I will admit my wife and I are empty nesters, and we spend about two months a year abroad. The house is pretty efficient. R-30 in the 6" wood-stucco walls and R-40 Owens Corning insulation in the attic. Lighting all LED, HE whole house fan, HE A/C, LG frig-freezer, Maytag washer/dryer, and attic fans. I suspect keeping the attic as cool as possible in the summer keeps the A/C cycling down to a minimum. House roof is concrete tiles, which you can cook on in the summer. Inside the house, we have also installed wooden shutters on all triple pane glass windows. We can easily maintain a 25ºF differential between outside/inside with no A/C. As a side-note, the solar is installed on the ground. Besides maintenance and cleaning, the air circulation on the bottom of panels keeps them far cooler and more efficient than if they were mounted on a sizzling roof of concrete tiles. They also face 180º south. No other tricks.
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Tankless water heaters are terrible....
- Thread starter nwdiver
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- Energy Environment Policy
I will admit my wife and I are empty nesters, and we spend about two months a year abroad. The house is pretty efficient. R-30 in the 6" wood-stucco walls and R-40 Owens Corning insulation in the attic. Lighting all LED, HE whole house fan, HE A/C, LG frig-freezer, Maytag washer/dryer, and attic fans. I suspect keeping the attic as cool as possible in the summer keeps the A/C cycling down to a minimum. House roof is concrete tiles, which you can cook on in the summer. Inside the house, we have also installed wooden shutters on all triple pane glass windows. We can easily maintain a 25ºF differential between outside/inside with no A/C. As a side-note, the solar is installed on the ground. Besides maintenance and cleaning, the air circulation on the bottom of panels keeps them far cooler and more efficient than if they were mounted on a sizzling roof of concrete tiles. They also face 180º south. No other tricks.
We've encountered many days of near 110ºF and currently have the thermostat set for 72º but it doesn't seem to be coming on much. Last month's electric bill was a mandatory $4.96, my share of grid maintenance I guess. Edison tiers down to three now, 16, 25, & 32 cents. Also have ceiling fans in every room except the bathrooms running on summer cycle (counterclockwise).
CameronB
Member
I have a whole-house gas-powered tankless water heater. Yes, it did require a one-time gas pipe upgrade to install but since then has been mostly trouble free. Just me and my wife typically but we have had many house guests (sometimes 6 or 7 at a time, using all 3 of the bathrooms simultaneously). It can handle hot water needs for the whole house even at full tilt, which is nice. Our average gas bill is about $7 a month - that covers gas for the tankless hot water heater, cooking (a commercial style Viking unit) and our gas powered clothes dryer. So the monthly cost of the water heater is negligible, especially when it's just two of us. But even we have longer term house guests (which themselves often have kids), gas bill is still generally around $12. So nothing too expensive. And having always available "endless" hot water even with two people taking showers simultaneously and someone else washing clothes...is something I would have a hard time letting go of.
As usual in discussions like this, it is more a matter of what best fits your personal situation, and less like black and white, good and bad. I have in good conscience, professionally recommended, tanked and tank-less, electric, gas, propane, oil, heat pump, integrated with home boiler, point-of-use and centralized, solar, and more.
Some things to note:
* Pipes are usually under- or non-insulated. Remedy this.
* COP of heat pump water heater looks awesome, but if it is in a heated, or semi-heated location, that efficiency comes at the cost of your heating system (and the efficiency of the heat pump is now less than the efficiency of your heating system).
* Efficiency does not necessarily correlate with operating cost. I have seen people upgrade to gain 10% efficiency, by switching to a fuel which cost almost twice as much per BTU.
* It's complicated, consult an unbiased professional if you are unsure.
* Conservation almost always is the best improvement for the buck.
Thank you kindly.
Some things to note:
* Pipes are usually under- or non-insulated. Remedy this.
* COP of heat pump water heater looks awesome, but if it is in a heated, or semi-heated location, that efficiency comes at the cost of your heating system (and the efficiency of the heat pump is now less than the efficiency of your heating system).
* Efficiency does not necessarily correlate with operating cost. I have seen people upgrade to gain 10% efficiency, by switching to a fuel which cost almost twice as much per BTU.
* It's complicated, consult an unbiased professional if you are unsure.
* Conservation almost always is the best improvement for the buck.
Thank you kindly.
SageBrush
REJECT Fascism
Thanks. PVwatts says LA should expect 1.6 kWh/watt*annum so you are outperforming by ~ 20%
My array is also ground-mounted with SE optimizers so I want the same!
