More efficient options vs heating home with propane boiler
I just bought a home about 6 months ago that is 27 years old in Colorado. It has about 4,000 sqft of heated area through a hydronic system on a propane boiler. There is about a 1,000sqft garage with propane ceiling unit. I work from home and need to keep that warm in the winter. I was surprised to see my propane bill was averaging about $700 per month during the winter and wanted to start looking at ways to improve efficiency this summer.
The insulation looks very good throughout the house. I did notice the crawl space is vented to the exterior and there is thick foam insulation around the foundation but no insulation in the flooring. I would assume with a vented crawl space you would want to have the flooring insulated.
Some things I was looking into:
-Solar panels w/electric boiler or heat pump
-Outdoor wood boiler
-Solar panels w/electric boiler/heat pump and electric heaters or wood stove for garage
If I go solar I don’t want to spend the $$ on battery backup so it would be a grid tied system but it seems like it could be a good option given CO has so many days of sun but it could potentially take a very large grid.
I am just starting to look into this more seriously to take care of it before next winter so any advice would be appreciated!
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Replies
At $700 a month sounds crazy boarding on impossible but maybe getting propane delivered to a remote mountain top is crazy expensive.
In my opinion Hydronic heating is all about comfort with cost be damned.
The first thing to look at a good energy audit, This will include a blower door test to find where the heated air is blowing out of your house and thermal imaging when it is cold outside this will show where you are losing your heat.
Consider adding hiper heat mini splits sized to heat the house down to -10F and run the propane when colder.
Walta
A gallon of propane when burned produces about 93,000 btus. A kilowatt hour is 3412 btus.
A cold climate minisplit heat pump in CO probably has a coefficient of performance (COP) of around 3, meaning that on average you'll get about 10,000 btus from 1 kwh. So 9.3 kwh produces the same heat as a gallon of propane from 100 % efficient boiler.
Your propane boiler has an efficiency rating between 75% and 98%, depending on age and type.
Using the above information, plus your cost per gallon of propane and per kwh, you can calculate the relative cost of heating with propane or a heat pump. For example, if you pay 10¢ per kwh, you'd need to pay no more than 93¢ per gallon for propane to be as cheap as electricity, again keeping in mind your boiler efficiency.
Since CO is so sunny, I'd think solar would be a great investment, along with a minisplit or two. Solar has a 26% federal tax credit this year, going to 22% next year.
Minisplits keep me warm in Maine, zone 6.
Appreciate the info! It sounds like solar is the way to go with minisplits where needed then keep the propane boiler system as is for now.
Based on your calcs Stephen if I am going through an average of 300gal of propane (sometimes more) in the winter that would be equal to a 3.8kWh solar system based on btus using the minisplits. I assume it would need to be significantly larger since that calculation assumes you are getting peak output 24 hours a day.
In terms of getting an energy audit is that usually through a HVAC company?
Walter is correct; we have an oil-fired hydronic heating system and its comfort can't be beat, especially when temperatures dip well below freezing. That said, the bulk of our home's space heating requirements are met by two ductless mini-splits that can provide an equivalent amount of heat at roughly one-half the cost.
In your case, I would look to offset as much of your needs as would be economically feasible, bearing in mind any physical barriers to their placement, either in terms of the indoor air handling unit or outdoor compressor, or restrictions with respect to their airflow/coverage.
I would also look at the possibility of installing a Tekmar Control system or similar fuel management device to allow your boiler to operate more efficiently in response to changes in outdoor temperature.
You should not have to guess at your fuel usage. Every bill should list how many gallons you purchased at what price and list any delivery charges and taxes. If you do not have the old bills most suppliers are happy provide a copy and often the ones from before you bought the home.
You may not be aware not all propane dealers treat their customer ethically, price gouging is a chronic complaint.
You may not own the propane tank. Tank rent is often hidden in a higher price per gallon and no other company will fill a rented tank.
Before you get your tank filled try to shop the price with 3 suppliers.
Walta
Appreciate all the info! Unfortunately I am pretty limited on propane suppliers here. There is one other supplier I will check with in the next month when prices increase.
I have had more time to analyze my average energy usage living in the house longer.
Propane~200 gal/month average (300-350 in winter)
Electric~630 kWh avg/month
I have decided to add a 7.5kW roof solar system and offset heating with electric.
I was looking at a multi zone mini split unit due to their efficiency and recommendations. Due to the size of the house I would likely need to get two units and first was looking at a 42k system to heat my oversized garage (this is where my office is), two bedrooms, and a living area. At some point I will add one to the other side of the house. The cost here is huge though at over 5,500 for just for the one system (not including install, refrigerant, lines, electric hookup, etc).
Another option I was considering would be to replace my propane boiler (145kBtu/hr) with an electric boiler such as Electro Industries EB-CX-36 - 36 kW - 123K BTU. This would allow me to heat the entire house if needed, except the shop where I could add radiant electric heaters. With this though it shows max current draw of 150A and my main panel is only 200A. I assume these might just be for industrial applications rather than home heating. Also at 36kW this could easily use way more power than the solar system although I don't have a good understanding of the kWh that would be used here. If I assume 1 gal of propane is 27kWh of electricity then 200gal/month is 5,400kW. Divide that by 7.5kW system would show that you need 720 hours of sunlight/month. That would be over 3x the amount of electricity produced by my solar system so it does not seem like a good solution.
Overall I am leaning towards the mini split systems due to efficiency but the cost is going to be extremely high. Any other recommendations?