Heaters, Fans, and Air Conditioners

The single biggest mistake buyers make with heating and cooling equipment is picking by category instead of by space. A box fan, a ceramic desk heater, a ductless mini-split, and a whole-home heat pump all “move air” — but they solve completely different problems. Get the match right and the equipment lasts. Get it wrong, especially the sizing, and you’ll pay for it in short equipment life and lousy comfort.

For broader project planning, explore WBC’s building materials resources.

Here’s the plain-language map. Central air or heat pumps are the right call for whole-home cooling if there are existing ducts. Mini-splits, which are ductless, fit spaces without ducts, additions, or zone-specific control. For single rooms or renters, window units offer better efficiency and lower cost, while portable units are a last resort because of lower efficiency, more noise, and a larger footprint.

For supplemental heat, the choices split into two camps. Electric resistance heat comes from centralized forced-air electric furnaces or from heaters in each room — electric baseboard heaters, electric wall heaters, electric radiant heat, or electric space heaters. The portable ceramic and fan-driven units fill the gap for spot heating and air movement where running a full system makes no sense.

Sizing: Right Beats Big, Every Time

This is where money gets wasted. Never oversize a system — it will cycle on and off frequently, leading to higher bills, poor humidity control, and premature failure. An oversized unit feels like it’s working hard but never settles into the steady run that actually controls a room.

Capacity gets measured two ways. Heat is rated in BTUs, and cooling is measured in tons, where one ton equals 12,000 BTUs. To land on the right number, use a professional Manual J load calculation, because local climate and insulation levels are critical factors. That last part matters more here than in most places — a tight, well-insulated home and a drafty one of the same square footage need very different equipment.

There’s also a smart way to cut load instead of adding capacity. Electric baseboard heaters are zonal heaters controlled by thermostats in each room, making them well suited to zone heating — heating the occupied rooms while letting unoccupied areas stay cooler. Zone heating can produce energy savings of more than 20% compared to heating the whole area of a house. One caution for cold-climate homes: the cooler parts of the house still need to be heated well above freezing to avoid freezing pipes.

Heat Pumps vs. Electric Resistance vs. AC-with-Heat in the Cold

This is the part Montana buyers most need to hear, because the standard advice falls apart below a certain temperature.

Start with efficiency. Electric resistance heating is 100% efficient at the unit — all the incoming electric energy becomes heat — but because most electricity is generated from coal, gas, or oil at roughly 30% conversion, and because of transmission losses, electric heat often costs more than combustion heat. If electricity is the only option, heat pumps are preferable in most climates because they easily cut electricity use by 50% compared with electric resistance heating.

But heat pumps and AC heating have a temperature wall. When the temperature drops below minus 10 degrees Celsius (about 14°F), the efficiency of an air conditioner gets very low, and below that point an electric heater becomes the better choice. Modern equipment buys some room — even an old air conditioner can beat electric heating, and today’s R32 variable-frequency units achieve acceptable performance even below minus 5 degrees Celsius — but Montana winters routinely drop well past that threshold. The practical takeaway: a heat pump or AC-with-heat is best treated as a supplement, with electric resistance or another heat source standing by for deep cold.

Be especially careful with all-in-one electric AC-with-heat combo systems. The manufacturers themselves point where these belong: electric furnaces are used almost exclusively as heaters in extremely mild southern climates such as south Florida and south Texas where heating demand is very limited, and in other parts of the country you may want to consider more efficient heating options. That’s a clear flag against leaning on one as a primary heat source up here.

Two cases still favor electric resistance regardless of climate. Bathrooms, where air conditioning generally isn’t installed and overhead electric heaters do the job, and the deep-cold conditions already covered. Electric resistance heating can also make sense for a home addition when it isn’t practical to extend the existing heating system to the new space.

Efficiency Ratings and Operating Cost

Before comparing models or contractor bids, know the numbers. Ask about energy efficiency ratings — SEER2 for cooling and HSPF2 for heat pumps — because higher ratings reduce long-term operating costs. For reference on what’s on the market, AC efficiency on residential central electric-heat-and-AC systems ranges from 13 to 19 SEER, with product examples landing in the 14.5 to 16.5 SEER2 range. It’s also worth getting multiple written bids from contractors rather than going with the first quote.

