data will have complexity. Whatever, it will be more real and inspiring than transitory numbers of some rating scorecard. Every improvement or degradation nullifies a score; cost data is perpetual.

Where cost-tracking is continuous, it becomes useful for verifying effects of a continuous process of home improvement and varied usage. Is a new appliance working correctly and as-claimed? What costs are seasonal, or dependent on the number of house occupants? A home energy score is if anything, a drag upon making changes.

Here is a display of monthly data of natural gas usage in my now-a-rental home, for the past eighteen years:

Annual totals for July through June heating seasons are more informative. 

See that through 2012 with the house unimproved and kept chilly in Winter, I tolerated annual cost of about $460. Improvements from 2012 to 2016 reduced the natural gas cost by half, still with Winter thermostat setting of 55°F. From 2019, the house has been a rental with an average of two occupants and comfortable thermostat setting, with return to annual cost of about $460. See that extreme economy is met with increased importance of base charges, and bills are reduced less than expected. Results with careful weatherization are unambiguous, when accomplished scattered over time. A very big further improvement is still needed: replacement of the like-new high-efficiency gas furnace with a heat pump unit. As with everything else I have done, this will happen with study, with work done and documented by-myself except the final commissioning. I hope to find a good  Heat Pump Coach , as advocated in today's email feed of Onward Oregon . I hope I will be favored with early access in this, for my role as a reporter. I aim to be a good reporter in the similar matter of Heat Pump Water Heater evolution, where I have coped with an early-technology failure. I learn by doing my own work, but must not fail to benefit from a depth of experience.

Now look at to-date electricity usage:

Large consequence of a  heat pump water heater failure is evident in  tracking of electricity consumption in my now-rental home. Large electricity savings with  a 40 gallon Rheem Professional Prestige ProTerra Hybrid Electric Water Heater PROPH65 T2 RH375-SO, were wonderful, for one year. I have detailed the factory-offered repair in replacement of the control board, which did no lasting good.   Electricity usage rose to a brief historic high at year-end 2022. At last the 40 gallon Rheem HPWH was scrapped.

Such an undignified end for my "exceptional" first-try HPWH. Nothing in the nearly-new unit was of interest for salvage. Rheem provided a replacement at no cost except that of increasing size from 40 gallons, to 50 gallons. Perhaps renters used exceptional amounts of hot water, that forced generation with resistance heaters. A bump-up in size might not help, but give it a try.

House in transition, it will take several months to know that weird electricity consumption is at an end, with this brand-new 50 gallon Rheem heat pump water heater.

PRO H50 T2 RH310UM

SN 0322208450

Wall Pads; that's what I'll call the four wood assemblies that, with ropes, secure the position of the tank in the event of an earthquake. The 40 gallon tank was 20.25" OD. This is 22.25" OD. To accommodate the change, I reshaped the painted-white 2x4s, and moved each pad assembly an inch away from the walls corner. I am serious in belittling the steel straps sold for this. What, really, do they anchor to? The 3/4" plywood at the wall is anchored to the wall studs by 3" deck screws. How could steel strap-ends conveniently align with wall studs? Earthquake loads are lateral, for sure splitting the  studs at bending lag screws. Here with diagonal 1x8 shiplap behind 5/8" drywall and very many pad screws, this tank is anchored.

Isn't this an exceptional installation?










At April 2024, note new professional acclaim of this Rheem model, by highly-followed YouTube creator Matt Ferrell: https://www.youtube.com/watch?v=abGiNL9IT54

See that with vent and drain plumbing behind the wall, in the now-conditioned crawl space, it was easy to create a new P-trapped drain for HVAC. The little Tygon tube for high-efficiency gas furnace condensate, no longer dangles across steps to a utility sink. The convenient dedicated drain will accommodate more drainage from heat pump HVAC.

With the new 50 gallon HPWH, in time, I expect to see lasting return to annual electricity cost of about $500 per year. Judging that electricity consumption is not seasonal, prefer annual totals for calendar years. 

