Ask neighbors or your contractor for HVAC referrals. There are honest ones out there but I understand they're all busy right now.

I'm wondering about your heat pump query. Heat pumps use a lot of electricity. PG+E baseline amounts, even with the added amounts for having primarily electric heating, are not very generous. And if you're near the coast and in the fog zone, I'm wondering just how much power production you can count on having from your solar cells.

The penalty rates that apply for electricity when you blow through the lower tier baseline quantities are a much higher percentage increase than is the case for gas. Put another way, using more gas doesn't cost you proportionally as much extra as electricity does.

I'd stick with gas heating but be sure a proper load calc is done - the existing furnace you have has likely been too large for our mild climate. Be sure to have your existing ducts sealed as best can be done and also beef up your ceiling/attic insulation as much as you can. That pays off no matter what.

I too am a Bay Area resident and got quite an education when replacing my equipment three years ago.

Good luck.

I would think your furnace is over sized of you your house and location. If you did switch to a heat pump it would need to be sized for cooling and not heating. But if really only use the AC 4-5 times a year you could be in an over size it for cooling.

You need to post your gas and electric rates to determine if a gas vs heat pump makes financial sense. If can sell excess electricity to the utility company then you would factor that into the cost equation. Will you be generating solar credits and have the ability to sell them on the open market?

We get great sun where I live but it does dip into 40s (and high 30s in the winter) quite often so heating power is definitely necessary.

In terms of solar we get net metering so we get to offset summer over-production vs winter net consumption. However whatever surplus is left over at year-end is compensated at only a fraction of the cost. So essentially it doesn’t make sense to over-produce. In May I am getting about 20kw per day in surplus production so I feel like that should go pretty far in offsetting electrical heat pump usage during our relative short einters

Yes, I know weather patterns but not in your unstated location. The coast can be cool and foggy well into what are "summer months" inland and in other places as you well know. It sounds like you're not in that coastal of a location. If in a place like Pacifica or Half Moon Bay, as examples, I can't imagine solar production would be that useful unless you were up out of the fog zone.

Did you choose the size of the solar install expecting to get a heat pump or to charge an electric car?

We are in tiburon and definitely sized the solar with the expectation of additional loads. We can also add more solar down the line if we get electric car etc

Ok so that's really Bayside rather than Oceanside, sunnier and more moderate.

I don't know, I personally wouldn't drift away from a gas furnace. PG+E rates for gas aren't a bargain by any means but i think you'll know with more advance certainty what you're getting into. I think your winter temps in Tiburon are warmer and more moderate than just a bit inland (in any direction, either to the north or East Bay) and away from the Bay so it's all relative.

Good luck.

Not to overdo my comments (as a fellow homeowner, not a pro) but maybe there's a halfway measure for you - install a heat pump instead of an AC unit, along with a new matching furnace. If the cost and heating ability of the heat pump turn out to be unsatisfactory for you, switch off the heat function and stick to the furnace.

As soon as you mention the words "dual fuel" contractors start thinking "ca-ching, ca-ching"! I'd stick with a hi-eff gas furnace (sized after a detailed heating load calculation) and a 14 SEER AC unit (based on your minimal usage).

You can't make a good decision without knowing the cost of your fuels. The gas utility already exists, so the gas furnace and heat pump combination would be a safe strategy if the upgrade cost from an AC only condenser is reasonable. Get quotes for both configurations.

I think installing a 60K or 80K 95% efficiency gas furnace is going to produce some savings. You should calculate your heating costs to get an idea on how much the savings could be.

At a discount rate of 5%, you'd have to save $430/month for the next 10 years or $360/month for the next 15 years to justify an investment of $40K in a new heating system.

My view is that HVAC equipment is a cost, not an investment. You pay for it to have its functionality, not for a rate of return unless you talking about whether the incremental cost of a more expensive approach can be recouped. Often people choose what they want to have with the cost being a secondary consideration at best. Sometimes not at all.

