Questions tagged [energy-efficiency]

The percentage ratio of energy produced to energy supplied to a system; or a measure of minimum energy required relative to energy actually consumed; or a measure of relative energy consumed to provide the same energy service.

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Why not use condensate from a split-unit air conditioner to improve cooling efficiency?

This is bugging me to the point that it almost enrages me. A split-unit air conditioner would typically cause condensate to form in the indoor unit. This water can be simply drained with gravity ...
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4 votes
2 answers
88 views

Is it more energy efficient to ventilate a home with an HRV/ERV or “shock-ventilation”?

In a reasonably cold climate like Hamburg, Germany where the standard practice is to open all your windows in the winter for up to 20 minutes once a day to ventilate your home (Stoßlüften or “shock-...
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1 vote
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Is PEX piping more energy efficient than copper?

My house has two bathrooms, with roughly the same distance of pipe from the water heater to each (see diagram below). One was added during a renovation and has PEX piping from the point where they ...
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Meta-campaigns for sustainable building management?

(Sorry if this is the wrong place to ask this. I considered politics--maybe that is better.) I have seen various groups that try to set up small campaigns targeted at individual organizations to ...
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Do solar panels generate more electricity in hot or cold climate?

Do solar panels generate more electricity in hot or cold climate? Who is right (sorry for the messiness, I currently don't know how to take a long screenshot)?
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4 votes
0 answers
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Radiative Cooling for Residential

I've seen a lot of references to films which radiate heat from an underlying surface out into space. For example: http://radi-cool.com/ https://arpa-e.energy.gov/technologies/projects/passive-...
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2 votes
1 answer
261 views

Renewables vs Fossil Fuel Cost Comparisons, without Subsidies

They said that Solar and Wind are now cheaper than fossil fuels. One of the primary reasons is subsidies and new technologies. Does anyone know the comparison research using No Subsidies. If we ...
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1 vote
2 answers
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Why is the Energy Guide efficiency rating of my air conditioner so much lower than the specification?

Now that my partner and I are working from home indefinitely, we decided to install central air conditioning. We got quotes for a unit with a 17 SEER efficiency rating, and ultimately picked this one. ...
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What type of solar panels to use for a house of 50 m2 and 3000 kW of consumption?

I am beginning to acquire knowledge to assemble my first self-consumption solar kit and I have been investigating what kind of solar panels I should use for a house of approximately 50 m2 with a ...
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6 votes
3 answers
616 views

Do SSDs have a lower environmental impact compared to HDDs?

In this question on Super User they say that Solid-State Drives (SSDs) use much less power than traditional Hard Disk Drives (HDDs). I read some internet posts and research articles that backup this ...
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How to ensure you are using efficient chargers for cell phones, laptop computers, and other electronic devices?

I recently asked a question regarding a sustainable way to generate white noise. I received a wonderfully helpful comment from Móż (thank you!) in which Móż recommended ensuring that the power source ...
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6 votes
3 answers
156 views

Is human energy efficient?

I spent 2 weeks traveling on my bicycle, and usually I was very hungry.. Since I ate a lot of food, I asked to myself if maybe a train (dividing cost between all passenger) was more green than me! I ...
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2 votes
3 answers
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How feasible is a city with no cars and no streets?

Saudi prince, Mohammand bin Salman, announced a future city spread in 170km with no cars and no street. But any place to meet daily needs like schools, medicine and office will not take more than 5 ...
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3 votes
1 answer
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Efficiently freezing an ice pack once per 48 hours

Question: What are some good electricity-efficient ways to cool an ice pack down to ~5 degrees C once every 48 hours? Background: I am in a warm climate and connected to the grid in a US city. I don't ...
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1 vote
2 answers
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Will this work to prevent my pipes from freezing?

I live in an apartment in the US midwest, and during the winter my pipes freeze unless I trickle my faucet. I think that the point at which it freezes is in a difficult-to-access exterior wall on the ...
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How much coil do I need to heat a given length of pipe (as a function of x,y,z)?

I'm imagining heating some water pipes using heating coils similar to these. Under various conditions, would I need to apply almost continuous lengths of heating coil to the entire length of pipe? Or ...
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1 answer
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Help me safely mod my freezer

I want to connect my freezer to an external thermostat like this to maintain a higher temperature than it otherwise could. Are there any thermostats or other control devices that would keep the ...
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1 vote
1 answer
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Why do the best energy star freezers have higher capacity and lower rated power consumption than the best refrigerators?

