What's the Most Budget-Friendly HVAC for a Massachusetts ADU?

By Buz Artiano, BuildX | February 2026

We have seen a lot of HVAC systems go into ADUs over time, and we know what happens when homeowners try to save money with cheap equipment, and it never works out well. When it's below freezing one night and that circuit board burns out and there are no parts available, not only are you left in the cold, but you are looking at a complete system replacement. It's not worth the $2,500 you saved up front.

This being said, we understand that cost still matters. Building an ADU is not a small investment, and every dollar matters. The question of heat pumps versus gas is one we answer almost daily, and the answer might surprise you: gas is not always the cheaper route.

At BuildX we build ADUs across Massachusetts, and we have fine tuned our methods when it comes to HVAC systems. We base our recommendations on real-world performance, not manufacturer claims. When we build an ADU, we look for the most budget-friendly, good quality materials we can get to make sure the ADU is going to last and have zero issues. This is especially important when it comes to HVAC stuff, because cheap equipment creates expensive problems.

Why Are Heat Pumps the Budget-Friendly Choice?

HVAC prices for ADUs are usually between $8,000 and $25,000 depending on the system type, brand, and whether you choose ducted or ductless. Gas systems are at the higher end of that range because of the boiler you need and extra infrastructure costs. Heat pumps with wall-mounted mini splits are much cheaper while still providing both efficient heating and cooling.

Heat pump systems are going to be your best bang for your buck for an ADU. The math is pretty simple: adding gas service requires running gas pipes and installing a boiler, which adds a lot more to the final cost. Even if you already have propane or natural gas on your property, the infrastructure cost to pipe it into an ADU and install the proper boiler system still makes it much more expensive than a heat pump system.

If you want a gas stove or gas dryer, we recommend running gas only for those specific appliances and still keeping the HVAC as a heat pump to save money. There is quite the price increase to go from a heat pump system to a gas-fired boiler, but if you separate your cooking from your heating and cooling it keeps the price manageable.

What Will Gas Heat Cost You?

Well, we already know that there's a much higher installation cost. But did you know that gas-fired hot air systems produce dry heat? You get a high heat hitting an air exchanger that produces very dry air into the house. We hear people complain about this all the time, saying "My house is too dry." With a heat pump, you do not get that dry desert air feeling because the system runs slow, maintaining comfortable humidity levels regardless of how much you run the heat.

Heat pumps also provide cooling in summer using the same equipment, unlike a gas furnace that only handles heating. For a small ADU, having one system that does both is so much more cost-effective than installing two completely separate systems.

Should You Choose Ducted or Wall-Mounted Mini Splits?

This is where you have a little financial room to play with. If your budget is tight, we can save about $5,000 by using wall-mounted mini splits instead of a ducted system. Both use the same heat pump technology, but a mini split is more visible and requires a bit more maintenance.

Ducted Systems

With a ducted system, you have what's called a central air handler (a unit that usually goes in the crawl space) connected to ductwork. There are vents in the ceiling or floor, just like a regular HVAC system. The technology of a traditional HVAC system and a mini split are exactly the same, but with a ducted system the air handler and ductwork are all hidden. It's the same technology, only instead of heads on the walls, it's all tucked neatly inside an air handler with duct work.

Wall-Mounted Mini Splits

Wall-mounted mini splits have visible heads on the interior walls. They work great, but they require annual cleaning. The fan on the inside unit gets dirty, and you can see black mold build up if you look inside. This is not a defect; it is just the nature of wall-mounted units. If you want to go with a mini split, you just have to factor in the maintenance they require.

If you get up against the budget, going to wall-mounted mini splits is a legitimate way to save some money. But keep in mind that you will be trading some convenience for cost savings. You are not sacrificing quality as long as you go with a reputable brand.

Why Does the Brand Matter So Much?

