Pros and Cons of Ductless Mini-Splits VS Direct Vent Gas Wall Heaters?
January 27, 2017 7:50 AM   Subscribe

Due to a crack in my steam boiler, I now urgently have to revamp the heating system in my new-to-me 19th-century rowhouse. I have been researching for the past couple months in order to optimize the heating in my house. I am not interested in salvaging the steam heating system. I have basically narrowed down my options to:

(1) ductless minisplits (my house does not have central air, so that would be a big plus of this option)
(2) Direct Vent natural gas wall heaters on exterior walls (pretty sold on the Rinnai ones).

I'd love personal or professional opinions on the pros and cons of each option, especially including installation costs, operating costs, efficiency, comfort, reliability and maintenance costs, ease of use, appeal to future tenants/homebuyers, etc. Any recommended brands/models? Halp?!
posted by ClaireBear to Home & Garden (7 answers total) 1 user marked this as a favorite
Minisplits are much more efficient than natural gas wall heaters. Operating cost depends on your relative cost of natural gas versus electricity. Climate impacts for minisplits are likely lower.

Minisplits will be easier to place where you want as you can run the refrigerant lines some distance, while the gas heaters need to have a vent right behind them.

Gas heaters will heat faster. Minisplits will be much quieter.

I would definitely prefer minisplits as a buyer.
posted by ssg at 8:24 AM on January 27, 2017 [1 favorite]

Mitsubishi and Fujitsu are the brands that people tend to use in climates where it can get cold.
posted by ssg at 8:25 AM on January 27, 2017 [1 favorite]

This may be a difficult question to answer without knowing what the climate is like in your location.

I've installed a couple of mini-split systems and I like them. They're great in areas that you can't imagine running gas lines, and crucially they provide both heating and cooling so they're handy all year round. The heating is efficient, so even if your electrical rates are a little higher than your gas rates, they'll probably save you a little money in the end.

However, they can't generate a whole lot of heat all at once. They can keep a room warm, but if there's a sudden cold spell, it can take a while to make it all the way to the kind of warmth you would get in minutes from a gas heater.

If you live in a place where winters are mild, short, or don't have sudden swings in temperature, mini-splits are great. If you live in a place where it can drop 40 degrees overnight or there's endless below-zero weather, you might want to go with the gas heaters.
posted by eschatfische at 8:29 AM on January 27, 2017

Thanks for the input so far, guys! Really helpful!

Just to provide some clarification: I'm in Philadelphia, so the weather is reasonably mild. The house is around 1200 ft2, so not too large: each floor of my house is about 400 ft2. The insulation is fairly poor, since it's an older house, but it only has exterior walls on two sides (and other houses on the other two sides). I forgot to mention that I'm also in the process of installing some pretty efficient direct vent gas fireplace inserts. There will be one on each floor in the old masonry fireplace, they will provide up to 40,000 BTUs of heat each (on a thermostat), and they are up to around 85% efficient.
posted by ClaireBear at 8:39 AM on January 27, 2017

I'm in Philly too, similar size rowhouse. Our setup is a new high-efficiency boiler attached to baseboard radiators, with mini-splits for cooling. I just realized this winter that I can use the mini-splits as ersatz space heaters (more efficient though) when the whole house doesn't need to be warmed (bedroom at night, office when WFHing). Works well. Sounds like your fireplace inserts should accomplish something similar to our radiator heat. I'm not sure if I'd rely on the mini-splits alone for whole-house eating-- they're definitely more localized in effect.
posted by supercres at 1:10 PM on January 27, 2017

I lived in Philly way back when in a studio with a split. Knowing you're installing the gas inserts, I'd definitely take the splits in this scenario - IMO, the occasional "these are taking a while to warm up" in the winter will be totally offset by the benefits of the cooling functionality in the summer.
posted by eschatfische at 5:36 AM on January 28, 2017