Conclude that with two-person occupancy as a rental, my well-documented energy-efficient home has annual natural gas cost of about $470 per year. The total electricity cost is also  about $470 per year. Elimination of natural gas service would reduce natural gas cost by about $200 per year, and increase electricity cost by about $100 per year. The home draws about 4000 KWH per year, ahead of a conversion to heat pump HVAC.

Can I know how my house measures up to standards? A resource of interest to me in learning tried better methods of house construction - - is Portland, Oregon 501 (c)(3), Earth Advantage . I look to them now.

Compare energy efficiency of my well-improved 1000 sf house, to that of a 832 sf super-well-built single-story ADU built in Portland in 2020. Consult this training video , at time 9:31:

$45 per month energy cost, per-year, scaled to 1000 sf: $649 per year. Presume that the EPS-label energy cost is the sum of electricity and natural gas costs.  For my house that sum is a bit less than $1000.

I hope that Earth Advantage collects and studies actual-cost data, now two years of it here. A score that has physical meaning, is interesting.

My house has room for doable improvement, probably by less than $200 per year. Compared to neighboring homes, mine surely is very efficient.

Actual Decades-Long Cost Data for Another Home, Where I Improved the Attics

A two-story Ranch home in Sandy, Oregon:
Now begin charting for another home with extensive energy usage data, that of my older sister, whose house has also been improved by my weatherization.  I look for proof that my work produced savings, and seek to learn more about what constitutes good record-keeping, and charting in MIcrosoft Excel.

This is a two-story home well-built in 1973, 2052 sf conditioned space. Heating is also natural gas, with no air conditioning. Expect natural gas cost to be more than double that of my 1000 sf single-story home, with nearly-same electricity cost.

This home and its natural gas usage history were described in a previous post, October 23, 2012, Making Sense of Gas Usage History . There see detail of very-substantial attic floor sealing and added insulation.

An additional decade of data is interesting. Was the Winter of 2020 exceptionally cold; or staying warmer and healthy in the epidemic? This home used more than twice as much natural gas than mine, from the same supplier, Northwest Natural, and at reduced dollars per therm. There were years before the weatherization where fewer therms were used. Were they exceptionally mild? What happened in 1997? Whatever the complexities, I think the charting is a rewarding exercise. We're doing good things. What will we see if now there is conversion to heat pump HVAC? History matters.

See annual natural gas usage of about 1200 therms, $1000, as expected.

See electricity usage well-tamed by LED lighting and technology improvement in appliances and connectedness to information, costs steadily declining, while approaching a doubling of electricity rates.

The annual electricity cost is nearly double that of my 1000 sf single-story home. That's a bit surprising.

See consistent Excel charting with some different trial of logic for colors.

Interrupted Energy Savings With My Rheem Hybrid Heat Pump Water Heater

Rheem Professional Prestige

Pro Terra Hybrid Electric Water Heater

PROPH65 T2 RH375-50

S/N Q 272 026 175

Publicizing defect of year-2020 Control Board Part Number AP21386 Rev 00 and, perhaps, associated thermistors. Offering hope of the durability of replacement Control Board Part Number AP22260 and replacement thermistors Part Number SP20845.

Electricity usage in my rental home has spiked since April, 2022. A problem was evident to me in charting the April billing. Quite amazingly a problem was suggested in early-June by my electricity provider, Pacific Power!. Electricity usage had been down 40% for fourteen months since HPWH installation in February, 2021.

For three months, all of the savings were cancelled, running on resistance heaters with periodic automatic attempts to revert to Heat Pump Mode. Now-repaired and seeming to run reliably 100% in Heat Pump Mode, I hope the charting of electricity usage will again inspire others to replace their ordinary electric or gas water heaters,

Here is the chart at 12/2/2022:

And here is monthly tracking by Pacific power, leading them to again notify excessive usage.

With the notice of excessive usage, Pacific Power offered this conservation advisory:

PP_Power-to-Save-wattsmart-Handbook.pdf

All that is potentially helpful is a table at page 4 of 15:

I am overdue to find savings in a HVAC heat pump, and that is not a factor in excessive usage now, except that we must not resume usage of a window air conditioner next Summer. Renters have never used electric space heaters.

Counseled by Rheem, we viewed the condenser plates, finding normal dry conditions; no icing. The HPWH smoothly running in Heat Pump mode chilling the garage, is then dismissed of involvement in unusual draw of electricity except that, maybe someone is taking really-long showers.