We refuse to buy cheap stuff. We will not compromise on that, it's just not worth it. We use LG, Mitsubishi, and Cooper Hunter. As long as it is a name brand and we can make sure we can get parts, we are willing to talk about it with you. But unless it says LG or Mitsubishi or another large brand name on it, you risk having equipment that can't be fixed, only replaced completely.

Here is what happens with cheap equipment: People think they are getting a deal by buying a Doosan or some other off-brand thing at a cheap price. Two huge problems right off the bat. First, these systems do not work when it gets down to minus 15 degrees like it can at night and with wind chill. They are only rated for down to 5 or 10 degrees. So in a real cold Massachusetts winter, you cannot heat your house, period. And the second huge issue is that when the circuit board burns out, there are no parts to be found anywhere. You saved $2,000 or $2,500 upfront, but that is going to 100% come back and bite you.

The way heat pumps work, the outside head and the inside coil are married by the manufacturer. Most people don't know this, but if the outside head fails and you can't get parts to fix it, you have to rip out the inside part as well and replace everything. Those cheap units never fail unless it is really cold out or really hot out, and they always fail on a Saturday afternoon when no one is available to fix them.

Do Heat Pumps Work in Cold Massachusetts Winters?

Name-brand cold climate heat pumps are rated down to minus 15 or 20 degrees. The newer models go even lower, some down to minus 35 degrees. The units we use also have electric backup, so if the unit fails, no emergency, you still have heat.

Which is another reason brand matters. Reminder: Off-brand heat pumps only work down to 5 or 10 degrees. In a Massachusetts winter, that is not going to cut it, it gets colder than that here as you know. When we spec equipment, we are looking at Mitsubishi, LG, Carrier, and similar manufacturers that offer real cold climate performance and easily replaceable parts.

What Are the Real Energy Costs?

Heat pump systems nowadays are very efficient. Here are actual numbers from our Massachusetts ADU projects:

A 900-square-foot ADU we finished in Plymouth has three people living in it. Everything is electric. The highest electric bill they have ever had in the summer was $225. We have another client whose electric bill last month was $175, and that was for everything. We have a third project with three people living in it that runs about $250 monthly average for all-electric utilities.

These are real numbers from actual bills of people who live in ADUs, not some manufacturer estimates. Heat pumps have really transformed what is possible with all-electric construction.

How Should You Operate a Heat Pump System?

The secret to a heat pump system is to set a temp and then leave it alone. Just let it do its thing. Heat pumps like to run low and slow. They use way more energy to heat a house that has been turned down to a colder temperature.

Years ago, you would leave for the weekend and turn the thermostat down to 55. When you come home, the house is freezing, so you just crank the thermostat up to 68, and an hour later the house was warm. Heat pumps do not work like that. If you turn your heat pump down and come home to a cold house, it will take hours to get it back up to temperature.

With heat pump systems, they are on all the time running low and slow. The most important thing to remember is to set the thermostat, and leave it alone. If you go out, do not turn it down or up. Figure out the temperature you want and just leave it there.

When Might Gas Make Sense?

Since most of the systems we install in our ADUs are heat pumps, you might think that's the only option we recommend, but heat pumps are not right for every situation.

We recommend everyone take a serious look at a heat pump system first. However, if you are someone who says, "I have to have a gas stove," that is fine. If you are a cook and you are used to a gas stove, you may not want to give that up. If that's the case, it's no problem. We just run gas for the stove and keep the HVAC electric.

Fortunately the current codes allow you to have mixed fuel systems if the house is modeled correctly. So you can have gas appliances and also an electric heat pump in the same house. This way you still save money on heating and cooling, but you have your gas stove in your kitchen as well. It's the best of both worlds.

Making Your ADU HVAC Decision

For most ADU projects, a heat pump system with name-brand equipment is the cheapest and best route to go. You avoid the extra cost of gas piping and combi boilers, you get heating and cooling from the same system, and your monthly energy bills stay low.

If you want to discuss HVAC options for your specific ADU project, including whether ducted or wall-mounted makes more sense for your layout and budget, we are happy to walk through the details.