Thanks for the very helpful advice, all! For anyone reading this question in the future, I decided to update with the choice that I made here, as well as my reasoning. I decided to go with the mini-splits for a few reasons:

(1) They also provide cooling: since I don't have central air, this is killing two birds with one stone.
(2) They diversify my heating sources: the mini-splits run on electricity and my fireplace inserts run on natural gas. This will help me hedge against future unpredictable rises in the cost of either heating source, as I can then more heavily rely on the other.
(3) I may be able to get solar panels on my roof or on my roof deck in the future, which would allow me to provide my own electricity to power the mini-splits, significantly reducing my energy costs.
(4) As power plants become more green, it's possible that electricity in my area in the future will be generated increasingly by green sources rather than by fossil fuels. Having the mini-splits that run on electricity will allow me to rely on that if and when that day comes. Even right now, I have the option to buy electricity from a private company that uses some green sources and that works in tandem with my area electric company for billing.
(5) Because they are heat pumps, the mini-splits are especially efficient in mild temperatures (above freezing), when heat outside is easier to find. This will allow me to rely on them solely in the shoulder seasons (spring and autumn) when they are most efficient, and turn on my powerful gas fireplace inserts in the winter.
(6) Mini-splits seem popular right now as an efficient and green source of heat. I think that they will improve the value of my home to future buyers and renters.

The major downsides appear to be:

(1) Cost. I had about 12 HVAC contractors in to give estimates, and they were all over the map. The cheapest estimates were about $3500-4000 for a Mitsubishi Hyperheat (either 9000 or 12000 BTU) installed, and I will need several of these. Some of the estimates were about 50% higher (!) so I would strongly recommend getting multiple estimates: it seems that the pricing is highly variable. Make sure that you're comparing like with like, as well. I had the option of a generic brand for a bit cheaper, but I decided to go with Mitsubishi, which is apparently top of the line. Since labor is at least 50% of the cost and the labor cost is the same regardless of the machine brand, I didn't want to save maybe 10% and have a less reliable product. I also decided to go with a Mitsubishi diamond dealer, as they have a longer warranty and supposedly better access to preferred customer service. They were also two of the cheapest bids, oddly enough.
(2) Can't rely on them as sole source of heat. As the temperature drops, heat pumps become less efficient and also capable of producing fewer BTUs/hour - just when you need more heat! They stop working once the outside temperature drops to a certain level. Therefore you effectively need a reliable back-up form of heat capable of heating your entire house for the rare extremely cold days. This won't be a problem for me, since I was already planning on installing powerful direct-vent fireplace inserts, but might be a concern for someone else, since obviously having to create a 100% redundancy in your heating system design adds significantly to the cost. While the efficiency of normal mini-splits begins dropping below about freezing, there are cold climate ones that stay very efficient at far lower temperatures. I'm paying $375 extra per machine to upgrade to Mitsubishi's Hyperheat line for just this reason.
(3) According to my research, in my climate zone it requires less energy to cool than to heat. In other words, you have to get a larger mini-split in order to handle your heating requirements, if you hope for it to be able to handle your house's heating, than you actually will need in the summer for cooling power. Apparently, unlike typical furnaces and boilers, mini-splits actually are most efficient when working at partial load (i.e. oversizing rather than undersizing) - as long as your heating or cooling requirements on a mild day do not drip below the minimum modulation of the unit, which would cause it to cycle on and off (i.e. if the mini-split can modulate down to 2800 BTU/hour and your requirements on a 50F degree day are lower than that, you may get cycling and inefficiency). The downside is that it's really hard to find out these numbers.
(4) They work best when you have a very open floor-plan with a lot of ability for air to move. I am not convinced that they will be optimal in places like the upstairs with bedroom doors shut. We will see.
posted by ClaireBear at 7:51 AM on February 5, 2017

« Older Need help comparing/contrasting high end CPUs   |   Diary app for boring details of daily life Newer »
This thread is closed to new comments.