So, alright. I’ve got a 1926 square foot house I’d like to lower the electric bills on. (and, have fun installing new equipment)
Location : Houston, Texas.
I could pay for foam insulation injected into the walls. Apparently, that would cost about 4-8k.
I could buy more efficient air conditioners. Currently, the A/C has a SEER rating of 15. It cools the entire house. Replacing it would cost about $5000 (4k for the unit, 1k for replacing the worn out ductwork)
I could purchase ductless split A/Cs for the entire house. If I paid for the equipment and did the installation myself, it would cost about $1750 each for Fujitsu 9RLS3s. I would need about 5 of them. They have a SEER rating of 33. The SEER scale is linear, right? So I’d save at least half the power consumption. Since the A/Cs only cool the rooms actually in use, I think I’d save about half again as a lot of the house is empty almost all of the time. The climate is warm, so I’d turn off gas service and use the heatpump mode for the winter time.
I could build a solar array. Tax credit expires at end of 2016, so I’m thinking I’d buy the array in February 2016, since I suspect prices on solar equipment will stay flat or even increase during the rush before the tax credit expires, so I might as well have the array installed before summer. I’d do all the work myself on that except for the hookups at the box.
The smart money is always on efficiency improvements (“Negawatts”).
A SEER 15 A/C is pretty efficient - even at 50% energy savings with a SEER 33 unit, your payback period for $8,750 worth of new A/Cs is going to be a really long time.
I’d do an energy audit and see where your leaks are…
Like beowulff said, an energy audit is the way to go. We brought in a company to test our house for leaks (they use thermal cameras and air pumps to pump air into the walls and such and tell you where you need more insulation or new windows or whatever…we needed a lot) and I think it’s saved us a ton even though it was a bit expensive. I also have solar and to be honest I haven’t gotten my money back out of the system and I’m probably going to be replacing panels in the next few years before we even broke even (also, I’ve nearly killed myself a couple times up there cleaning them and such…next time I’m getting a service contract!).
Your local electric utility or various other organizations might even do an energy audit for you for free. If you can get it for free, it’s definitely worth the price.
How much do you currently pay for air conditioning, and how much for heating? How many degree-days do you have of each per year?
I’d only install 4 of the ACs when the old central system fails and needs replacing anyways. So it’s actually a payback period for $3750 of more efficient A/Cs. If my current bills are $1800 a year, and I cut them to $900, then that’s a 4 year payback.
Of course, making this more complex is that I’d be doing all the work myself with the more efficient A/C install, while I could just hire a professional to do the main A/C install for 5k. (the reason I would have to do it all myself is that professionals charge exorbitant prices for installing ductless A/Cs even though all you have to do is connect 4 fittings, torque em down, and vacuum pump the lines clear)
See if you get discounts for “green” technologies. I went with a ground source heat exchange system several years ago, and all of my electricity on its separate meter is priced at 50% of normal residential pricing.
Either I am way over-estimating the effect of a dark roof in bright (and hot) sun, or a lot of people are wasting money by not considering the effect.
Next up - how well is the attic:
Insulated?
Ventilated?
DO NOT USE “whole house” exhaust fans - this is an example of “Good idea taken so far it becomes a bad one” - yes, you want that hot air gone. No, you do not want the air you just cooled being sucked up to replace the hot air.
And another vote for audit, assuming you have done the basics of double paned windows, awnings or shade of some sort on the south-facing side, attic insulation blown in.
Hint: have the attic insulation blown in during the off-season. It is hot up there and the hotter, the less time anybody is going to spend making sure everything is just right.
When we lived in Davis, CA whole house fans were common and a fantastic thing to have. At night, when the valley cooled to the 60s, you could just open the windows, turn on the fan and the whole house would cool down in less than 10 mins (then you could shut the fan off) and stay cool all night.
Not sure Texas gets cool enough at night for it to be worthwhile.
What kind of thermostat do you have? Depending on the type, you may get mileage out of getting one of the newer ones on the market, like a NEST or if your thermostat is particularly antiquated, a programmable one.
An attic exhaust fan (NOT a whole-house exhaust fan) might be worthwhile if you have vented soffits.
Don’t forget to consider you might be eligible for energy tax credits when you do cost calculations. It is possible you could insulate your house and have a more energy efficient system installed as well because tax credits from one may offset the cost of the other.
From a couple of minutes of googling. Foam Insulation claims to cut power bills by 22%. An SEER 15 would cut power bills by 35%, the SEER 33 claims a 50% reduction and the solar arrays claim a 50% deduction. So the SEER 33 or the solar gives you the best return if your power bills are 1800 a year. Solar might be cost competitive if you get a bunch of subsidies. There is also the risk of going with a less mature technology.