Sizing Up Larger Spaces — Shops, Garages, and Warehouses

For a shop, garage, or mechanical room where running gas lines isn’t practical, electric unit heaters cover a wide range. The Modine HER series is one example: an all-electric horizontal unit heater for commercial, industrial, and institutional environments — warehouses, workshops, stairwells, and mechanical rooms — with no gas or venting required. The capacity spread shows how to scale to the space:

Model	Output	BTU
HER 30	3 kW	10,200
HER 50	5 kW	17,100
HER 75	7.5 kW	25,600
HER 100	10 kW	34,100
HER 125	12.5 kW	42,700
HER 150	15 kW	51,200
HER 200	20 kW	68,200
HER 250	25 kW	85,300

There’s a placement principle worth borrowing for any perimeter heating job. Units like this are typically placed around the perimeter of the building, letting the air stream from each heater “wipe” the wall and produce a blanket of warm air along the outside walls, where heat loss is greatest. That’s the same logic behind putting baseboard heat under windows.

Installation, Controls, and Electrical Basics

Placement and wiring aren’t afterthoughts. For baseboard heat, install under windows so the rising warm air counters the falling cool air off cold glass, and keep them on perimeter walls — interior walls are rarely used because standard practice is to supply heat where the greatest heat loss occurs. Set baseboard units at least three-quarters of an inch above the floor or carpet so cooler floor air can flow up through the fins.

Thermostat choice affects how well the whole thing works. Baseboard heaters often use a line-voltage thermostat that directly controls power, while other devices use low-voltage thermostats that switch through a relay. Built-in line-voltage thermostats often don’t sense room temperature accurately — a remote line-voltage or low-voltage thermostat on an interior wall reads the room better.

On the cooling and refrigeration side, the electrical work belongs to a licensed electrician, but it helps to know what’s involved. AC and refrigeration compressors use sealed “hermetic” motors — sealed because they share a housing with the compressor and run in refrigerant — so their cooling and electrical characteristics differ from ordinary motors. The manufacturer does much of the homework for you: hermetic-system makers supply the correct protection, conductor sizing, and other information right on the equipment nameplate, and that’s what to wire from.

The sizing rules behind that nameplate, in short: branch-circuit conductors to a single motor compressor must carry at least 125% of the rated-load current, with short-circuit and ground-fault protection sized between 175% and 225% of that rated-load current. For a plug-in room unit, the disconnect can be simpler — an attachment plug and receptacle can serve as the disconnecting means for a room air conditioner, as long as the manual controls are readily accessible within 6 feet of the floor or a readily accessible disconnect is within sight. Watch the cord length too: a flexible cord supplying a room air conditioner can’t exceed 10 feet for 120V units or 6 feet for 208V or 240V units.

A Word on Filters

Whatever forced-air equipment ends up in the house, maintenance is not optional. A built-in limit controller prevents overheating and may shut a furnace off if the blower fails or a dirty filter blocks airflow. In wood-heat country, where particulates load filters faster, this is a monthly check during heating season — neglect it and the system fights itself.

Frequently Asked Questions

What’s the difference between a ton and a BTU? They measure the same thing from two directions. Heat output is rated in BTUs, and cooling capacity is measured in tons, where one ton equals 12,000 BTUs.

Why shouldn’t I just buy the biggest unit to be safe? Bigger is the wrong instinct. An oversized system cycles on and off frequently, which raises bills, worsens humidity control, and causes premature failure. The fix is a proper load calculation, not extra capacity.

Will a heat pump handle a Montana winter on its own? Treat it as a supplement, not the whole answer. Below about minus 10 degrees Celsius (roughly 14°F), an air conditioner or heat pump’s heating efficiency drops sharply, and an electric heater becomes the better choice. Montana regularly hits temperatures past that point, so plan a backup heat source for deep cold.

Is electric resistance heat really 100% efficient? At the unit, yes — but that’s not the full picture. All the incoming electric energy converts to heat, but because most electricity is generated at about 30% efficiency and loses more in transmission, electric heat often costs more to run than combustion heat.

What ratings should I compare between models? Look at SEER2 for cooling and HSPF2 for heat pumps — higher ratings mean lower long-term operating costs. And get more than one written bid before committing.

Can I install a window air conditioner myself? The plug-in connection is straightforward, but mind the limits. The controls need to be readily accessible within 6 feet of the floor or a disconnect within sight, and the cord can’t exceed 10 feet on 120V units or 6 feet on 208V/240V units. Hardwired equipment is electrician territory.

Where should baseboard heaters go? Under windows, on perimeter walls — the rising warm air counters cold falling off the glass, and that’s where heat loss is greatest. Keep them at least three-quarters of an inch above the floor or carpet.