How much supplemental heat would I need trying to heat a home with PV in Iowa?

[spazatak]

I keep reading for people trying to heat their home in cold climates with PV, that the coldest months are the most challenging which is understandable.
So does this lead them to oversize the PV system to meet load during these coldest months?

And when my utility company tells me I can only size my PV system to 80% of my load when grid tied, how much of that will I actually get during these coldest months?

And could I power resistance heaters with PV without a grid tied charge controller or batteries?

Thanks

 

[RV10flyer]

I keep reading for people trying to heat their home in cold climates with PV, that the coldest months are the most challenging which is understandable.
So does this lead them to oversize the PV system to meet load during these coldest months?

And when my utility company tells me I can only size my PV system to 80% of my load when grid tied, how much of that will I actually get during these coldest months?

And could I power resistance heaters with PV without a grid tied charge controller or batteries?

Thanks

I heat my home with 20-33 SEER inverter heat pumps, down to around 30F. Below that, you’ll need wood or gas heat to supplement. Don’t even think about running resistance heaters. Start with a small, well insulated home with a heat pump water heater. In Dec-Feb, you’ll get about 5% of the power that you’ll get in May-July. Oversize your pv. Sure you could power resistance heaters during the day with 10-20kWp and heat a well insulated 1800 sq ft home. The problem is at night when it’s the coldest outside.

 

[Shimmy]

This is one of the reasons over-sizing your PV with an off-grid system for supplemental works.

The tighter (well insulated, no air leaks, energy recovery unit, etc) your home the easier it is to make it possible. In a climate like Iowa I would also think ground source heat pumps are going to be better than air-source; I think you get pretty high winter humidity.

Then there are things like how well the house is designed for passive solar. For an existing house though a wood burning stove is likely the minimum required for winter supplemental heat.

 

[HarryN]

Iowa is a good example where wind might make more sense than solar for winter energy production.

In the late 1970s I lived in Muscatine and what i remember is that the sky was pretty over cast during the day and more clear at night in the winter (releasing the heat to the sky ).

Generating 1 - 4 kW of power, 24 hrs / day in the winter in IA might be fairly easy using wind compared to doing that with solar.

In the midwest, you can't really rely on just one thing - especially in the winter.

This simplistic looking outfit is actually quite a strong resource and supplier of wind supplies.

KANSAS WIND POWER since 1975

Kansas Wind Power since 1975. A good source for solar, wind & hydro electric independent power systems, energy saving products, water pumping, solar cookers, DC lights, gas refrigerators, composting toilets, shortwave radios and telescopes for homes, cabins, farms, boats, RV's.

kansaswindpower.net

 

[Zwy]

I keep reading for people trying to heat their home in cold climates with PV, that the coldest months are the most challenging which is understandable.
So does this lead them to oversize the PV system to meet load during these coldest months?

You can try however you know in an Iowa winter there are many days that are overcast. Air source heat pumps can work on the warmer days, but you will need some type of heat that is not from PV, especially when it is below 20F for days on end. You will be better served to use the electricity for running a gas or wood furnace/boiler.

If you want to go with a ground source heat pump as an example, you can purchase from utility at a winter rate in most of Iowa and the cost is not much more than the cost of production but will require a second meter. For example, Alliant Energy runs in steps for winter rates, as more Kwh is used, the rate goes down. First step is $0.099, second step is $0.077, third step is $0.039. If you enroll in nights and weekends off peak, those rates are halved. https://www.alliantenergy.com/waystosave/savingsprograms/timeofdaypricingiowares

Pretty hard to compete with $0.019 per Kwh. The generator has to have a minimum of capacity online and as a result, they will sell it cheap in order to recoup some of that cost. You can't build PV that cheap.

And when my utility company tells me I can only size my PV system to 80% of my load when grid tied, how much of that will I actually get during these coldest months?

The rules are changing in Iowa quickly because there were many large PV systems installed by farmers and homeowners. The grid tie systems are getting capped. For example, a farmer installed grid tie PV to build a bank for grain drying in the fall. His rural coop has now sent him a letter stating he can only bank 2,000Kwh and the coop gets the excess for free. 2,000Kwh doesn't last long running 15 hp motors 24/7.

The biggest thing I see with grid tie in Iowa is the PV array is usually covered with snow for weeks on end. If the sun does come out, it takes several days for the snow to clear off. You will see the snow slide down until it hits the aluminum frame, then freeze there during cold spells (high pressure, sunny days, no cloud cover). So there never is a yield for most of the winter. These systems were built cheap and as a result, the PV is not seasonally adjustable.

