# Comparing energy cost break even points

I'm trying to calculate the heat loss "breakpoints" for going all electric with heat pump, dual fuel system, or conventional gas heat. A what annual energy use points does each choice make sense? For low use customers all electric is probably the way to go, medium use could be "Plan A" + DF system, High use "Plan B" conventional system.

Winter Electric Rate: 10 cents per KWH for the first 600KWH, 6 cents per KWH thereafter.

Gas Rate "Plan A" \$13.21/mo plus \$3.73 delivery charge OR "Plan B" \$28.76/mo, no delivery charge. This is addition to the cost of gas itself which has averaged about \$5.00 per DTH recently.

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### Replies to This Discussion

Hi Bob,

I was hoping some of the more mathematically capable would jump in here with some help as I know this has been done before.  Lacking any other input I will see if I can muster up any guidelines.  Seems like this would be a good application for a batch file, called a custom app today.

Bud

That was the point of starting the discussion, to have somebody smarter than I am to crunch the numbers. Just want to see if getting a 90% furnace vs. and 80% is worthwhile, and does sizing affect monthly consumption.

In another discussion some say there is little difference between a 90% and 98% furnace, one might have a slightly larger secondary heat exchanger or be more finely tuned. Most agreed once you go to a condensing furnace it's mostly a shell game for ratings on 90% vs. 98% of real world efficiency. All capture the majority of the latent heat and have discharge air temps of about 120 degrees.

Bob, you are plenty smart enough to do your own numbers.  Here's a tool that'll save you a bunch of time. http://bit.ly/fuelbtucost

We saw decoupling of oil and propane from natural gas and electricity 6-10 years ago.  I think we will see NG and electricity stay pretty competitive against each other until export really ramps up.  At that point gas will likely be tied to world price (instead of continental price), but electricity will likely be price inelastic above the cost of self-production (solar and wind).

In other words, when gas goes down electricity will go down.  When gas goes up, electricity will follow to a point then stop.

I think the smart play is to move away from FF as quickly as possible.  Design and plan in a way that doesn't make large infrastructure investment that leaves you exposed to using a source you can not produce yourself, or you expose yourself to serious pain.

Also, if you don't consume a lot, fixed billing and meter rental are likely to make your total cost per unit not so attractive, as I think your OP nicely suggests.

I’ve seen the calculators for direct comparison, it's the "stepped rates" that are throwing me off. How to account for the 2 different base charges for each gas plan and the price break over 600KWh for electric.

That too is over my head.

I'm convinced that electric is the only future for us as individuals, for communities, and for the planet.

You run that calculator and heat pumps only need cop above 3.5 to start making even natural gas look stupid, so for climates that spend most of their heating season above freezing, the infrastructure, added monthly fees, and climate damage simply don't make sense.

Like you found, they don't make furnaces small enough for your house, and that's pre-weatherization with duct OUTSIDE the envelope!

Electric tech will continue to improve.  And weatherization will continue to show ever more amazing load drops as people learn how to do the work properly.  Seriously, my brother in law has a 1500 sf ranch with 4 occupants, and his annual gas use is 500 therms?  Nearly 1/3 of his gas cost is billing and meter rent!

Our house is about the same size with same occupant count and same use!! We were MUCH higher use this record winter, but previous years we are around 50DTH. And yes, 1/3 of the cost is meter fees!!

And I expect those fixed charges to go up as consumption continues to go down.  So eventually you'll be paying 1/2 energy, 1/2 fees that have nothing to do with consumption.

If you had switched to electric by now you would have about the same energy cost, and be saving the fixed cost.  I got rid of two gas meters last year - that's almost \$500 in found money to me!  As stoves go I'll switch to induction.  As furnaces go I'll switch to heat pumps.  As water heaters go I'll switch to electric.  Eventually I'll get rid of 2 more gas meters!

I'm leasing solar on my rental property, it has nice solar exposure.  It will also set a nice example for the neighborhood.  And it means fixed electric price.

See how this either has to be strategic or painful?  Doing it all at once would be painful.

If you decided now that your strategy is to shift to electric, how long before it happened?

As use dropped it would make more sense to switch to Plan A on the gas which cuts meter costs by over 1/2. The question is how much further use would need to drop to make the switch to all electric feasible. Then it's a question of the cost to switch everything out v.s payback in energy savings. If I were to build a new home today I’m not sure that the gas meter fees could be justified.

HUGE regional variation in energy prices.  Here in Southwest NM, residential NG currently runs \$0.655 per therm, with \$13.34 in fixed monthly costs.  Electric is currently \$0.1275 plus \$5.63 in fixed monthly costs.  All of the above include taxes.  Ignoring the fixed monthly costs, we would need to see an average seasonal COP of 5.4 to compete with the 95% mod/con boilers we typically specify.  Moving away from FF is a worthy goal, but a good chunk of our electricity here comes from coal and most of the rest from NG.  Combine that with minimal cooling loads and the ROI for heat pumps becomes a tough sell.

I think it is MUCH easier to justify incremental cost than total cost, so "switch everything out" today isn't something I'd be comfortable recommending without a LOT of detail.

So it become a question of either looking at the landscape today and assuming things will never change, or looking at how things have been changing and attempting to anticipate how they will change going forward. From there build a strategy so that as urgent replacement needs occur, thoughtless replacement isnt the rule. Instead, since advance strategic design thinking has occurred, replacement need brings opportunity.

Probably not very clearly explained, can you make heads or tails of it?

I get what you are saying. Go with a larger plan and replace the appliances as they fail. 50DTh = 14,650KWH. 14,650KWH @ 6 cents = \$879. 50DTU @ \$5.00 per DTh = \$250 + \$345 delivery fees = \$595. The calculations do NOT factor in using a heat pump instead of resistance heat.

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