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I oversized my system since I'm getting an EV in a year a half, (I use 4,000 kWh year system will produce 6,550 kWh year) any recommendations on electric space heaters so I don't have to use the gas to heat the house?
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Only one: Don't.
If you do, and nat. gas is available, you'll be doing a very foolish thing. The fuel cost of providing the same heating value using electric resistance heating is usually close to 3X that of the cost of natural gas, and probably close to 2X that of propane. Even considering a rather archaic .70 combustion efficiency, gas wins hands down. What are you thinking (or smoking) ? -
If you have some KWH to burn before a true up date, an electric heater could use it. The first thing I'd worry about
is safety. I have seen too many plug in circuits heat up and literally blow up when pushed continuously. A heater
should be installed and hard wired, for example like an electric fireplace. Mine has an ugly piece of conduit going
into it. And a proper thermostat. Those I have are not located close to anything that can burn.
Natural gas will be the cheapest heat, but not doable for all. Besides a very expensive line installation here, the
connect fee would be around $400 a year before even using any gas. It was only a few dozen $ in recent times,
I wonder what it will be in the future?
Propane has been $1 a gallon here in summer, but artificially inflated to $5.25 in the worst of winter. That rate is
double electric resistance heat. A good heat pump can multiply your KWH by maybe 3, making it quite competitive
with propane. But most air to air pumps lose effectiveness much below freezing. A decent heat pump covers 90%
of my needs here in northern IL; the rest is either electrical resistance or propane. Bruce Roe
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I ended up getting DeLonghi HMP1500 Mica Panel Heater on amazon for $69, my kill-o-watt shows 730 watt. I'm thinking using my gas fireplace in the front room during the day and my mica panel heater in the bedroom at tight, it's going to be an interesting experiment. I figure if I can recoup the cost of the panel heater I can save face from @JPM.
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Unbelievable. The Brightness knob does not work on the monitor.Last edited by Sunking; 10-27-2016, 07:14 PM.MSEE, PEComment
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I used a space heater for a while, and its energy consumption was off the charts. Probably want to avoid them.
A couple other ideas:
Have you priced a heat pump? There might be some affordable minisplit heat pumps or even portable heat pumps that would help, and would still be useful even after you get that EV.
Is your water heater gas-fired? If so, how old is it? If it's nearing the end of its life, you could consider replacing it with a heat pump water heater. (Caution, check the reviews, early units had some problems; also be aware they may need a drain and more space than regular water heaters, and make more noise.) I'm itching to do that myself once things settle down a bit around the house.Comment
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The heat pump is a cool idea, I saw this Pioneer Air Conditioner Inverter+ Ductless Wall Mount Mini Split System Air Conditioner & Heat Pump Full Set, 9000 BTU 115V on Amazon for $696, but since my house was brand new from 2010 I'll hold off on that.
My water heater is natural gas, from the beginning of 2010. I saw this Rheem
Performance Platinum 50 Gal. High Efficiency 12-Year Warranty Hybrid Electric Water Heater with Mobile Alerts on at the home depot but it's $1200 and I don't see any good reviews on amazon and I read you should not install where it's cold and my current water heater is in the garage.
What do you think of Ecosmart ECO 18 Electric Tankless Water Heater, 18 KW at 240 Volts $387 on Amazon really popular and easy install and the Takagi T-KJr2-IN-NG Indoor Tankless Water Heater, Natural Gas $534 also on Amazon? I'm only concerned of the operation cost.
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Here is a company that may provide the product you are looking for.
I have two of these units in my house...... I charge them up when the sun shines and discharge the heat when I need it. It works for me. Sometimes the "experts" do not know what they are talking about. You have to know your cost of production to make good economic decisions. What does a Kwh cost you and how does it compare on a BTU basis with other forms of energy? Some of the experts here have no clue. Just saying..........Comment
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2500kwh is not a lot of excess kwh to use.
Unless you live in a very mild climate you're probably going to still need to use gas.
I've used an oil filled electric radiator for heat in a basement - it was a dusty env. and that minimized risk of fire.
And I've used an electric radiant heater - red-hot element that if you dropped a blanket or piece of paper onto it it would probably catch fire. (That one I was very careful of and concerned about fire)
And in my dorm room many years ago I had a little ceramic heater with a built-in fan.
Hard to say what would work well for you (and not cost as much as what you save in natural gas)
I would expect that whatever you do it'll only supplement your normal heat - decrease your cost by allowing the furnace to run less often (possibly more than you'd see from just kwh vs. btu. Because you can turn down the heat for the house and warm up just the room you're in.)Last edited by foo1bar; 10-27-2016, 06:44 PM.Comment
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That site is EXTREMELY vague; no numbers or even description of type of energy in and out.Here is a company that may provide the product you are looking for.
