I live very close to the the geographic center of the US and have a 6.5KW system attached to a 6KW grid tie inverter. I have a gas furnace and water heater. Over the last winter (read heating season) I produced about 1200 kwh's that I didn't use and sold back to my utility company at an astonishingly low $0.015 per KWH (my utility won't pay me retail for pushing power back onto the grid, only the "saved fuel cost"). I figure that if I would have used these same 1200 kwh's to power a 1500w electric space heater properly positioned in my house for a few carefully chosen hours a day, it would have offset a little more than 6,000,000 BTU's of heating over the course of the winter, which would have lowered my monthly natural gas bill substantially more than the $18 I got paid for my excess production. So I'd say it's not a fools errand to try to do this if you find yourself overproducing in the winter in some cases, depending on how your utility handles net metering.
Using excess solar to heat house
- Thread starter Aussie_Pete
- Start date
efficientPV
Solar Addict
- Joined
- Sep 24, 2019
- Messages
- 1,341
Everyone likes to spend OPM (other peoples money). Resistive heating is an ultra cheap investment and can have very fast response times to gather moments of power. Here is just a half hour of my diversion in cloudy conditions.
Half an hour heats up my living room, and that with less than 1500W.
Sure, an electric heater is easier to control. And cheaper to buy. But I doubt if it really is cheaper.
With 1000 kWh you can generate roughly 5000kWh of heat, making huge savings on the gas bill. And if you don't have excess solar power, it probably runs a lot cheaper than the gas unit.
Sure, an electric heater is easier to control. And cheaper to buy. But I doubt if it really is cheaper.
With 1000 kWh you can generate roughly 5000kWh of heat, making huge savings on the gas bill. And if you don't have excess solar power, it probably runs a lot cheaper than the gas unit.
Ampster
Renewable Energy Hobbyist
I don't have excess solar because I am grid tied. I do heat my home with electricity. I chose to use an air source heat pump for heating because it is more efficient than resistive heat and my solar generation in the winter drops off.
Zwy
Solar Wizard
It wasn't save $18, it was $18 the power company paid for the excess.
Nothing wrong with what the member is doing, it's cheap and effective. A air to air mini split doesn't work in all climates. Take for instance my area where it isn't uncommon to see -30F for a few weeks in the winter. The mini split wouldn't do me any good in the temps colder than 20F, regardless of what some manufacturers may claim. Efficiency suffers greatly due to defrost cycle and you don't exchange a large amount of btu's per watt used. One could install a ground source heat pump but that would probably require additional PV and batteries to run it, plus it won't be a cheap installation.
Zwy
Solar Wizard
Yes, everyone has unlimited money according to some. I've lived with no money, some money and plenty of money. But I don't spend it based upon someone's opinion about what I "should" do.
Yes, lets find all the right circumstances to not make this work. Boy, can you think anymore in problems than in solutions?
I don't know what everybody here is wining about "spending other peoples money"
I just suggested a way to use excess power in winter more effectively, in a way that even reduces your gas bill in moments you don't have excess energy. I merely suggested to calculate the difference, and see if it comes out better.
If the answer is no, because of the climate, or because he doesn't have the money anymore, then that is fine.
By the way, I only heat my house with an airconditioning system that works up to -5F. Yes it would not do for all climates. But then there are Nordic models that go up to -30F. And probably -5F is sufficient to use excess solar power.
For our climate, the -5F limit is great, it means I can always heat my house with it.
The Coefficient of Performance indeed is getting lower, the colder it gets. But for example at 20 degrees Fahrenheit, it still produces 3 times more heat than the cheap electric heater!
And since natural gas prices are on the rise, it could be very worthwhile
efficientPV
Solar Addict
- Joined
- Sep 24, 2019
- Messages
- 1,341
My math may be wrong, but $18 at grid fuel costs looks like 310KWH excess for the year exported. At grid rates it is less than $50. It doesn't seem like you should invest in more than a space heater to utilize that.
He clearly states 1200kWh excess to the grid.
1200kWh with a coefficient of 4 to 5 means over 5000kWh thermal energy with a heat pump.
5000kWh thermal energy is the same as 500 cubic meters of natural gas, which should be the same as 17.500 cubic feet natural gas if my conversion to imperial sizes is correct.
Might be worthwile to lower the gas bill.
Zwy
Solar Wizard
If you so desire, I'm certain I can find many more.
The problem with any air source heat pump is efficiency starts falling off below 20F. Moisture will condense on the outside coil and either a gas defrost event has to occur or (gasp) a heating coil heats the coil. Both take energy. Most air source heat pumps are rated/tested under optimal conditions, even digging thru all the specs for most won't reveal the actual coefficient rating under suboptimal conditions.
I'm not against inverter heat pumps, they certainly have a place in any solar system. I plan on using one or two in my house for cooling, plus heating when outside temps enable efficient operation such as late spring/early fall.
It's always easier to spend someone else's money. I've been in business for 35 years and spend other people's money for them all the time.
timselectric
If I can do it, you can do it.
- Joined
- Feb 5, 2022
- Messages
- 18,419
Again.......
If it's excess power, that would otherwise be wasted.
Who cares if it's used in the most efficient way.
If it's excess power, that would otherwise be wasted.
Who cares if it's used in the most efficient way.
Zwy
Solar Wizard
At $.20Kwh, $240/year.
He must only get $0.015 per Kwh from the utility.
1200Kwh = 116.8 cubic meters= 4124.75ft3h
Convert Kilowatt Hour (kW*h, Common Units) to Normal Cubic Meter Of Natural Gas (Natural Gas Energy Equivalent)
Online conversion from Kilowatt Hour (kW*h, Common Units) to Normal Cubic Meter Of Natural Gas (Natural Gas Energy Equivalent). Energy Converter.
