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A GreenBuildingAdvisor question describes plans to consider a small electric boiler for radiant slab heat in a highly insulated, 600-square-foot Vermont cabin. The owner estimates a 4–6 kW unit may be enough, but the post does not report a final equipment choice, heat-load calculation, or operating-cost comparison.
A 600-square-foot cabin owner in southern Vermont is considering a 4–6 kW electric boiler to keep a radiant-heated slab comfortable, while relying on a mini-split and wood stove for other heat. The question, posted to GreenBuildingAdvisor, describes an early-stage decision rather than a confirmed installation; no heat-load calculation, boiler selection, or measured cost comparison is provided.
The owner says the cabin is well insulated, with a slab insulated by 3 inches of XPS foam, 4 inches of continuous exterior wall insulation, and 6 inches of continuous roof insulation. The home also has a 12,000-BTU hyper-heat mini-split in the main living area and a small soapstone wood stove. The proposed boiler would serve the hydronic tubing in the slab, not necessarily act as the home’s sole heat source.
The owner’s stated goal is to run the radiant system at a relatively low level, making the floor comfortable underfoot during winter. They estimate that a 4–6 kW unit might fit the home’s needs, but present that as their own estimate, not as a result verified by an installer or heating-load analysis. The post says space is limited and cites lower initial cost and smaller equipment size as reasons to explore electric resistance heat.
The owner acknowledges that other options, including a heat-pump water heater, may be preferable in some respects. They also say Vermont electricity rates are “pretty comparable to propane.” The source does not provide rate figures, tariffs, equipment quotes, or an operating-cost calculation to establish how the options compare for this particular cabin.
Sizing a Small Cabin’s Backup Heat
The question highlights a practical decision for a small, highly insulated home: whether to add a compact heat source for floor comfort when other equipment already provides space heating. A boiler that is inexpensive and physically small could appeal to an owner with limited mechanical-room space, but its suitability depends on the building’s actual heat demand and how the systems will operate together.
Electric resistance boilers turn electricity into heat at the point of use, while a heat pump moves heat and may deliver more heat per unit of electricity under suitable conditions. That distinction can affect running costs, but the source gives no local rate data or system performance figures for this home. Without those inputs, the owner’s reported comparison with propane cannot settle which option would cost less over time.
The case also shows why a small floor area alone does not establish the required boiler size. Insulation, air leakage, design temperatures, slab response, and the extent to which the mini-split or stove supplies heat all affect the demand. A professional heat-loss calculation would be needed to test the proposed capacity rather than treating the owner’s estimate as a confirmed specification.
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The Cabin’s Existing Heating Setup
The post is a request for advice, not a report of a completed project or a general finding about electric boilers. The owner describes a single cabin in southern Vermont and asks people with experience of small electric boilers to comment on the approach. The home’s insulation details and existing heat sources are relevant because the radiant slab is intended to provide gentle warmth, while the mini-split and wood stove may contribute to heating the living space.
The owner frames the decision around initial cost, equipment size, and electricity prices, and says they have already read discussions of electric boilers. They recognize heat-pump-based alternatives but want to explore electric resistance equipment for this particular, space-constrained project. The source contains no follow-up confirming which system was ultimately chosen or installed.
“My intention with the radiant is to keep it relatively low, but just warm enough to have comfortable toes on the floor in the winter.”
— The cabin owner, in the GreenBuildingAdvisor question
small electric hydronic boiler 4kW
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Boiler Capacity and Running Costs
The source does not establish whether 4–6 kW is enough for the cabin, whether the boiler would supplement or replace any other heating during cold weather, or how often the slab would run. No design heat-loss figures, floor-loop layout, water-temperature requirements, electrical-service capacity, or installer assessment are reported.
It is also unclear what the owner means by electricity and propane rates being comparable: the post gives no units, billing period, delivery charges, appliance efficiencies, or projected annual consumption. There is no quote for the electric boiler or alternative equipment, and no confirmed installation or later performance report. The proposed system and expected savings or costs therefore remain unverified.
electric boiler for small home slab heat
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Load Calculation Before Equipment Choice
The next useful step would be to calculate the cabin’s design heat loss and assess how the slab, mini-split, and wood stove are expected to share heating duties. An HVAC professional familiar with hydronic radiant systems can use those details to evaluate boiler capacity and system controls. The owner would also need to check the home’s electrical service and compare equipment and operating costs using current local energy prices.
No decision or follow-up is included in the source material. Until the owner reports a selected system, installed capacity, or actual winter energy use, the question remains an evaluation of a possible heating approach—not evidence that a 4–6 kW electric boiler will meet the cabin’s needs or cost less than the alternatives.
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Key Questions
Has the cabin owner installed an electric boiler?
The source is a request for advice and does not report a final equipment choice or installation.
Is a 4–6 kW boiler confirmed as sufficient?
No. The figure is the owner’s preliminary estimate. The post provides no heat-loss calculation or professional sizing assessment.
What heating equipment is already in the cabin?
The owner reports a 12,000-BTU hyper-heat mini-split in the main living area and a small soapstone wood stove, in addition to the proposed radiant slab system.
Does the source show that electric heat costs about the same as propane?
No. The owner says Vermont electricity rates are comparable to propane, but gives no rate figures or operating-cost comparison for the cabin.
Source: rss
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