I have two of these units in my house...... I charge them up when the sun shines and discharge the heat when I need it. It works for me. Sometimes the "experts" do not know what they are talking about. You have to know your cost of production to make good economic decisions. What does a Kwh cost you and how does it compare on a BTU basis with other forms of energy? Some of the experts here have no clue. Just saying..........
Here is my attempt to put real numbers on conversions and equivalents. The most important
one for me: my 27 megawatt hours of PV energy a year (resistance) equal about 1050 gallons
of propane (95% furnace). Bruce Roe
With gallons or cu ft of oil or propane or nat gas; BTU, Joules, KW, KWH, THERMs, TONs, SEER, EER, & COP, I needed a table of formulas to directly compare things. My own preference is to reference everything to KW or KWH. Exact conversion ratios subject to a bit of international fine tuning. Also the exact units (KW DOES NOT = KWH) help avoid confusion, and failure to cancel properly indicates error. First things are divided into TOTAL ENERGY or ENERGY FLOW, and some industry comparison factors. Keeping in mind, ENERGY FLOW X time = TOTAL ENERGY.
____________________________________________
TOTAL ENERGY 1 Barrel of OIL = 500 lb OIL = 58.095 THERMs
1 gallon PROPANE = 91,690 BTU = 26.8717 KWH
1 cubic foot NATURAL GAS (US) = 1028 BTU = .301277 KWH
1000 BTU = 1,055,000 JOULEs = 0.293071 KWH
1 THERM = 100,000 BTU = 29.3071 KWH
1 JOULE = 1 WATT SECOND
1 KWH = 3,600,000 JOULES = 3412.142 BTU
++++++++++++++++++++++++++++++++++++++++++++++++++ +++
ENERGY FLOW 1 Watt = 3.412142 Btu / hour = 1 JOULE / second = 3600 JOULEs / HOUR
1 TON = 12,000 BTU / HOUR
++++++++++++++++++++++++++++++++++++++++++++++++++ ++++
ENERGY COMPARISON FACTORS SEASONAL ENERGY EFFICIENCY RATIO (seasonal overall) air conditioner BTU / hour divided by SEER number = W consumed
from a scientific notation view, the SEER has units of BTU / WATT
EER = 3.41214 × COP
EER is more realistic, typically 7/8 of SEER for residential cooling
from a scientific notation view, the EER has units of BTU / WATT
COP heat pump Coefficient Of Performance
cop is the RATIO of (heat) energy delivered to energy consumed.
for BTU & KWH units, it may be calculated by
COP = (capacity in "BTU" / electrical power in "KWH" ) / (3,412.142 BTU / 1 KWH)
from a scientific notation view, the COP has no unitsLast edited by bcroe; 10-27-2016, 11:07 PM.Comment
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FWIW, 1 kWh of electricity has the equivalent heating value of 3,412 BTU or so. Period. That electrical energy can be used for resistance heating, which will get you 3,412 BTU of heat.Here is a company that may provide the product you are looking for.
I have two of these units in my house...... I charge them up when the sun shines and discharge the heat when I need it. It works for me. Sometimes the "experts" do not know what they are talking about. You have to know your cost of production to make good economic decisions. What does a Kwh cost you and how does it compare on a BTU basis with other forms of energy? Some of the experts here have no clue. Just saying..........
Or, that 1 kWh of electrical energy can be used to power devices that "pump" heat from a lower energy level in one location (usually outside a dwelling) to a higher energy level (usually inside), with the desired result that more than 1 kWh (3,412 BTU) of thermal energy will usually be transported, often 3 or more times as much will be transported. The ratio of energy "transported" or "pumped" to the energy consumed in the process is called the Coefficient of Performance (C.O.P.) of a device called a heat pump.
The units DanS26 refers to are thermal storage devices that use electric resistance heating elements coupled to thermal mass. They've been around for a long time in one iteration or another. Because they use electric resistance heat, they are no more efficient than other electric resistance heaters - that is, their C.O.P. == 1.0 Think of them as big bricks heated by electric resistance elements embedded in them. Their big advantage is when used in conjunction with time variable POCO rates. Such units are switched on when electric rates are low, or I suppose if/when they can be coupled to some PV device. Such devices have a relatively large heat capacity that can be charged (heated up) when rates are low, and then that heat can be withdrawn from the unit, in this case with a blower, to provide heat when rates are high(er) The savings happen in a relative sense and are made possible by the time differential in POCO rates. On tiered rates there will likely be no savings, relative or otherwise.
Depending on how cold the climate is or the winter gets, there's a pretty good chance a quality heat pump may well be more cost effective than a Thermal Storage Device (T,S.D.) until temps. dip into the 20' (F.) or less.
Also, if such a T.S.D. is used, and the main heating source is some fossil fuel (nat. gas, or propane, or coal for that matter), I'd take care that the cost of the heat the T.S.D provides, even at off peak rates, is less than the cost of the fossil fuel with combustion (in)efficiencies accounted for. .