The title says it all; I'm looking for any qualitative information that can help me. Freezers: https://www.energystar.gov/productfinder/product/certified-residential-freezers/details/2255167 ...
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2 votes
1 answer
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Can I insulate my refrigerator to improve efficiency?

Any "reasonable" methods would be appreciated. I have heard that this can be done but I'm dubious that it would do much. Maybe if I put polyethylene on the right bits?
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1 vote
3 answers
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Keep my hands warm while working on a laptop?

I want to keep my hands warm(er) while working on a laptop in a cold room. Would it make sense to take a polar fleece blanket, fold it in half, sew together the two edges that are perpendicular to the ...
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3 votes
1 answer
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How to keep my tankless water heater safe in a cold room?

I have a room in my apartment that can sometimes get around 40°F (4°C), and that's where my new tankless water heater is stored. Should I take any special precautions to keep my pipes from freezing or ...
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2 votes
1 answer
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Most energy-efficient way to keep my pipes from freezing without tearing up walls/floor?

I live in a second-floor apartment in the US Midwest. For a few weeks per year, I have found that I need to turn on the baseboard heater in my kitchen in order to prevent the pipes in the kitchen and ...
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3 votes
1 answer
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Most efficient cheap heating system for small apartment in the US midwest?

I live in the US Midwest and am looking to upgrade from my current old baseboard heaters to a more energy-efficient solution. Any ideas? I am already well advanced on a parallel project of home ...
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2 votes
0 answers
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Help me estimate my annual refrigerator power consumption from this data sheet?

I am shopping for refrigerators and looking at this model. Feel free to let me know if that's stupid. But my main question is this: I'm trying to come up with a moderately conservative power ...
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2 votes
1 answer
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How does the EPA estimate annual power consumption for refrigerators?

I'm trying to get a simplified idea of how the EPA estimates annual power consumption for refrigerators, e.g. here. There are a number of reasons why I want to know this, but there are three big ones: ...
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1 answer
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How do I find an efficient AC-DC converter for low-power applications?

My understanding is that AC-to-DC converters each have their own "sweet spot" in which they achieve their rated or advertised maximum efficiency. I want something with maximum efficiency at ...
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2 votes
1 answer
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Should I turn off my Gas Water Heater if I will be gone for 3 days?

I have a gas water heater. If I go out of town for a week during warm months, I've been told that I will save energy if I turn the heater off before I leave. Would that still be true if I was going to ...
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2 votes
1 answer
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How to test accuracy of my Kill-A-Watt or similar device?

I have a used Kill-A-Watt power meter and want to see how accurate it is. In my "conventional" middle-class USA apartment, am I likely to have any electricity-consuming devices that I could ...
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1 vote
1 answer
161 views

Can I use a "normal" thermometer in a refrigerator?

My refrigerator has a rheostat that I want to turn up to save energy. I'm trying to figure out whether I need to get a dedicated refrigerator thermometer. I have a digital and a mercury-based ...
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5 votes
1 answer
49 views

What will happen if I leave my freezer off most of the time?

I only use my freezer to freeze ice packs, which I only use about an hour every two days. Because of this, I plan to turn my freezer off (or to the hottest setting) most of the time, and then reduce ...
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2 votes
2 answers
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How to get a small volume of freezer capacity with high efficiency and low cost?

I have a big refrigerator/freezer and barely use any of the space. I also don't necessarily need to keep things cold all the time, as I mostly use it to freeze ice packs and extend the freshness of ...
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2 votes
2 answers
2k views

What is the most efficient setting on my oil-filled radiator?

I have an oil-filled radiator with three heat intensities: Low (900W) Medium (1100W) High (2000W) Given the radiator has a thermostat, what is the most efficient heat setting to use? My goal is to ...
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3 votes
2 answers
672 views

How much more efficient is boiling water with a lid?

I sometimes end up boiling water in a pot without putting a lid on top because I can't find the lid. How much energy is wasted when bringing water to a boil without in a pot without a lid? Or ...
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2 votes
2 answers
144 views

Lowest energy use per passenger-km, electric bicycle or electric unicycle?