I purposely went with an off grid system due to the rules change quickly in Iowa as the Utilities Board seems to let the utilities do what they want. The daily rate (meter charge) has seen 50 to 60% increases while the rate per Kwh has remained the same. Take for instance an elderly household of one person that uses 10Kwh per day. If the daily rate goes from $1.20 to $1.80, that makes a huge difference in the cost per Kwh. Instead of $0.18/Kwh, it becomes $0.24/Kwh.

The second reason is I can produce all the electricity I want and use it in an off grid system. I'm not limited to 80% of normal grid usage.

And could I power resistance heaters with PV without a grid tied charge controller or batteries?

Thanks

Resistance heater is fine for a dump load when you have excess. I would only use it for excess dump load. You actually might be better served using a air source heat pump down to about 10F as a dump load.

I would not rely on electric (resistive or air source heat pump) as major heat source for Iowa in winter.

 

[spazatak]

You can try however you know in an Iowa winter there are many days that are overcast. Air source heat pumps can work on the warmer days, but you will need some type of heat that is not from PV, especially when it is below 20F for days on end. You will be better served to use the electricity for running a gas or wood furnace/boiler.

If you want to go with a ground source heat pump as an example, you can purchase from utility at a winter rate in most of Iowa and the cost is not much more than the cost of production but will require a second meter. For example, Alliant Energy runs in steps for winter rates, as more Kwh is used, the rate goes down. First step is $0.099, second step is $0.077, third step is $0.039. If you enroll in nights and weekends off peak, those rates are halved. https://www.alliantenergy.com/waystosave/savingsprograms/timeofdaypricingiowares

Pretty hard to compete with $0.019 per Kwh. The generator has to have a minimum of capacity online and as a result, they will sell it cheap in order to recoup some of that cost. You can't build PV that cheap.



The rules are changing in Iowa quickly because there were many large PV systems installed by farmers and homeowners. The grid tie systems are getting capped. For example, a farmer installed grid tie PV to build a bank for grain drying in the fall. His rural coop has now sent him a letter stating he can only bank 2,000Kwh and the coop gets the excess for free. 2,000Kwh doesn't last long running 15 hp motors 24/7.

The biggest thing I see with grid tie in Iowa is the PV array is usually covered with snow for weeks on end. If the sun does come out, it takes several days for the snow to clear off. You will see the snow slide down until it hits the aluminum frame, then freeze there during cold spells (high pressure, sunny days, no cloud cover). So there never is a yield for most of the winter. These systems were built cheap and as a result, the PV is not seasonally adjustable.

I purposely went with an off grid system due to the rules change quickly in Iowa as the Utilities Board seems to let the utilities do what they want. The daily rate (meter charge) has seen 50 to 60% increases while the rate per Kwh has remained the same. Take for instance an elderly household of one person that uses 10Kwh per day. If the daily rate goes from $1.20 to $1.80, that makes a huge difference in the cost per Kwh. Instead of $0.18/Kwh, it becomes $0.24/Kwh.

The second reason is I can produce all the electricity I want and use it in an off grid system. I'm not limited to 80% of normal grid usage.


Resistance heater is fine for a dump load when you have excess. I would only use it for excess dump load. You actually might be better served using a air source heat pump down to about 10F as a dump load.

I would not rely on electric (resistive or air source heat pump) as major heat source for Iowa in winter.

Hi neighbor, and thanks for all this great information I'm still digesting. I did get information from TIP rural electric cooperative. Currently I'm paying $0.13 a kWh for the first 250 then it drops to $0.09. If I install a air source heat pump I get a $400 rebate and the price goes down to $0.077 per kWh with a dedicated meter. If I buy a PV grid tie system I don't qualify for the winter rate and they buy back my excess production at 2.7 cents per kWh.

I'm curious what you think, and would/are doing considering you're in Iowa.

Thanks

 

[Zwy]

Hi neighbor, and thanks for all this great information I'm still digesting. I did get information from TIP rural electric cooperative. Currently I'm paying $0.13 a kWh for the first 250 then it drops to $0.09. If I install a air source heat pump I get a $400 rebate and the price goes down to $0.077 per kWh with a dedicated meter. If I buy a PV grid tie system I don't qualify for the winter rate and they buy back my excess production at 2.7 cents per kWh.

I'm curious what you think, and would/are doing considering you're in Iowa.

Thanks

I went off grid with my house basically. I have an acreage and there still is utility power for the shop and other out buildings but the house runs off grid with batteries. Your rate is cheaper than Alliant I have here. I see you are from mid central Iowa area. I'm up in NE IA. One would not thin there would be that much difference in weather but I have to take the trip to Des Moines or Iowa City and just those 130 miles makes a difference.