We tripped the circuit breaker feeding a proper cable underground to a Shed on 12/4/2022 for whatever reason, as the least bothersome next step. Daily usage did not change. We are wanting again the energy-conserving usage for same months a year ago, for the month of November 2021: 431 KWH, 13 KWH per day, $51 billed, instead of that for

November 2022:  954 KWH, 28 KWH per day, $99 billed.

Something is still very much amiss.

Rating my interaction with Pacific Power, I suggested that they should care to know what is happening. I had asked: Could I log demand on each circuit breaker? Answer: No. 

I am not keeping up an Excel chart of July 2022 over smaller time scale, that better illustrates history associated with the Heat Pump Water Heater:

Now return to the naive beginning of this post:

New renters were unaware the unit was running in Electric mode,The garage was not being nicely refrigerated in Summer heat. Quiet in the garage was not alarming.

Half-way through a three month incident I was at last painfully aware, and driven to find a repair. I was the installer. The unit was sold to me by General Pacific, Inc. a large supplier of parts for industrial electrical equipment to Bonneville Power Administration and also a low-cost supplier of heat pumps and more to area weatherization contractors. I buy and install many  Panasonic bath fans, with pricing 30% below that at Home Depot. The Rheem HPWH was a one-off for myself.

Who to I call? I talked with a competent plumber at Portland's "Water Heater King" store where I am a good customer, and learned there are large problems with the Control Board, being resolved by Rheem at no cost. Just call the Rheem heat pump service people in Montgomery Alabama, at 800-995-0982 weekday daytime hours. Get parts and do the repair myself. The parts offered are the Control Board, Part Number  AP22260, and three identical Thermistor Kits, Part Number SP20845. 

Thermistors? They are supposed to be ultra rugged. How could they fail? I would try just replacing the Control Board. Still, get a look at the thermistors. Detach power leads and detach the tank lid with its ten screws,

See little resemblance to a GEN 5 THERMISTOR REPLACEMENT diagram among materials emailed by Rheem. The work area is on the far side opposite the Control Board. The tank cylindrical wall is very much in the way. Cylindrical foam insulating jackets held by many zip ties must be removed and are found bonded to thermistors by gooey thick adhesive wrap.

A Rheem YouTube video will be shared days later but will be of little help:

Rheem hybrid thermistor access

Go ahead now to replace the Control Board. It is all of the black expensive-looking control interface and display, up-front as I oriented the tank. Pry off a cover. Remove two screws. Extend many leadwires to view connections at the backside.

View the backside of the replacement board. I will hold the boards side-by side and move connectors one at a time.

Wires as found with a minimum of crossings.. Swapped leads may not be as neat.

Back together and seeming to be solidly in Heat Pump mode. Next morning though, I will be called by a Rheem technician, advising for the first time that the thermistors must be replaced. Some unique identifier associated by a past alarm, causes thermistor rejection ever-after, regardless of control board replacement. Something like that. All advice is verbal. Each new conversation is with a different Rheem call center person, trained with a different set of knowledge.

First swap the thermistor easiest to reach, "Suction," on yellow leads.

Higher up on the same pipe, swap a thermistor from blue leads, Discharge.

Each thermistor kit has three new clips to choose from. Learn that the clip removal or attachment is thus with a twist.

Gray leads, Evaporator.

Repair completed. I had worked atop a piece of 3/4" plywood resting on the tank cylinder wall and the heat exchanger, doing no harm. The work areas are inconveniently close to the cylinder wall and the heat exchanger. It was never intended that a home owner would do this. I could not replace the six cable ties I cut. In the factory, this tidy assembly might have been completed before the tank cylinder was applied. The odd object at right hand is my banged-up work light propped at the tank wall edge.

I am offended by large pieces of gummy material, two pieces four inches square, not the same as butyl strips about one inch square applied in the factory to better couple a thermistor to adjacent tube surface temperature.  The huge squares are not scored for separation to useful size.