Which uses less electrical energy per passenger-km (pkm) travelled? Electric bicycle (with a single rider) Electric unicycle (aka. self-balancing personal transporter) I have heard that a standard ...
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2 votes
3 answers
89 views

How can I conserve energy and water in my bathroom? [closed]

I am interested in energy conservation and would like some simple tips on ways I can reduce my water and energy use in the bathroom in particular, as I feel that this is the place that I use the most ...
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5 votes
2 answers
150 views

Biomass: Digestor/Reactor vs Gasifier Efficiency

When using biomass for energy, two popular options are reactors and gasifiers. The first uses anaerobic micro organisms to convert the biomass to fertilizer and a methane rich gas mixture. The second ...
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3 votes
1 answer
50 views

Why is there no energy star certification for portable or box fans?

Why are there no energy star certifications for portable fans? From what I understand no portable electric heaters have the certification because using a portable heater is not efficient at all. ...
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0 votes
1 answer
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Is there any case where plant farming is more eco friendly than raising livestock?

I am looking for an example or a case with arguments that would justify converting cattle ranches into plant farms (e.g., wheat, apple, or anything non-meat). The advantages should be in a more ...
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4 votes
1 answer
61 views

Is this discrepancy between energy label and measured values reasonable?

My fridge is a Haier A3FE835CGJE and is rated A+++ (Europe, 2017), with about 200 litres volume, half of which for the freezer. It is a "no frost" model which does not require defrosting. The ...
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4 votes
3 answers
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How to reduce energy usage of a window air conditioner?

In the summer, we use a window air conditioner in our bedroom to be able to sleep comfortably at night. It takes a while to cool, and I know it uses quite a bit of energy. Here are a few steps we take ...
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3 votes
1 answer
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Costs of transportation

I assume that it makes sense to ask for the energy costs of transportation of different goods per weight and volumetric mass density, depending on the means of transportation (truck, train, ship, etc.)...
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3 votes
1 answer
71 views

Is an air to water heat pump appropriate to keep a hot tub at temperature throughout the year?

Is an air to water heat pump appropriate to keep a hot tub at temperature throughout the year? The hot tub will run 24 hours a day, seven days a week, covered when not in use. Presumably if the ...
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0 votes
2 answers
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What level of light intensity (lumens) do you need across a solar panel in order to obtain 15% energy efficiency?

What level of light intensity (lumens) do you need across a solar panel in order to obtain an incident-light to energy-output efficiency of 15%?
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0 votes
2 answers
170 views

Is hydrogen a good way of storing energy from excess hydroelectric generation? [closed]

Referring to hydro electricity generation, a lot of what we produce is wasted as the buyer buys only the minimum generation. What would be the appropriate measure to use that excess energy? Is ...
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4 votes
2 answers
72 views

Does air duct cleaning increase heating efficiency?

I recently moved into an older house with a natural gas-burning forced hot air furnace. There are no records of the ducts being cleaned, and based on the layer of black grime I can see, they are quite ...
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4 votes
2 answers
532 views

How to choose between an electric, natural gas, or heat pump clothes dryer?

I will soon be moving into a new home with a very old electric clothes dryer. I expect that before too long it will fail and need replacing. I would like to replace this with a more efficient model. I ...
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2 votes
3 answers
276 views

For overnight heating, is it more efficient to use an electric space heater in a bedroom or a whole house natural gas furnace?

Is it more efficient to heat a bedroom with whole house's forced-air natural-gas burning furnace, or only an electric space heater in the bedroom? For a very location-specific application, electric ...
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4 votes
1 answer
199 views

Are crypto currencies sustainable?

Except generating a different kind of "money value", what is the sustainable value of crypto currencies compared to the energy consumed to generate them? Compared to currencies working with ...
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15 votes
1 answer
215 views

Does transporting plastic offset the benefits of recycling it?

Apparently China has been processing about half the world's waste until this year, and most of that waste is transported over the ocean in large container ships. Recycling plastic uses less energy and ...
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4 votes
1 answer
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Are all Peltier-type stove fans the same?

I'm considering a stove fan to distribute heat from a small wood burner. The prices of commercial Peltier-type stove fans seem to range from £25 to £100. Is there likely to be a significant ...
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