artemis

what size is existing furnace?

what is your location?

what are you doing about AC?

The smallest two stg furnaces are 60 KBTUs with about 38 KBTU for low stg, 56 KBTU on high stg. I doubt you would ever need or use the high stg.

Based on your description of your climate, I think a high eff Heat Pump is worthy of consideration if you have reasonable electric rate.

IMO

Thanks tigerdunes. We're in Northern California, where it rarely tops 80, so we don't have air conditioning. Our current furnace is 70 KBTU to heat 1000 square feet. (One room is not currently heated; we're adding ducts there so the new furnace will heat 1250 square feet.) When I've used furnace size calculators and such, they typically suggest much smaller furnaces---in the 30-50 KBTU range.

Thanks!

artemis

if you are just looking for a quality furnace without bells/whistles that qualifies for tax credit, take a look at Trane's XR95 or sister company model from American Std.

38 KBTUs with a two ton rated blower if you wanted to add AC at a later date.

XR95
TUH1B040A9241A 40 17.5 28 38,000 95

of course the small XV95 60K two stg var speed furnace is nicer but with a price.

link attached below.

IMO

Here is a link that might be useful: XR95

I would most definetly recommend 2 stage.
In those kind of mild climates, the hi-stage of a single stage or 2 stage furnace will end up having a very short run time. It will end up leaving things unevenly heated.

You would be better served running the low stage of a 2 stage furnace. To be honest, even thats alot of heat. If your lowest temp is 40 deg F. You should consider a heatpump. I know california has high electric rates but you don't need alot of heat if your lowest temp is 40 F. It won't be running much. This is also when heatpumps put out their most heat and are extremely efficient and make comfy heat.

What does electric cost per KW where you live?

What type of gas bills have you had?

neoheatpump - he lives in N CA in 1000 sq feet - do you really think a 2 stage furnace makes sense?

OP - Your heat load is hard to determine because you may have zero insulation and a window open all the time. Probably not but impossible to say without more info.

Since your heat load is hard to determine, it is hard to say if you can even have a 2 stage furnace that makes sense. I know around here, when it is 60 degrees out, I don't need heat. In most cold climates, you don't need heat at that outside temp. Solar and internal heat gains give you well over 10 degrees in an insulated, tight house.

I'll guess that you have a leaky older house. Your best bang for your buck is to tighten the house.

A 95% furnace is overkill for your climate and size house. I would guesstimate that for your situation, you'd probably need $200 a year in gas. A 95% furnace might save you $10 a year over a 90 and $30 over a 80. Very hard to get that to pay off when you pay $1000 extra for it (or more). If you need more gas than that for heat, then you would be better off insulating the house better.

My political rant here is that CA is so stupid sometimes. You would do better for the environment by having a heat pump. It would be more efficient in every way than using NG to heat in a mild climate. But you have tiered electric rates that discourage your best option. All they have to do is relax the tier in the winter for heat pumps. Lots of places have lower electric rates for homes with heat pumps - around here we just have lower electric rates in the winter (to encourage heat pumps).

Rant off - if you stay in lower electric rates, a heat pump will be cheaper to run. With the typical $.10 a kwh and $1 a therm, at mild temps a heat pump will be half the cost of NG or less. It will cost more however and may not pay off but is a better deal than a 95% furnace (compared to your most cost effective 80% or 90%).

Rant back on - does CA mandate 95% furnaces? It would be far more effective to outlaw SUVs or mandate hybrids....

it should be said that heat pumps are not practical for California unless homeowner does not have access to natural gas.

80% furnaces should be adequate based on California climate and nat gas rates. however with the tax credit, a homeowner should go ahead and take the 95% furnace as long as it's sized correctly.

while I do like the two stg 95% VS furnaces, it is doubtful second stage would ever be required. kind of like paying for something you don't need or will ever/rarely use.

IMO

Thanks---yes, California does still allow 80% furnaces, but offers heavy incentives for the 95% efficient furnaces such that the cost difference is negligible. In our case, the single biggest reason we'd go with 95% is that we can vent it horizontally v. vertically, and our current vertical venting setup is not to code, so we're looking at a lot of money spent just to re-vent our existing 80% unit. (We're replacing the furnace as part of a kitchen remodel that's knocking out the old vent chimney. We'd planned to just keep the current furnace, since it still works fine, but have hit issues with the status quo venting---we were just going to put the vents into the wall---being against current code. It seems to be cheaper to buy a new one, so we're leaning that direction since the current unit is 18 years old so could be seen as a liability when we sell in 5-7 years anyway...)

I'm not familiar with heat pumps, so I'll look into them---but we do have the tiered electric rates, which could be an issue. We're eventually hoping to put in solar which could negate that, but now that PACE programs are all on hold (our city was supposed to be one of the pilot sites), looks like no time soon!

@david_cary, we do indeed have a leaky older house. :) Working on tightening it so it has some insulation (attic, a few walls, weatherproofing) and we don't leave windows open or anything, but far from air-tight. We probably spend $200-300/year on heating, I'd say.

Thanks for all of the thoughts!

Ok Tigerdunes - why would a heatpump not be practical in CA? High electric rates? I could see someone in a small house never bumping into the higher tiers even with a heat pump. Throw in solar and it becomes even more viable.

Higher capital cost - absolutely. But if you are considering a 95% furnace with venting issues - that might get expensive too.

OP - heat pumps are just a/c running in reverse. A very efficient way to heat a house especially above freezing temps. But at $300 a year - hard to argue with the cheapest NG furnace you can get. But you will never be able to make NG from the sun....

Okay, so this turns out to be super interesting!

As it turns out, California does have separate "baseline" electric rates for homes with electric heat, and does have separate winter and summer rates as well. (I've never paid attention to either of these as they've not affected us one way or the other in the past.) I'll need to find out if we can use our existing vents for a heat pump, though, as that would be a big factor.

In winter with a heat pump, we get 20.2 kWh/day as our baseline. I'm not sure how much a heat pump would actually use, but we currently use about 6 kWh/day, so we'd have a good bit of wiggle room. Right now, the next tier (101-130% over baseline) is priced almost the same anyway, though.

Good to know either way! :)

If you are only using 6 kw per day. And you can use up to 20 kw per day with the same rate on electricity if you get a heatpump, you would be fine. You could run the heatpump for a good number of hours per day assuming you got a 2 ton heatpump. Sounds like heatpump is very practical for your situation although it would have a higher upfront cost.

Thanks all. As it turns out, the cost of the heat pump is prohibitive for us, so that's out.

Any thoughts on Amana's two-stage furnace, which one contractor recommended? I believe it's AMVC95 0453BX---runs at 45kBTU on the high stage and 30kBTU on the low stage.

that sounds like that would work good for you. It will probably never go out of the low stage. That is better than having a single stage with only the option of 45k.