replacing CFLs with LEDs

...supposedly, 3-year warranty, but I personally would wonder more about the "life-time" of that built-in fan.

 

You obviously have more faith in such fans than I do. In my prior work, such mechanical devices had a finite life-span which shortened with both vibration and heat proximity...as appears in their illustration. And, obviously, when the *unservicable* fan goes, the whole LED assembly becomes a throw-away device, without any expectation of "repair/replacement."

 

"Trumpet...ing" due to motor sitting at bottom of a coronet-shaped light fixture?

 

Good 42" TVs are a lot less than $500. Go to slickdeals.com and set up an alert for 'LED TV'
I recently bought a 55" TCL for $500 shipped that I am very happy with.
The old TV was not mine to dispose of, but I did recoup $50 on the digital to analog converter box that was no longer needed, and I save its power draw.

For power draw, divide the annual Wh by 1825
E.g. 64 kWh annual is 64000/1825 = 35 watts (over a year used 5 hours a day)

---
For cost savings I would first figure out my power savings per device, and say over a week figure out how many hours a day it is on.

So, e.g,
Device #1: old watts 300, new 80; 5 hours a day
Device #2: old watts 200, new 100; 4 hours a day

Then I know that I am saving 220*5 + 100*4 Wh a day.

 

Most of the heat released by a light bulb itself is radiant, not convective. Most heat-lamps shine downward. Heat is generated on the surfaces which absorb the radiant heat, and some of that heat is transferred to the surrounding air which is convected upwards. The rest is reflected the other direction, where it strikes something else, and is re-radiated until all of it is eventually absorbed.

All electric lights produce heat; which is basically the difference between luminous efficiency and 100%. For example, if an incandescent light is 2% efficient, 98% of the energy is converted to heat. An LED light may be 15% efficient, therefore 85% is wasted as heat.

One thing to remember is that all electric heaters are 100% efficient, despite claims that some types are more efficient than others. Here is an example:

I've seen these damned things advertised for more than 20 years as "more efficient" than other electric heaters, a claim which defies basic physics BTW. Originally they were sold on TV for over $800. then in hardware stores for $400, then discount stores for $100. I saw this one on Ebay for $18. Still more expensive than a basic electric heater. There must be a lot of these things to get rid of.

 

Gee I think any LCD TV is OK.
The way I look at it, in the winter I am happy my TV makes some heat because fam room is too cold.

 

All electric heat is 100% efficient...that is if you are referring to resistance electric heat. Heat pumps can BR significantly more that 100% EF depending on design, Delta T etc. A ground source Heat pump can be 125-200% efficient. That is for every BTU used to power the system it can deliver 1.5-2 BTUs to the room. The mini split air source heat pumps are very EF and very reasonably priced. You can even do a DYI install with out having to p urge and charge.

Icarus

 

Not exactly. Electric efficiency calculations shouldn't count the wire losses outside the desired heating space (back at least to the meter, if not farther) any more than combustion heat appliances should be allowed to count the heat dumped out the chimney exhaust.

But otherwise, the statement is reasonably close to reality. In a properly wired building, any of them will be close to 100%.

The manufacturer's site doesn't appear to claim greater efficiency than other electrics. Re-sellers are a different matter.

And if it provides a spot or zone heating boost that allows a central heat system to be turned down, then it can be "more efficient".

An Energy Star ground source heat pump must be at least 310% - 410% efficient on a certain test, depending on type (open- or closed-loop, water-to-water or -air, etc.)

 

^thanks for the heat pump numbers.

I don't think line loss outside the building envelope would be enough to change the basic calc. The real issue with electric heat is it takes way more energy at the generating station (plus cumulative line losses) that the appliance generates. Something in my memory says it takes 2 BTUs to get one in the envelope.

Icarus

 

Yes, line loss isn't enough to change the basic calculation, but is just enough to set aside the common 100% efficiency claim. At full production power, my solar system is losing 1.3% just in long wire losses from the PV modules to service meter, not counting extra losses at joints and switch contacts. Many electric heaters in home use will see 1 to 2% in similar losses (for 240V heaters, double that for 120v), depending on the wire run length.

For other losses, I'm seeing claims that electric distribution system losses are typically 8-15%, or just 6%. A government spreadsheet shows estimated losses near 7% in 1996, dropping closer to 5% in 2012.

The power plant efficiencies vary sharply by type. I seem to remember big old thermal plants, coal and nukes, being in the low 30% range. Newer coal plants should be better, but still well below the 60%-ish of the best combined cycle natural gas systems. Big hydro plants should be in the 90%-ish range, so reaching 95%.

Note that with these numbers, the best natural gas electric plants driving the best heat pumps should provide well over twice as much residential heat as the best possible natural gas furnace.

 

Thanks,

That said, I love my 95.6% natural gas combi boiler!

Icarus

 

I agree with the sentiment but my numbers come out different:

1. A condensing home furnace burning NG has an EF of about 90%
2. A central NG electric plant might get up to 60% thermo efficiency, and then has ~ 6% line losses and the electricity is consumed in a heat pump that in a cold environment brings in 1.5 - 2.0 heating units for every one consumed. That works out to a range of 1.5*0.6*0.94 to 2.0*0.6*0.94, or 84.6 - 112.8%

The real issue is that very few households can connect to a grid that has an average thermo efficiency of 60%. Mini-duct+PV+tight_house is much more to my liking, with the grid for back-up.

 

The 1.5 - 2.0 factors should be for an air-source system (with R134a or R410 working fluids) in a particularly cold climate. For a climate more closely approximating the HSPF seasonal profile, an Energy Star air source heat pump must bring in at least 2.3* heating units (single package system) or 2.4* units (split system). My mini-split, six years old, is rated 2.9*. Better units were available then, and better still now.

R744 systems should degrade much less in colder climates, though I have no idea when they'll become readily available.

Energy Star ground-source systems have higher minimum ratings of 3.1 to 4.1 heating units per unit consumed, though operate in different conditions, e.g. warmer heat source.

* I'm converting HPSF units to equivalent COP, and hope I'm doing it right:
HSPF 8.0 = 2.34
HSPF 8.2 = 2.40
HSPF 10 = 2.93
HSPF 11 = 3.22

 

^^ Thanks

I'd be wary of the Energy Star specs. Not only are the temperatures relatively high, I gather that the unit is operated in its most favorable condition. New England type real world reports I keep reading are 2.0 or less.

 

Where does the energy from wire losses go? Heat. That's close enough to 100% for me. Even the energy that runs the fan ends up as heat in the room. Same for the faint amber glow glow of light from the quartz tubes; the light is absorbed as heat. If 100% of the electricity being pulled by an electric heater doesn't end up heating the room, I'd like to know where else it goes.

I don't count wire losses behind the meter, because I don't pay for it (at least not directly).