Electric or Propane Boiler Recommendations for Radiant?
Hi All,
I searched but didn’t find any clear winners in the option of an electric boiler.
With technology evolving I thought I’d ask to see if anyone has actual positive experience with an electric boiler?
Ideally I’d like to stay away from propane if possible, but I’m also a pragmatist so can adjust if needed. I asked my local architect about heat pump boiled I’d read about but he felt in our winter climate it’s not recommended.
Background:
– Western Montana new construction (Bitterroot Valley)
– Frost walls with slab
– Ground floor floorplan attached est 1200sf (not all windows in yet but you’ll get the gist)
– 2nd floor will be above the bedroom/garage that includes: office, bedroom and 1br guest suite for long term guests/family. Plan to block off and have separate heating zone for all but the office in normal use to minimize heating required.
– HVAC plan – hydronic radiant with a mini split in great room building for better temp control flexibility and AC on handful of hot summer days.
– Backup heat of mini split and zc wood burning fireplace
– Electricity rates = .068 – .076 per kwh (mostly hydro powered)
– Propane rates = $2.3-$2.8/g when filling large tanks
– Propane tank is already planned for: stove and as fuel for backup generator since it stores so much better than gas/diesel.
– Will focus on insulation and building envelope but…Mountain Views (video attached) are stunning from SW to NW so I’ll be sucking it up and sacrificing some of the thermal envelope to enjoy them.
Thank you,
Steve
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Replies
Quick opinion (assuming well insulated/air sealed envelope).
Cheap way: Electric resistance radiant floor heating. Simple no moving parts.
Deluxe way: Ground source heat pump water-to-water hydronic radiant heat.
Note that with those cheap electric rates the deluxe way would likely have a payback of 50 years or more (just guessing).
Maybe best bang for buck: Triple pane windows and curtains for night time.
Resistance electric is significantly (33%) cheaper at the lower rate scenario, even more at the higher rate scenario, so ditching propane for central heat is an easy decision. Now: are radiant floors required in a new house with higher levels of insulation? That's less economic and more personal and many GBA articles have been written about it, usually opposed to in-floor hydronic systems (especially in slabs). If radiant floors are a must, then electric boiler vs. electric mats are the next decision: electric tubing allows you to switch to an air-to-water heat pump down the road, but will be more expensive upfront for the same initial efficiency. They also provide zero cooling, so you'd be doubling up on those costs. Hydronics is generally more expensive to begin with than using ductwork and scales very poorly for houses your size.
The cheapest option to operate and install would be air-source heat pumps, ducted or ductless or a mix. That would be about 66% cheaper to operate compared to the electric boiler/mats, ~80% cheaper than propane. Your architect is misinformed, they will have zero problem in your climate and easily pair with electric/propane backup systems.
Thanks for the input guys.
So IF electric boiler, do you know any brands more highly recommended from long term experience users?
Radiant or not?
Yes, I've definitely read the studies and opinions about it and am leaning towards it because I'm a little tired of the noise and breeze of the ducted central hvac. I had an air source heat pump previously in NorCal. Also, from a purely feedback perspective, anyone I've spoken with who has or has had radiant heated floors LOVE them. Beyond the numerical calculations I figure there's something to overwhelming opinion in favor of them for quality of life.
Not dead set on radiant, but certainly heavily leaning towards it.
Local architect is totally good with air source heat pump for hvac (with propane backup I believe) just didn't recommend for the hyrdronic radiant boiler.
From what you're both saying and another online propane v electric calculator I did, it seems I can at least rule out propane as long I can find a well sized, reliable electric boiler for my application.
Does anyone have good experience with a heat pump water heater or hydronic heater in cold climates?
The fact your electricity is so cheap, anything propane is a non starter unless you regularly need a backup generator.
If you must have floor heat, your best option is what Denis recommends. Standard resistance mat.
The ROI for anything hydronic with the heat coming from a ASHP or GSHP is measured in centuries.
If you want slightly lower operating cost is combine the resistance floor heat with ducted heat pump. The idea is to provide heated areas where there is high foot traffic but not the full slab, this way the heated areas can run warmer. The floor heat would also only provide part of the heat and only during daylight hours whereas the heat pump would provide supplement heat during the day and all the heat during the night.
Add in a fancy ERV, you are still well under $10k in materials and a much simpler install and lower operating cost.
Cold climate heat pumps have come a long way, no need for backup heat even if your temperatures dip well bellow 0F.