$15 per thousand cubic feet
4.12475 x $15= $61.87
@Zwy You should do the 1200kWh (electrical) multiplied by the coëfficiënt of performance of the heat pump system (typically close to 5, not on the coldest days) and so the 61 dollar can be multiplied with that as well.
So you save over 250 dollar each year, and you might get more savings because the system might be cheaper to run than the gas system.
But your gas prices are very low, so the earnings are a bit less there.
Anyway, it looks like there is a difference of 200 dollar each year between using a 20 dollar resistive heater or a small AC system.
So you save over 250 dollar each year, and you might get more savings because the system might be cheaper to run than the gas system.
But your gas prices are very low, so the earnings are a bit less there.
Anyway, it looks like there is a difference of 200 dollar each year between using a 20 dollar resistive heater or a small AC system.
By the way, yes air source heat pump systems can go into a defrost, reducing the efficiency at that point. However, it is dependend on many factors.
And more important, overal system efficiency is still worthwhile in many places, meaning that it is cheaper to run than heating with natural gas. Perhaps not for your case.
Keep in mind that they use heat pumps in Scandinavia too, the real cold doesnt have to be an issue.
And more important, overal system efficiency is still worthwhile in many places, meaning that it is cheaper to run than heating with natural gas. Perhaps not for your case.
Keep in mind that they use heat pumps in Scandinavia too, the real cold doesnt have to be an issue.
Zwy
Solar Wizard
I don't disagree there but that would depend on the COP of the unit. You have to have the base cost in gas in order to determine if it was cost effective. Cheaper units run a COP of 3, so it could be $180/year or a COP of 5 and $300/year. Of course the purchase price is higher as COP goes up.
I just used the price I could find in the internet, it's probably closer to wholesale than retail. I don't have natural gas here, LP gas is what I burn.
It's somewhere in that area. 15 to 20 year lifespan on a unit, $3000 to $4000 that is overall reduction over cost of gas but doesn't account for initial purchase of unit and installation plus interest if the cost is financed. Depending on the unit and skill of the person, it may not actually pay out that well based upon today's energy cost. However, one needs to take into account the air conditioning aspect and the cost reduction of using an inverter mini split compared to a central cooling unit or older window air conditioner. The air conditioning usage alone usually pays back on the unit fairly quickly. That is my main purpose for installation.
copec
Solar Enthusiast
- Joined
- Jan 23, 2021
- Messages
- 335
What app am I looking at?
notarichman
New Member
- Joined
- Feb 20, 2022
- Messages
- 102
how about plugging in a space heater to your inverter? i bought a couple of 350w space heaters with fans and i can use them to keep from turning on my base board heater...thus saving the power that the b.b. heater uses. most space heaters are 1500w. you could pick which heaters your system can support and keep your batteries charged.Hello all from a solar & battery newbie,
I'm currently getting a 5.2kwp solar PV system and linked 7.2kwh battery on my house in Scotland. I've been researching for about 6 months and the system is due to be installed this month.
I've been looking at what technologies are out there to exploit excess solar once the batteries are charged. I'm aware of heating water using an Eddi or I-boost, charging an EV using a zappi, but was wondering if anyone had considered installing an electric flow boiler (like the one linked below) on their existing central heating system, driven by excess solar to reduce cost of central heating? It seems to be a relatively new technology, but when integrated with solar could significantly reduce gas or oil use for central heating.
For clarity, I’d be considering installing in addition to the existing oil or gas boiler, so that when there’s excess solar this would heat central heating and when there’s not solar the gas or oil boiler would run heating
Slimjim Electric Flow Boiler | @electricheatingcompany
The SlimJim is traditionally installed in properties such as apartments, domestic dwellings, holiday homes & light commercial properties with limited spacewww.electric-heatingcompany.co.uk
efficientPV
Solar Addict
- Joined
- Sep 24, 2019
- Messages
- 1,341
That is E-test for use with Atorch/Hidance AC or DC power meters. It has some features that almost make it useful, but ok for a $13 100A 300V power meter. Sorry, not an app for diversion.
A lot of beer talk about what to do with excess solar. Not much at all about how to control it. Even mini splits with inverter drive have a limited range to dump power. Just how does the general public control speed and temperature? Is iton most of the tome and utility power is just blended making it 1/3 or 1/2 utility power cost. Any effective diversion would have to have some resistance element to it to capture over and under dump levels. Phase triggered diversions like the eddi can do that. Electronics is my field and I still consider diversion to a heat pump as quite a task. I don't know what average solar enthusiast would do to accomplish this. Most decisions would have technical flaws which would waste some power.
Don't bother, your panel won't produce anything if it can't be used or store, so, there is no waste of energy at all, it is just your perception at work . And you know what, that's good for your inverter to not try to convert at full rated for nothing .
That being said, some inverter (like DEYE ;-)) can handle what they call a smart load, basically you can instruct your inverter, on some situation (battery threshold and load threshold) to power a heater (or any resistive load) . So you can say turn on the heater as long as battery is 80% charged and house load is under 20% max capacity for a fix duration or not..
its enought for me to heat water, I don't have winter. there'are so many thing you can do before starting to heat your house with solar panel ;-). In fact it should be the last thing to do.
. And you know what, that's good for your inverter to not try to convert at full rated for nothing .That being said, some inverter (like DEYE ;-)) can handle what they call a smart load, basically you can instruct your inverter, on some situation (battery threshold and load threshold) to power a heater (or any resistive load) . So you can say turn on the heater as long as battery is 80% charged and house load is under 20% max capacity for a fix duration or not..
its enought for me to heat water, I don't have winter. there'are so many thing you can do before starting to heat your house with solar panel ;-). In fact it should be the last thing to do.