At two places on each thermistor kit box, there is warning in effect to not touch the dangerous gum. I will treat the nasty squares as needing professional disposal. Not in my trash. I will mail them to Rheem, with complaint, as a pdf printing of this blog post.

What does the warning mean?

www.p65warnings.ca.gov is vague here. Is risk only with ingesting or chewing the gum? I won't touch it.

If thermistors are a repair item, the factory wrap of tubes and thermistor should be a thick fabric with velcro strips. No foam tubing and zip ties. Surely there are incidents of disastrously cutting a leadwire somewhere, reaching blindly with sharp snips. 

Avoid any need of cancer-causing gum.

Study the principal guide for consumers here, 

Use & Care Manual

Rheem AP21681 Rev 02

Rheem randomly sent this PDF as an email attachment,  following one phone conversation. Now a Google search brings nine results, none the guide. Therefore, I store a copy in Google My Drive:

 Rheem AP21681 Rev 02

The troubleshooting and repair parts listings did not imagine the control board failures now occurring. Nothing I have done here is mentioned.

It is odious that one offered solution here while under warranty, is free replacement of the entire HPWH. There's a lot of bad carbon in that. Repairs must be offered at no cost for at least twenty years, the least lifetime I think is reasonable for a water heater. The consumer trust thus guarded is essential to needed adoption of a HPWH, in every home, well-subsidized again in the Inflation Reduction Act of 2022,

I await honest statements from Rheem about what is happening. Why the thermistor swaps? Is there a better solution in circuit board recognition of sensors surely still good, avoiding replacements.

Electricity Savings With A Heat Pump Water Heater

I am eager to share proof of projected 40% electricity savings, in replacement of an ordinary resistance electric water heater, with a beautiful heat pump water heater, HPWH. The installation was reported in post an exemplary heat pump water heater.

 

I have the unusual resource of a chart going back 22 years. This chart through December 2021  includes a full year since the water heater replacement. Savings are very evident, seeming to be the expected 40%:

From 2012 to 2018, there was remarkably little need of electricity, me living alone. Demand might have been met with a modest photovoltaic array but for neighboring trees to South, and adverse West facing of the major roof surface. For the past four years, occupancy and electricity demand have doubled, with two wonderful renters in this 1955 home now fully weatherized and modern, radon-free. It is a rare rental opportunity, managed with some originality. All utility costs are auto-paid by me. The renters pay a fixed total of $200 per month for electricity, natural gas, water/ sewer and trash/ recycling, balanced annually against actual payments. Where I see the costs and share pain, I am moved to do all possible to reduce costs; thus the HPWH.

I believe charts showing control of somewhat-voluntary expenses, can be rewarding and inspiring. And, yes, they can be dispiriting if not achieved. We wonder why monthly utility bills include charts such as this of the October 2021 electricity bill:

There are many variables of weather, behavior and occupancy, in monthly bars. Why a December spike? Visitors? October comparisons pre- and post-HPWH 278 kwh vs 390 kwh, a drop of 29%, is as expected, but probably under-states actual savings accumulated. Is that really 40%, as hoped?  Sometimes the trends in this bar charting, are concrete.

From my Excel file:

See annual savings of about : ($680 - $460.)  $220, a 32% reduction of annual total dollars. With $220 per year savings, $18 per month on average, the material total cost of $577 (plus my free labor) is repaid in fhree years. If the water heater serves twenty years, the present value of the annual savings, applying my Perpetuity Math, is $24,000. What a good deal!

In January 2022, find the deal quite diminished for a new investor. My $399 purchase in November 2020 was of: Rheem Professional Prestige ProTerra Hybrid Electric Water Heater PROPH65 T2 RH375-SO

https://www.rheem.com/product/professional-prestige-proterra-hybrid-electric-water-heater-proph65-t2-rh375-so

Offered today at homedepot,com, $1199 after $500 discount:

https://www.homedepot.com/p/Rheem-Performance-Platinum-50-Gal-10-Year-Hybrid-High-Efficiency-Smart-Tank-Electric-Water-Heater-XE50T10H45U0/312742081

 Local distributor General Pacific offers this unit is $1658 minus $500 = $1158, not a compellingly better deal. Equivalent models from Rheem and from AO Smith, cost the same,

Energy Trust of Oregon in its public web site doesn't bother to promote the heat pump water heaters it subsidizes with public funds, while subsidizing flimsy LED light bulbs with far less savings potential, I think the HPWH promotion is very muddled and.is probably not working, The better bargain two years ago was a missed opportunity too, I suppose. We should be moving these by hundreds of thousands, involving DIY home owners as well as contractor allies of Energy Trust..Maybe slow motion is a factor in ballooning  cost.