Unless I misunderstood, it seems like the circumstance mentioned is that the location for the HVAC equipment is being changed, the system may need to be altered for the space being added, so why not start over and put in new equipment.

The original author stated the HVAC equipment has to be moved, and thus is asking if a dual fuel system is a viable option to address the high heating costs. Moving an old condenser is rarely successful. The probability of a leak is high.

I would not expect high heating costs given the mild winters of SF bay area. But then again wasn't it Mark Twain who said "The coldest winter I ever spent was a summer in San Francisco."

I don't think it is necessary to spend $40K to replace existing equipment especially if is going to be smaller.

@mike_home: "The original author stated the HVAC equipment has to be moved, and thus is asking if a dual fuel system is a viable option to address the high heating costs."

He provided one number, $40K. If he has numbers for relocation and dual-fuel system, he can apply the calculation to the difference between the two options to decide whether the dual-fuel system is worth the investment.

OP lives in TIburon, not in San Francisco. The Bay Area is a world of microclimates and it can vary significantly over short distances. While Candlestick Park (on the Bay) was a chilly and windy place for summer baseball games because it's open to the ocean through a gap in the coastal hills, Oracle Park (chosen for both location and better weather) is much warmer.

I just checked - right now Tiburon is 11 degrees warmer than downtown SF. It's less than 10 miles away, and mostly across open waters of the Bay itself. But the Bay is warmer than the ocean (shallow water) and Tiburon is more shielded from the westerly winds that bring in cool air and fog off the ocean this time of year.

San Francisco's weather is cool and foggy now and remains so until later in the summer. Drive out of town 5 miles or less in any direction and it will always be warmer and the farther you drive, the much more so. Remember, less than one hour to the north is the wine country, which is roasting hot in the summer. So too the inland East Bay, just east of the hills just across the Bay.

(I think we've had this conversation before?)

Thank you all for the feedback. Agree on many of your points. Since I am paying the labor to move equipment and replace a lot of the duct work, it seems that now would be the time to upgrade if I choose to do so. My options boil down to the following:

5ton heat pump - likely most economical long term due to solar but potentially underpowered as a heater (60k btu)

Gas heater - move current or replace with more efficient unit. Cheapest option up front but likely the most expensive option in terms of running costs

Dual fuel, probably an additional $3000 in equipment and labor vs heat pump but theoretically gives me the economy of a heat pump and gas heating as a reserve for those really cold nights.

Did you get a quote for $40K+ or is this a number someone gave you over the phone? Have you figured out what are your gas and electric rates, and how much do you get for excess electricity generation?

I have several quotes in the high 30s
Gas cost 1.62/therm below baseline 2.10 after that (winter months bulk of my usage is above baseline)
Electrical cost is ~30c in the winter above baseline.

In April I net produced 660kw so approx 20kw production/day during summer months

I know many people with solar panels. It's a smart thing to do, it's the future. As I think about it, about half of them drive electric cars. None of them has mentioned switching home heating to heat pumps. Other than for folks in municipal or community power purchase regions, our electricity rates are high compared to US averages. Gas is too but still seems to be the energy of choice preferred for heating in our area.

Because you're in a relatively mild weather area, if your home is reasonably well insulated, a 5 ton unit producing 60K BTUs would likely keep your home warm during much of the heating season. Having a gas furnace in reserve when you need a bit more oomph or a warmup from a setback will be useful. I wouldn't want to pay the electricity bill to pay for that or pay for enough solar cells that would be needed.

On reflection I'm puzzled by your comment that "we are consistently getting into the upper ($$$) tiers on our gas bill.". There's only two tiers for gas, so just one upper one, but honestly, other than folks who use no heat or keep their homes very cold, I think everyone is in the upper tier because the baseline amount isn't much. To put it in context, my house is about 1/3 larger than yours and I don't think I pay as much as $700 per year for heating. So assuming I could pay nothing at all by using solar panels and heat pumps, how much would I have to spend for that extra equipment and how long would the payback period be? I don't think the dollars and cents work. Your situation can't be very different from mine unless you keep your house very warm when it's cool outside (we heat to 68 but have an 8 degree setback at night and during the day) . The incremental solar panels and heat pumps you'd need to sustain a constantly warm home would ramp up similarly.

