I am a plumbing and heating contractor in RI and I have done hundreds of oil to gas conversions, including at my own house.

Every situation is different and needs to be evaluated individually to determine if a conversion is best for you, and what the actual cost will be. It really requires a proper evaluation of the home, a heat loss calculation and a thorough understanding of the pros and cons by the homeowner. Then you can evaluate all the different options available to you. Gas does have less btu’s (heating capacity) than an equivalent amount of oil, but it is cleaner, prices are less volatile, the systems are generally more efficient, and you can use it for cooking, grilling and standby generators as well. Add to that the space freed up by getting rid of that nasty old oil tank.

Here are a few questions to help you along the way.

First question is Boiler (hot water baseboard or radiators) or Furnace? (forced hot air/AC)

Answering this will guide the rest of the decision making process.

What are you doing for AC? Do you have ducted AC already and adding a gas furnace for heat is simple, or are you using window units or mini splits? Can you add ducting easily? (unfinished basement and open attic space) or is that a difficult and costly proposition? There are obvious advantages to furnaces (HVAC) like central air, very high efficiency furnaces and easy maintenance. Some of the cons are ducting is bulky, space consuming, and expensive to install if not previously existing. Forced hot air also tends to be very dry and a generally less comfortable heat source.

Boilers are split into 2 categories, traditional cast iron and modern modulating and condensing. Gas fired cast iron boilers are the tried and true traditional option. They are very simple, extremely reliable, require minimal maintenance, and have a fairly long service life. The trade off is reduced efficiency, generally in the 80%-90% range. There are also no rebates on these. The other type are the modern modulating and condensing systems that are very popular. These are small, wall hung units that are extremely efficient, quiet and clean. They run in the 95%-98% efficiency range and can adjust the burn rate to match the heating demand for additional savings. They are often eligible for sizable rebates depending on the model. The downside is in longevity, and maintenance. They will require annual cleaning and due to their inherently technical nature, will not last nearly as long as the old cast iron boys. Additionally upfront installation cost will be higher.

The last wrinkle here is domestic hot water, the stuff that comes out of your showers and sinks. You have several options here that should be considered when doing a boiler swap/upgrade. You can get a combination boiler/water heater if you go the modulating/condensing route, or you can get an indirect fired w/h that uses the boiler as the heat source regardless of boiler type. Or you can go with traditional stand alone water heaters, either gas fired, electric, or electric hybrid. All having their own pros and cons.

It’s a shitload of information to take in, but it’s important to make the right choice as you will be paying for it for a loooong time.

I’m happy to help you with specific questions here or via dm if you like but I’m not taking on any new work at least till next year so I probably can’t help you beyond guidance.