Failed promotion of heat pump water heaters is a big disappointment to me as an advocate of affordable rental living (my house as exemplary). I am so happy for what I have done. Who else even thinks of this?

Here post updates of the monthly electricity usage tracking, ever more clearly the dramatic savings with the HPWH. Hot water is much more nearly "free", not proportional to the number of house residents, perhaps more free than with some rooftop solar collector, that would be badly oriented, shaded by a neighboring tall Douglas Fir. 

For a house that could "go solar", a heat pump water heater must be key in being solar-ready.

an exemplary heat pump water heater installation

Here is my new heat pump water heater installation, for assessment by the reader. I have responded to new demands, exceeding those of the cheap electric heater now recycled. It is taller. Water pipes to the tank are longer, yet are simpler and more secure. Thoughtful cradles at last support against tip-over in an earthquake roll. Behind the drywall, at both sides of this room corner, house shape is stabilized by 1x8 shiplap sloped 45°; now benefitting the tank seismic support. I know where the wall joists are, from nail locations on interior drywall. At the cradle assemblies, the larger pieces of 3/4" plywood are set with long screws finding wall joists if I am lucky. Rely actually upon 1 5/8" deck screws engaging shiplap, strong for lateral loads, to carry seismic loads from the cradle assemblies.  The cradle assemblies adjusted to best tank position, are bonded to the bigger plywood pieces and to the shiplap directly, with 2" deck screws.

A new, simple, dedicated plumbing drain, serves the pumped drip of a condensing gas furnace, as well as the flood of HPWH condensate. Users, the wonderful renters of my home, have informed choices to readily make upon hot water temperature and economy of mode. They will be pleased by more than 50% savings of energy for hot water, amounting to more than $20 per month. I am pleased to have achieved this prideful conservation at material cost of just $577, where the well-rebated $1200 heater cost just $399.

Learn more in this job photo album. See that I have followed manufacturer instruction that tank water lines not atop the tank, so distant from wall connections, should be flexible PEX. PEX couplings at the tank are wrench-detachable without need of oddly-prescribed little metal garden hoses having dangerous quickly-releasable face seals.  The tank is tied to cradles well-anchored upon diagonal shiplap behind the drywall. Condensate is directed to a dedicated plumbing drain. 

Here are the Rheem graphics of expected installation. My installation is superior in having the Cold shutoff very accessible with an inherent heat trap within the wall; isn't that true? I don't understand the thermodynamics of this.

Google the title of this post, to see if residential HPWH installation standards exist.

Find these videos:

A 2014 installation by This Old House has odd, simpler HPWH installation of an unidentified unit where tank piping is at the top.

How to Install a Heat Pump Water Heater | This Old House

Federal resources of Bonneville Power Administration are offered through Hot Water Solutions, an initiative of NEEA, Northwest Energy Efficiency Alliance.

How To Install a Heat Pump Water Heater: Professional Version

How To Install a Heat Pump Water Heater: Consumer Version

See that side-mounted water connections are a common innovation with heat pump water heaters, Manufacturers should align against destructive plumbing code that demands tank connection with at least 18", not more than 24" flexible metal hoses. Could anyone defend need of that? Every added connection adds cost and failure risk.  Please find marked-up Plumbing Code for State of Oregon. I find fault too, with seismic requirements. Big steel straps have no value without intelligent anchors. If slack permits a heavy tank to roll with momentum, straps are doomed.

At 2/27/2021 add reference to installation of a SANDEN CO2 found in this Matt Risinger YouTube video. Choose an outdoor unit if you can, for the better efficiency and quiet.

Start viewing at 12:00.

Find an overview of heat pump water heaters, by Matt Risinger, Top 5 Heat Pump Water Heaters, July 2020.