switching to Electric from Natural Gas after big solar install in North East region

[doctorman]

With the price of solar falling rapidly I want to do a self install of 20KW system on the roof in New York.
New york region
3500 sqft house
7 people in the house
4 bath

we just bough this house and doing major renovation , major insulation enveloping the house and making it efficient
huge east west roof with no shade is begging for solar
a 20 KW system costs around 22KW in parts and around $32K installed plus the state and federal tax credits
probably another 10K in whole house foam insulation
we are changing all appliance, water heater, and central AC

in NY national Grid is around 40cents per Therm
PSEG Electric is 22cent per KW

the prices will go up yearly and increase my solar value

so ...
I am going with electric Hybrid water heater , Natural gas cook top, Electric oven
Question is how to heat the house
I know natural gas is the go to for everyone but I have not seen actual calculation on it

I am putting a 2 zone 2ton and a 4Ton heat pump for cooling 22-25 SEER
for heat I wanted to put a new tankless high efficiency boiler with coils in air duct to heat up the house
question is should I do natural gas on the boiler or electric
I was gonna go with dual fuel system for natural gas a s back up perhaps.

am I delusional or in denial?

at 20KW system at this price range I wouldn't mind selling the left over back to PSEG at 4-5 cents per KW (which might go up with inflation etc)

my goal is to leave comfortably in the house and not worry about paying for energy needed for the house.

Geothermal is not an option as the city code prohibits it.

[J.P.M.]

Use nat. gas to heat the dwelling, and for water heating as well. At $0.40/therm, you'll have a long payback in a conversion to electric of any sort. Besides, nat. gas heat is often more comfortable. Also, but who really knows, the price of nat. gas is expected to be stable for the reasonably foreseeable future.

Nat. gas is a bargain that solar can almost never compete with in terms of a source of heat. Do your homework on cost and what you get in terms of bang for your buck for nat. gas, electric heating and solar. If you do, you'll be better informed and better able to see through the hype that's abundant.

[ButchDeal]

Question is how to heat the house
I know natural gas is the go to for everyone but I have not seen actual calculation on it

I am putting a 2 zone 2ton and a 4Ton heat pump for cooling 22-25 SEER

So you are only going to use the heat pump to cool?

[doctorman]

So you are only going to use the heat pump to cool?

yes lennox xc25 system

[ButchDeal]

yes lennox xc25 system

that is not a heat pump. It is an air conditioner.

[doctorman]

Use nat. gas to heat the dwelling, and for water heating as well. At $0.40/therm, you'll have a long payback in a conversion to electric of any sort. Besides, nat. gas heat is often more comfortable. Also, but who really knows, the price of nat. gas is expected to be stable for the reasonably foreseeable future.

Nat. gas is a bargain that solar can almost never compete with in terms of a source of heat. Do your homework on cost and what you get in terms of bang for your buck for nat. gas, electric heating and solar. If you do, you'll be better informed and better able to see through the hype that's abundant.

I am trying to calculate the numbers but I dont have all the data

Therm cost of 40cents ... how many KW would I need to make one therm?
at $25K system cost after rebates lets say for 20KW system I am making electricity at around 5 cents I believe,,, (did not do an actual calculation) somene might be able to help with that.

I am having a hard time calculating the KW to Therm comparison
google says 1 Therm = 30 KWHour is that what we are working with really? does not seam right...

meaning 1 Therm at 40 cents gives me the same heat as 30 KW of electricity at 22cent *30kw= $6.60 from PSEG or 4cent*30KW= 1.20$ from Solar?

[doctorman]

that is not a heat pump. It is an air conditioner.

thank you for correcting me...

[organic farmer]

Doctorman

I live in Maine. In this region there are more and more people doing net-zero homes [self-heating and self-powered design].

While you are a good deal South of me, your design is also a good deal larger than mine.

Home heating is a huge task for photovoltaic. It takes a lot of wattage to make heat. Solar-thermal is way more efficient for home heating.

At the heart of a heat pump is a freon compressor. Freon compressors suck up a lot of wattage for what they do. If you looked at solar-thermal panels, you can make a lot of heat for very little wattage.

Each state is different. Here in Maine a net-metering system will cost you close to double the price tag of an off-grid system with battery-bank. If there is some other source of benefit for net-metering than great

... my goal is to leave comfortably in the house and not worry about paying for energy needed for the house.

Which is the idea behind net-zero home design

... Geothermal is not an option as the city code prohibits it.

Again that requires freon compressors.

[ButchDeal]

The XP-25 is the heat pump and would provide efficient heating particularly at medium cold weather. It would be a very efficient system bundled with gas furnace for coldest days.

http://www.lennox.com/products/heating-cooling/heat-pumps/xp25

[doctorman]

The XP-25 is the heat pump and would provide efficient heating particularly at medium cold weather. It would be a very efficient system bundled with gas furnace for coldest days.

http://www.lennox.com/products/heati...eat-pumps/xp25

Thank you
honestly not sure I get the difference between the XC25 and XP25
I have to do some reading

can someone tell me how much my electricity costs me from solar if I pay around $25K for a 20KW sytem?
would I get my money back from PSEG at 4 to 5 cents buy back price?