Grossly oversimplified example: Say I pay $ 8.00 per million BTU of nat. gas ( ~ 1,000 ft.^3). Also, I pay, an off peak rate of $0.12/kWk for POCO electricity. Also, the thermal efficiency of my furnace/boiler is 0.70. That means the cost of 1,000,000 BTU of delivered fossil fuel heat is ~ ($8.00)/.70 = $11.43.
The cost of an equivalent amount of heat supplied by resistance heat (at 100% efficiency) = (1,000,000) * ($0.12)//3,412 = $35.16.
The cost of nat. gas is less than $8.00/1,000 ft.^3 in many markets at this time, and the $0.12/kWh is about the national average. The 0.70 efficiency is on the low side these days, but not all equipment is new.
At $8.00/1,000 ft.^3 for gas, the competitive electricity cost would need to be ~~ $0.039/kWh. Maybe possible in some markets, but the price would need to be lower if the cost of the fossil fuel is less.
Use the above as you see fit, maybe a go by.Comment
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So the T.S.D. is electrical resistance input and moving air output? And how many BTU can it store? If the device involves a state
change I'd expect BTUs to be much larger, but with a more restricted temp range output. My feeling is its an overnight sized unit,
not much use for a week and none for seasonal. And has no contribution to make for a fixed rate grid tie system?
Seems like the T.D.S. ought to be available with a heat pump type input. That could be useful, where the efficiency of the
heat pump is much higher (or even possible) days, than nights. Bruce RoeComment
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Though as you say, the site being extremely vague, and considering the forced air configurations only for the time being, while other configurations are certainly possible, electric resistance input and convective output, with or without a heat pump seems to be where this mfg. has put their marbles. The T.S.D. site Dan S. referenced uses sensible heat storage - no phase change - These things use bricks. FWIW, phase change is, IMO, beyond the ability, resources or hassle tolerance for most homeowners.
How much heat the subject T.S.D. can store is f(mass, sp. heat of the material, temp. diff. thermal mass to dwelling amb. air temp.). Given the weight of the unit, and the sp. heat of the storage material of probably something like 0.20 - 0.24 BTU/lbm deg. F., the unit seems to be capable (or designed) for operation at quite an elevated temp.
I would agree that the subject units are designed for something like daily cycling.
If I understand what you are writing correctly, using a heat pump rather than resistance heating elements may be more complicated than appropriate here, but briefly, while a heat pump input rather than elec. res. is possible, it's unlikely. Temps. from a heat pump output to heat the storage medium would not be high enough to allow storage of more than ~ 10,000- 20,000 BTU depending on unit size. That, and the added initial cost of a heat pump over resistive elements would probably negate any possible savings from time shifting of loads.
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The mfg. does show what appears to be the T.S.D. as an adjunct to a heat pump output. I'd question the economics of that, but would need more input/study to get a better handle.Comment
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Here's what you guys are missing in your analysis.....with resistance heat that is localized to the room or space that you are located then these units are extremely efficient. You do not need to heat the entire house or a series of rooms....just the space you are in.
In my case a kWh cost me $.03 in the daylight hours when my solar system is producing excess kW. That equates to $8.82 per mBTU per broe calculations, which I agree. Propane at $.89 per gal is $10.89 mBTU. Bruce, you tell me which heat source you would use.
Don't just outright denigrate resistance heat......it all depends on what a kWh cost you and how much space you are heating.Last edited by DanS26; 11-04-2016, 08:15 PM.Comment
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I try to use my KWH reserve very efficiently, with a late model air-air heat pump
most of the year. When it gets too cold for the heat pump, I have about 9KW of
resistance heating available. In mid winter my propane price can go up by a
factor of 5, so I don't plan to use enough propane to need a winter refill. If there
was a power outage, I'd start the generator and run the propane furnace.
Basically when a gallon of propane costs more than 27 KWH, I or anyone can
resistance heat cheaper. That is, if they keep track and have the flex facilities
to switch in place.
I'm not putting down resistance heat, just recognizing it as my least efficient
source of heat. My PV system was sized from the beginning to cover substantial
resistance heating. So I can change with the situation, but I am no longer
controlled by the current price of energy. I don't know what my KWHs cost, but
I haven't bought one from the PoCo in 3 years.
I have played the "heat one room" game, the "turn down the heat and wear your
coat indoors" game, but I decided to try collecting enough of my own energy to
set the heat wherever I want. So far its working. Bruce RoeComment
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Makes sense to me. Also, I think the cost of different heater types need to be considered as part of total cost/benefit analysis. I understand heat pump is more efficient than resistance heater but what's the cost difference in terms of equipment and potentially electrical wiring changes required. I am in kind of similar situation as the OP except I didn't over produce but I have lots of NEM credit due TOU rate plan. So, my cost for electrical is essentially 0 within NEM credit limit and I plan to try portable safe electrical heaters to supplement natural gas central heating. My natural gas cost is much lower than electricity cost so I wouldn't do this if I didn't have NEM credit.Comment
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