In its first year, I did about 4% better than what PVwatts estimated for my area. Coupled with two-month vacations and the other efficiencies, I probably saved another 13-14%. Every little efficiency adds up, especially with windows, attic work and pulling the cool air in, up, and out through the attic in the early evening. Ya, the whole house fan, even good ones, can be a little noisy but the master bedroom a bit away from the fan. Finally, I shower at least once a month whether I need it or not........
SageBrush
REJECT Fascism
That is my line about haircuts.
My interest is your high PV generation. Your low use I understand.
Actually, I don't live in L.A. I live about 80 miles northeast of L.A. in the high desert, where we get about 300 days of sunshine when L.A. and the beaches stay socked in with a cloudy coastal eddy that doesn't burn off until late morning. On many days, my LG panels will perform slightly better than the PTC rating. Not a lot but better. But no, my PVwatts value wasn't derived from any zip south of the San Gabriel or San Bernardino mountain range. Maybe that helps.
Xenoilphobe
Well-Known Member
mspohr
Well-Known Member
Looks interesting.
I'm looking to replace hydronic heat and hot water heater and this looks like a good option.
Every heat pump water heater on the market is a 'hybrid' design. They have resistance elements for backup. I agree there are niche applications where tankless heaters are more appropriate but in general any application where a traditional water heater is in use a heat pump can offer a replacement with no change in overall convenience. What bothers me is when tankless heaters are marketed as 'more efficient'.
If unlimited hot water is the goal then ideally you could put a tankless heater downstream of a heat pump heater... best of both worlds
That's interesting, I was thinking along those lines for my future house...
I am currently at the stage of collecting ideas / concepts for designing my retirement home that I want to start building in the near future (should be completed in the next 3 years). I want to build a passive-solar house: lots of heat-capacity inside using materials picked for that purpose, very good insulation outside, south facing triple glazed windows with good R factors.
Since I live in Canada, for the cold winters here the passive solar design will have to be augmented with a ground heat pump (aka "geothermal") system. For water heating, I was planning to use a combination of solar water heaters on the roof (with insulated tank for storage) and tankless "booster" near the faucets to reach desired temperature in case the stored water temperature is too low (winter nights).
Ideally, it would be best to combine the roof-top solar water heater + ground heat-pump system and use the tankless booster only as a last resort.
I am still at the stage of collecting / researching information, so please let me know if you have any suggestions / ideas / links I should consider.
Thanks!
Cheap Solar PV has rendered Solar Thermal completely obsolete for all conventional applications... ESPECIALLY for northern latitudes where freeze protection is required. $200 of PV + $1300 of heat pump will save more energy than $2k spent on solar thermal.
A ground sourced heat pump should be all that you need. There are ways to split the well to provide heat for your home and water.
The GeoSpring was terrible. I talked 4 people into getting one... we had a ~120% failure rate (the replacement also failed). It has terrible reviews. Rheem makes a model that is way better.
Ulmo
Active Member
I'm glad to hear Rheem is making a decent product.
Does it have scheduled heating? I'd like it to heat more in daytime, and let the temperature drop more in nighttime, so that it doesn't decide to reheat at night when it is most inefficient. Also, I'd like to be able to have it use some attic heat when it makes sense. Also, if it can do smart grid stuff like turn off when the sun ducks behind a cloud of the nearest utility's solar farm and turn back on when the cloud goes away, that would be great.
SageBrush
REJECT Fascism
DHW and space heating are a bane of my existence. Decent construction engineering along with PV, heat recycling, and heat pumps would cut their energy use down dramatically, but instead I am saddled with an NG furnace and floor radiant heating.
Sawyer8888
Member
We had a Rheem heat pump water heater installed about a year and a half ago. I haven't run all the numbers, however it functions very well in comparison to our previous standard water heater. We went with the 80-gallon option because we didn't want to run out of hot water when guests were in town. So far, it hasn't disappointed.
The Wi-Fi capability has had limited use for us, however I can connect via Wink as well as the standard Rheem app. Wink allows a schedule to be setup. When guests are here, we can quickly choose the "High Demand" setting.
One of the coolest features is that our garage stays somewhat air conditioned. The heat pump pulls in surrounding warm air and pumps out cool air. Your Tesla will thank you during the summer months. As mentioned, the efficiency of these units excels in warmer climates, like South Florida.
Our first Rheem heat pump water heater had a fan on it that made a tremendous amount of noise right out of the box - just shy of 80 decibels. Rheem's customer service was very helpful in getting it switched out via Home Depot. The second unit is much much quieter.
When I inquiried, a few plumbers and my regular A/C technician told me that they see a lot of problems with tankless water heaters - maintenance-wise. They do not recommend them for that reason and because their cost vs. a regular water heater or heat pump doesn't make sense. But again, every situation is different, so yours may prove that a tankless is the way to go.
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