What Are the Disadvantages of a Heat Pump?

Higher upfront cost than a basic furnace or boiler

An air-to-water heat pump system usually costs more upfront than a standard gas furnace or an entry-level boiler. The heat pump itself, the hydro station, tanks, and installation all add cost that a simpler combustion system does not carry in the same way.

This is a real tradeoff, not a myth. What often changes the math is operating cost: a heat pump moves heat instead of creating it from fuel, so it can produce several units of heat for every unit of electricity it uses. At a moderate 41°F outdoor temperature, an APOLLO air-to-water heat pump delivers a COP (coefficient of performance) up to 4.6 — about 4.6 times more heat energy out than electrical energy in.

MBTEK does not publish fixed system pricing here because it depends on heat pump size, hydro station, tanks, distribution, and installation. A specialist can walk through the real numbers for your specific project, including any rebates or incentives available in your area, before you commit.

Heating output and efficiency drop as it gets colder

This is true of every air-source heat pump, including MBTEK's APOLLO line. As outdoor temperature falls, there is less heat energy available in the outdoor air to move indoors, so both heating capacity and efficiency decrease.

The APOLLO 3.5 Ton is a useful example: at 41°F outdoor, it delivers 42 KBTU of heating with a COP of 4.6. At 10°F outdoor, output drops to 22.2 KBTU with a COP of 2.11 — still producing more heat than the electricity it consumes, just less efficiently than on a mild day.

Two things limit how much this matters in practice. Every APOLLO and APOLLO MAX model is rated to heat reliably down to -31°F outdoor — it does not simply stop working in the cold. And the Hydro Smart Station adds a 15 kW, 2-stage electric backup heater (5 kW / 10 kW / 15 kW) that automatically covers the coldest days, so the building is never left short on heat while the outdoor unit is working harder than usual.

Standard models can't reach the water temperatures baseboards or radiators need

Baseboards and radiators are designed around hot water — often 160°F or higher — the way a boiler supplies it. The standard APOLLO air-to-water heat pump line tops out at 131°F, which is enough for radiant floors and fan coils but not enough for most baseboard or radiator systems.

APOLLO MAX solves this specific limit: it reaches up to 170°F, hot enough to run baseboards and radiators directly. It also happens to be quieter and more efficient in cold weather than the standard line, at a higher price point.

If your distribution is radiant floor or fan coils, standard APOLLO is usually the better value. If you have baseboards or radiators — or you specifically want the quietest, most efficient cold-climate performance — APOLLO MAX is the model that actually solves it.

It runs on electricity only — there is no off-grid backup

An air-to-water heat pump needs electrical power to run, full stop. Unlike a wood boiler, it cannot burn fuel to keep a building warm during an extended power outage or on a site without reliable grid power.

This is a genuine limit, and there is no MBTEK product that removes it — a heat pump is an electric appliance. If off-grid or no-electricity operation is a real requirement for your project, MBTEK's PRO wood boiler line is built specifically for that case; a heat pump system is not the right fit here.

For most homes with normal grid service, this is a non-issue. It only matters for remote sites, frequent extended outages, or a deliberate off-grid design.

More mechanical-room components to plan than "just a boiler"

A basic boiler can be close to a single appliance. A complete air-to-water heat pump system typically includes the outdoor heat pump, an indoor hydro station, pumps, glycol pressurization equipment, backup heat, a DHW heat exchanger or tank, and controls. That is more to plan, source, and install than a single boiler.

This is exactly the problem the APOLLO Hydro Smart Station is designed to solve. Instead of sourcing and piping together separate pumps, a backup heater, a DHW heat exchanger, an expansion tank, and controls as loose field components, the Hydro Smart Station combines them into one pre-assembled indoor unit: dual circulator pumps, a 15 kW 2-stage backup heater, a stainless DHW heat exchanger with its own pump, push-button glycol pressurization, and Wi-Fi touchscreen control, all in one station with isolation valves and quick-connect wiring for service access.

Fewer loose components means less time piping the mechanical room together, fewer connection points that can leak or fail, and one station to service instead of five separate parts — which is a real, direct answer to both installation complexity and installation cost.

Performance depends entirely on correct sizing and design

A heat pump that is undersized, oversized, or paired with the wrong distribution method will disappoint, even though the equipment itself is not at fault. Getting sizing right depends on square footage, insulation, heat loss, climate, and how the water will be distributed: radiant floor, fan coil, or baseboard/radiator.

MBTEK sizes air-to-water heat pumps by matching square footage and distribution type to one specific model, never guessing at the largest unit "to be safe" or leaving a customer to pick from a list alone. For any property over 6,000 ft², or over 4,000 ft² needing MAX-tier hot water, MBTEK will say so directly and bring in a specialist for a multi-unit design rather than force-fitting a single model.

These sizing ranges are always approximate starting points. Final sizing depends on heat loss, insulation, climate, and distribution design — confirm with an MBTEK specialist before ordering. See the heat pump sizing guide for the full model-by-model breakdown.

The disadvantages are real — most are solvable

A heat pump costs more upfront, loses some output in extreme cold, and needs more mechanical-room planning than a single boiler. Standard models cannot run baseboards or radiators, and none of them work without electricity.

For homes with reliable grid power and the right distribution method, every one of these limits except off-grid operation has a practical design answer, starting with matching the right APOLLO series to your project and simplifying the mechanical room with the right hydro station. See what a heat pump is, how it compares to a mini-split, or the APOLLO installation planning guide for more detail.