The people I've heard of who have massive solar panels and a lot of heat pumps (for large homes) have done so for ecological/ethical/pseudo-political reasons. Such folks have the money to spend and have done what they've done knowing there's a large incremental cost and no payback. They do it because it's what they want to do.

"In April I net produced 660kw so approx 20kw production/day during summer months"

I think your numbers are off and check what you're describing - kilowatts or kilowatt hours. . From what I know, residential panel installs tend to run in the 5-7 kW range. (That number is determined by the production of each panel X the number of panels). That produces about 10K kWh per year. Aside from places with months-long 24x 7 AC or heat pump usage or very large houses, most homes use 500-1000 kWh per month.

My AC equipment consumes a bit more than 1 kWh per ton, when on continuously. Figure how many hours per month the heat pump would run to estimate the incremental electricity use.

Here are some numbers as you consider a dual fuel system:

Approximate cost for 100K BTU of heat:

Gas furnace 95% AFUE @ $1.60/therm = $16.84

Gas furnace 95% AFUE @ $2.10/therm = $22.11

Heat pump 3.0 COP @ $0.30/KWh = $29.31

Heat pump 2.5 COP @ $0.30/KWh = $35.17

Resistive heat coil @ $0.30/KWh = $89.92

Using these rates the gas furnace will be cheaper to operate at most outdoor temperatures. However if create excess electricity during the heating months then the heat pump would have the advantage.

You are right - I was referencing kWh. Most of the systems I am looking at are seer 18 which I believe is COP of 4

COP (coefficient of performance) changes as the outdoor temperature drops. It is not related to SEER which as a measure of cooling efficiency. The heat pump may have a COP of 4 at 50 degrees but it will be less at 25 degrees. If you have a model number the performance data can be researched.

"As soon as you mention the words "dual fuel" contractors start thinking "ca-ching, ca-ching"! I'd stick with a hi-eff gas furnace (sized after a detailed heating load calculation) and a 14 SEER AC unit (based on your minimal usage).

Nonsense, the cost differential between a HP and and an A/C plant of equal capacity is very small !"

Cool. Go install a dual fuel system for this guy!

We both know a heat pump is just an AC with a reversing valve (OK, and a defrost board) but that doesn't stop AC contractors ripping you off when they hear those magic words.

"if create excess electricity during the heating months then the heat pump would have the advantage."

The true up or reconciliation of production versus use is done on an annual basis in California, or at least, it has been in recent years. If someone is producing excess electricity in Tiburon during heating months, their solar installation is oversized and they were overcharged. Solar installers are careful not to oversell their installs because it's generally uneconomic to sell back excess production. A figure I've heard is that they target production to not exceed 90% of a customer's expected usage, based on past history and expected increments (like getting an electric car). Or, that may have just been the practice of the contractor my friend recently used.

Remember that Tiburon weather is very mild and is neither an AC intensive nor heat intensive use area compared most of the rest of the country. Even compared to most of the rest of California in certain respects.

"it will be less at 25 degrees"

Haha, I doubt it has ever been 25 degrees in Tiburon. Not ever. Wintertime lows average in the 40s, to set your expectations.

I found Tiburon on the map. A very nice location surrounded by water. I found out the all time record low has been 27 F degrees. The current 120K BTU furnace is very oversized.

"Now you've gone fully moronic. I'm not an installer, why would you suggest that I install a system for the OP? That's as ridiculous as me suggesting that YOU make a thoughtful, helpful post that adds value to the thread!"

Like that one?

So in theory could I just get away with the 5 ton heat pump and call it a day?