With the heat pump dedicated meter, do you have another daily charge for that meter? That raises the cost per kwh if it does.

I installed an air source heat pump ($1500 cost) for air conditioning in summer and heating fall/spring. I'll collect the $450 tax credit, Alliant would maybe rebate $50 so not worth the trouble. Federal tax credit on qualified equipment is 30% from Inflation Reduction Act. Next year I'm considering adding another air source heat pump and take the credit again. I highly recommend installing heat pumps and taking the tax credit. This reduces the gas usage during at least spring and fall and the bonus is the air conditioning takes very little power with the inverter heat pumps.

I plan on using the heat pump for heating when outdoor temps give a return on COP and for a dump load for excess PV. My main heat source will remain LP gas, although I have a large amount of ash to cut down due to emerald ash borer. So I may add an outside wood boiler for main heat. I have access to timber on the farm, I grew up in a house heated entirely with wood.

If your utility is paying for rebates like that, I'd install all the heat pumps you will need, collect the rebates and tax credits. Then start the move to an off grid system. You can do it in stages, such as a system to run just the heat pumps, then expand later.

My opinion is grid tie in Iowa is dead. The rules are changing. Contracts get thrown out, my brother put up a 17.5Kwh wind generator and sold excess for $0.10/Kwh but the REC merged with another and threw the contracts out. Now he is net meter with a limit on his bank. They thought they would get the excess for free but he now builds the bank, then locks down the generator to keep from wearing it out. When he needs to build the bank up again, he lets it run.

I looked at TIP site but can't find rate schedule/meter/energy charges. Those add up and affect the total cost per Kwh. Your rates are cheap but what about other fees and your total usage per month.

 

[spazatak]

I went off grid with my house basically. I have an acreage and there still is utility power for the shop and other out buildings but the house runs off grid with batteries. Your rate is cheaper than Alliant I have here. I see you are from mid central Iowa area. I'm up in NE IA. One would not thin there would be that much difference in weather but I have to take the trip to Des Moines or Iowa City and just those 130 miles makes a difference.

With the heat pump dedicated meter, do you have another daily charge for that meter? That raises the cost per kwh if it does.

I'm not certain. Ive read the website but cant find the info..

I plan on using the heat pump for heating when outdoor temps give a return on COP and for a dump load for excess PV. My main heat source will remain LP gas, although I have a large amount of ash to cut down due to emerald ash borer. So I may add an outside wood boiler for main heat. I have access to timber on the farm, I grew up in a house heated entirely with wood.

If your utility is paying for rebates like that, I'd install all the heat pumps you will need, collect the rebates and tax credits. Then start the move to an off grid system. You can do it in stages, such as a system to run just the heat pumps, then expand later.

My opinion is grid tie in Iowa is dead. The rules are changing. Contracts get thrown out, my brother put up a 17.5Kwh wind generator and sold excess for $0.10/Kwh but the REC merged with another and threw the contracts out. Now he is net meter with a limit on his bank. They thought they would get the excess for free but he now builds the bank, then locks down the generator to keep from wearing it out. When he needs to build the bank up again, he lets it run.

I got that feeling grid tie in Iowa is dead too. T.I.P. pays 2.7 cents per kWh backfeed. I'll assume most people feel that's not enough to justify a GT system?

If you're suggesting air cooled heat pumps because of the winter rate, why would I need a off grid PV system? What would I use it for?

I looked at TIP site but can't find rate schedule/meter/energy charges. Those add up and affect the total cost per Kwh. Your rates are cheap but what about other fees and your total usage per month.

Yeah I'm not sure. I've already called them once so I don't want to bother them so soon. But I'll find out

 

[Zwy]

I'm not certain. Ive read the website but cant find the info..

It should be on your bill.

I got that feeling grid tie in Iowa is dead too. T.I.P. pays 2.7 cents per kWh backfeed. I'll assume most people feel that's not enough to justify a GT system?

It appears to be wholesale price. MI Energy won't even pay the 2.7 cents for excess once the bank is full, they get it for free.

If you're suggesting air cooled heat pumps because of the winter rate, why would I need a off grid PV system? What would I use it for?

I would install the heat pumps and collect the rebate. Lowers your cost. Then begin to adopt an off grid PV system to run the units. But you need to keep your long term cost below the long term winter rate to make it pay. Unless you want/need backup power. If the utility charges another daily fee for the meter, this needs to be factored in. That is why I asked about 2 meter charges or just one.

Yeah I'm not sure. I've already called them once so I don't want to bother them so soon. But I'll find out

If they don't give an answer, contact the Iowa Utilities Board and tell them you can't seem to find information on the basic charges. I guarantee you will get an answer pretty quick.