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A GreenBuildingAdvisor question describes a homeowner considering a small electric boiler for radiant slab heat in a well-insulated 600-square-foot Vermont cabin. The owner estimates a 4–6 kW unit may suit the goal of mildly warm floors, but no heat-loss calculation, operating-cost comparison or final equipment choice is reported.
A Vermont homeowner is considering a 4–6 kW electric boiler to warm the insulated concrete slab in a 600-square-foot cabin, while relying on a mini-split and wood stove for other heating. The GreenBuildingAdvisor discussion presents the system as an option under consideration, not a confirmed installation, and does not establish whether the proposed boiler size or expected costs are suitable.
The cabin owner says the slab has 3 inches of XPS insulation, with 4 inches of continuous exterior insulation on the walls and 6 inches on the roof. The owner describes the building as very well insulated and says limited space is one reason for considering a compact electric boiler rather than a larger heating setup.
The existing heat sources are a 12,000 Btu/h Hyper-Heat mini-split in the main living area and a small soapstone wood stove. The owner says the planned radiant system would run at a relatively low level, mainly to keep the floor comfortable underfoot in winter—not necessarily to carry the cabin’s full heating load.
The homeowner estimates a 4–6 kW boiler might be enough and says electricity rates in Vermont are comparable to propane rates. Those are the homeowner’s estimates and assessment; the source provides no utility bill, rate figures, heat-loss calculation, equipment quote or operating data to verify them.
Sizing a Small Cabin’s Floor Heat
The question matters to homeowners weighing lower upfront equipment cost and limited mechanical-room space against energy use over time. An electric resistance boiler can provide hydronic heat without combustion equipment, but the source does not quantify installation costs or compare seasonal bills with propane, a heat pump or the cabin’s existing mini-split.
The distinction between comfort heating and whole-home heating is central. A system intended to keep a floor mildly warm may have a different capacity requirement from one expected to maintain indoor temperatures during Vermont cold spells. The reported insulation details help describe the building, but they do not replace a design heat-loss estimate or establish the boiler’s appropriate size.
Because the cabin already has two other heat sources, any decision also depends on how the systems would be operated together, the desired floor temperature, and the hydronic system’s controls. The discussion raises those practical questions but does not report answers or a completed design.
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Existing Heat and Insulation
The source is a homeowner’s request for personalized advice in a GreenBuildingAdvisor question, rather than a project announcement, product test or documented installation. The owner acknowledges having read earlier discussions about electric boilers and says heat-pump water-heating options may offer advantages, while asking specifically about electric equipment’s initial cost and compact size.
The reported setup combines a slab with insulation beneath it, continuous insulation on the cabin’s walls and roof, a mini-split and a wood stove. That combination provides relevant context, but the source does not give the cabin’s air-leakage rate, window specifications, design indoor temperature, local design outdoor temperature, floor tubing layout or measured heating demand. Without those details, readers cannot treat the proposed capacity as a verified recommendation.
“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 hydronic electric boiler 4-6 kW
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Capacity, Bills and Installation Details
The source does not state whether the owner ultimately installed an electric boiler or received a definitive sizing recommendation. It also does not establish whether a 4–6 kW unit can meet the intended floor-comfort goal under local winter conditions, or how much electricity the system would use.
Important variables remain unreported, including the cabin’s calculated heat loss, the radiant slab’s design and controls, electricity and propane prices for the relevant billing periods, and equipment and installation costs. The owner’s claim that rates are comparable is not supported by a dated tariff comparison. No independent cost analysis or measured performance is included.
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Heat-Loss Review Before Choosing
The next useful step would be a room-by-room heat-loss calculation and a design review of the slab and hydronic controls by a qualified heating professional. Those checks could clarify whether the proposed capacity is intended only for floor comfort or must also cover a defined share of the home’s heating load.
A homeowner comparing options would also need current local electricity and propane rates, equipment and installation quotes, and an estimate of seasonal use. The source reports no scheduled decision, installation or follow-up, so the eventual system choice and its performance remain unknown.
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Key Questions
Has the homeowner installed an electric boiler?
The source only describes a system under consideration. It does not report an installation or a final decision.
Is a 4–6 kW boiler confirmed as the right size?
No. That is the homeowner’s estimate. The source includes no heat-loss calculation or design recommendation verifying the capacity.
Would the boiler heat the entire cabin?
The stated goal is to keep the floor comfortable, while a mini-split and wood stove are also present. The source does not say the boiler is designed to meet the cabin’s full heating load.
Are electric and propane costs confirmed to be comparable?
No figures or billing-period comparison are provided. The claim that rates are comparable is the homeowner’s assessment, not a documented cost analysis.
What information would help determine whether the system is suitable?
A heat-loss calculation, the intended indoor and floor temperatures, hydronic design details, local energy rates, and equipment and installation quotes would help inform a comparison. None is included in the source.
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