[ButchDeal]

Thank you
honestly not sure I get the difference between the XC25 and XP25
I have to do some reading

can someone tell me how much my electricity costs me from solar if I pay around $25K for a 20KW sytem?
would I get my money back from PSEG at 4 to 5 cents buy back price?

The difference is simple XC25 is an air conditioner. XP25 is a heat pump. A heat pump cools just like an air conditioner but also heats in the winter time.
I heat and cool my house with a heat pump. Heat pumps get less and less efficient as you start getting down in outside temperature as they have a bigger difference to over come. So having a backup source of heat is important. So if you were to have a heat pump and a gas furnace. The heat pump would likely take care of all your heating as long as the outside temperature is above freezing, and it would do a smaller portion of your heating when it is between say 0 and 32 outside, with gas doing the rest.
The more efficient heat pumps are better at lower temperatures than older ones.

[J.P.M.]

Thank you
honestly not sure I get the difference between the XC25 and XP25
I have to do some reading

can someone tell me how much my electricity costs me from solar if I pay around $25K for a 20KW sytem?
would I get my money back from PSEG at 4 to 5 cents buy back price?

You need a bit of education in energy equivalence and conversion efficiency.


1 therm of nat. gas has a commonly accepted upper heating value of 100,000 BTU.
1 therm of nat. gas burned in a furnace or boiler will deliver (100,000 BTU) X ( efficiency of heating device).
The efficiency of most residential heating devices that use nat. gas ranges from ~ 70 % for older/std. units to up to ~ 93-95 % for high efficiency units, less ducting/piping losses, where some of those delivery losses can be treated as uncontrolled gains to the heated space.

1 kWh of electricity has an energy heating value of 3,412 BTU when used as resistance heating. So, 1 therm = 100,000/3,412 = ~ 29.3 kWh of electric resistance heat.
When used to drive a heat pump, 1 kWh of electricity has a heating value of (3,412) X (C.O.P.) when used to drive a heat pump.
Common C.O.P's used to run ~ 3.0 or so and dropped quite a bit as the temp. went down, making them suitably for mild climates, and more marginal the colder the climate became. More recent improvements, including refrigerants, have improved C.O.P.'s to generally somewhere between 4 or 5 when operating in moderate environments, and still only about 20% or so of the max. theoretical value.

The C.O.P. of a heat pump will vary with the outside temp. The colder it gets outside, the lower the C.O.P.

The EER ( Energy Efficiency Ratio) of a heat pump == C.O.P X 3.412
The seer of a heat pump ~~ = EER/.875 to a 1st approx.

Info on C.O.P. and how to calculate a theoretical max. value as f(heat source temp.) can be found in Thermodynamics texts. Until someone figures out how to violate the 2d law of Thermodynamics, practical and achievable C.O.P. values will be lower.

Part of the answer to whether or not you would get your money back on solar depends on how you calculate the cost per delivered kWh of electricity form a PV system. One comprehensive way is to use like cycle costing or process economics. A version of that is to calculate something called the Levelized Cost Of Electricity ( LCOE), taking account of variables as you see fit.

The calcs usually involve making some assumption about the future, such as rates, rates of energy and general inflation, how long the analysis is and lots of other stuff, depending on how involved the person paying the bills wants to get. It's a worthwhile calculation, one reason why being that it points up how/why it ,may not be a good idea to expect most such calcs to be extremely accurate at predicting the future. Still, better than the moron payback that calculates payback = initial net cost/initial savings or some such stuff.

[Sunking]

You need a bit of education in energy equivalence and conversion efficiency.

Ditto.

Doctorman you are about to do something you will regret the hard way, loosing a lot of money.

[DanKegel]

I hope you're ventilating the house properly; sealing up a house really tight without adding proper ventilation can cause problems.

How did you pick 20 KW? What's your electricity use now?

In general, if you're trying to save money, use natural gas everywhere you can (furnace, water heater, stove) instead of solar electric. $0.40/therm is a steal.

That said, if you get heat pumps instead of A/C's, you can use any excess solar to do a little bit of your heating. No idea if that pencils out.

[J.P.M.]

I hope you're ventilating the house properly; sealing up a house really tight without adding proper ventilation can cause problems.

As a practical matter, using current construction techniques, and taking reasonable cautions to ensure all sources of combustion inside a dwelling are properly vented, which includes considerations and measures for air for combustion as well as exhaust, and also moist air removal/exchange, it's pretty difficult to make a house so tight that the indoor air quality will suffer. Possible, but not very likely. Odor control then usually becomes a situation of hygiene and housekeeping.