Hi all,
I’m looking to reduce my electric bill.
Details
Electricity Usage
On average, I use about 1900kWh a month, with summer months being almost 3000kWh. Here’s my usage graph:
Most of this appears to be HVAC usage. I understand an HVAC should be running only about 15 minutes an hour on average, but I’m looking at closer to 30-45 minutes with my HVAC running for about 12-14 hours total a day.
House Info
(Some info from original buying inspection)
My house has 2 above ground floors and 1 below ground floor, with a total sqft between them of 2500 sqft. It is a cape cod wood-framed structure with a Bedford stone and brick veneer. The exterior walls do not seem to have insulation based on spot checks but I haven’t checked every room.
The roof is a gable design covered with asphalt/fiberglass shingles in the first half of their useful life. The attic above the living space is insulated with fiberglass batted insulation, approximately six to eight-inches in depth. Additionally, the knee walls of the attic are missing insulation.
The current HVAC system is a Trane 4TTR4036L1000AA AC Unit and TUH1B080A9421CB Furnace. There is 1 vent in the basement, 2 vents upstairs, and the rest of the vents on the main floor. The 3 return vents are on the main floor as well. Notable is that the upstairs vents are metal ducting until they hit the basement in which there’s a 8-10ft section on each that is insulated flex duct.
Previous attempts
First thing I bought was a Nest Learning Thermostat and an additional temp sensor for upstairs so I could have usage statistics.
In 2022, I started Supercooling the house. This might have reduced the electric bill more if I was on a time of day rate, but I’m on a flat rate.
This year, I patched a vent sized hole in the ductwork that was dumping all the cool air downstairs that I didn’t previously know existed and have stopped Supercooling.
Advice needed
I want to do more to reduce my HVAC and electricity usage. Currently, I’m considering the following 3 things:
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Vinyl Siding - I don’t think the exterior bricks were helpful when I was trying to supercool the house previously. I’ve been told they radiate captured heat after the sun goes down which likely wasn’t making it as easy on the HVAC.
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Insulation - An obvious choice. Although, I’d have to tear off all the existing drywall (and trim? I’ve never done this before). This will be a lot of work as I’ll have to move a ton of furniture and likely have whatever room being down unusable during that time. On the plus side, I could some of the ungrounded outlets grounded and ethernet run while in there.
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Mini-split upstairs - Between upstairs missing some insulation, not having a return vent, and well… being upstairs where heat rises to, the upstairs usually has a 10F or higher temperature difference. I’ve heard that doing this has halved some people’s electricity bills but I’m skeptical
Any tips are appreciated. Thank you!
You want to insulate first, otherwise anything else you do is just going to be pushing heat through your exterior walls. You should be able to get spray in insulation in those walls without needing to full tear down the drywall. Typically you’ll get a 1-2” hole on the top and bottom of each stud bay for foam to be sprayed in, then you patch that. It can be pricy up front but should pay off super quick if you have none right now (I’m still getting over 3,000 kWh… that just seems like an insane amount of electricity to use).
A mini split likely won’t help, you’ll just lose the cooling without insulation the same as without the mini split. You may want to look into balancing your ducting once you get the house insulated if you still have rooms that are too hot or cold. The bricks should help to stabilize temps and reduce swings over time but the effect is likely small and should be able to be ignored once you insulate.
Is there insulation on the exterior walls? If not then that seems like the biggest/best single thing to do. I would bet there’s some way they can shoot in some without destroying all the walls but idk.
I don’t see how a mini split, which is generally less efficient than a typical outdoor unit, helps at all.
Spray foam insulation is another thing to investigate for the attic.
Also, and this is outside the box, what about planting some trees to throw shade?
Just realized I put “interior” for the exterior walls in the post. There’s no insulation. My parents tried the “non-invasive” spray insulation by a company but it bowled out some of the walls and outlets after expanding and really didn’t look nice at all.
We have 2 trees in the front yard already. One medium and one large. The large one is dying and I will eventually replace. The 3 large trees across the street do help for early morning in the meantime.
You can actually do noninvasive with blown in insulation instead of foam and that won’t cause your walls to bow. TBH that’s what I would do first, and attic insulation if you haven’t got any.
Not a “real home improvement” guy, but my dad added radiant barriers to his attic some year back. I want to say he said he saw a ~15% reduction in AC usage back then which reduced the ~$300 bill (in peak summer) by about $50.
Radiant barriers always seemed like a low hanging fruit solution to help with summer cooling.
I’ll look into these. Thank you.
I’m a fan of insulating first because I find it more pleasant to have the house stay at the same temp longer rather than cycling between too hot and then too cold when the AC is running every couple of minutes.
We did a combination of R-38 batt insulation in the attic and blow in (i.e. drill & fill) for the exterior walls and it’s helped tremendously. Also, we added radiant heat barriers in the garage where there’s no HVAC. We had pros install all of this since it is fairly labor intensive to crawl around in the attic. They knocked it out in 2 days.
Another thing we did was get solar panels. Depending on your state’s current net metering policy, this could more than offset your entire usage. For us it made sense since we were also getting an EV in addition to having ever-increasingly hot summers.
If I had to replace the AC unit, I might look into a heat pump/mini-split like you mentioned since you don’t have to cool/heat the entire house if you don’t need to, but ours is still fairly new.
