Here are ideas for energy-efficient home improvement at the $500, $1,000, $5,000 and $25,000 levels:
Caulking/sealing air leaks
Before installing every fancy gadget and energy-efficient appliance, sealing air leaks from windows, doors and walls is always the first step toward a more energy-efficient home. If you can't afford an energy audit and weatherstripping, then you probably qualify for the federal government's weatherization program, which will subsidize these projects. (See AOL Real Estate's guide: Home Improvement Grants Give Homeowners a Boost.)
This isn't exactly breaking news anymore, but if you haven't already switched to compact fluorescent bulbs, this is step two. If you can't abide the harsh light of fluorescents, new incandescent bulbs are 30 percent more energy-efficient.
Outdoor solar lighting
This might seem redundant, but it's worth emphasizing the point that, on a shoestring budget, it's best to focus home improvements on eliminating drafts and needless expenditures. And there's simply no reason to use electricity for outdoor lighting anymore. These lights will channel the sun's daytime energy into free nighttime illumination.
Replace exterior doors
A more permanent and superior solution to weatherstripping is installing new exterior doors. Energy loss through these doors is about half that of windows. Installation is a large part of this cost, so replacing multiple doors in one shot should lead to a good chunk of savings. (Find highly rated window and door professionals in your area.)
Install a programmable thermostat
As it is with many things, timing matters when it comes to energy use. Despite the extra energy needed to compensate later in the day, shutting off systems in the daytime and trimming use in the middle of the night can still save a substantial amount of energy and cost. (Find highly rated air conditioning professionals in your area.)
It doesn't get a lot of attention, but window coverings aren't just about interior decorating. Versatile window coverings can allow you to employ effective daylighting strategies that will take the burden off interior lighting. In some cases, you may want a covering that will act as a makeshift insulating shield for your window glass. (Find highly rated decorators and designers in your area.)
Upgrade water heating
Ideally, you'll install a solar water heating system that will achieve unmatched energy-efficiency and a longer lifespan, but even tankless water heating systems and better-insulated hot water tanks can be a significant upgrade over older units. (Find highly rated professional plumbers in your area.)
Replace a major appliance(s)
Refrigerators are best, followed by washers and dryers, but you should also evaluate those appliances which are oldest and closest to failure. Even replacing dishwashers, oven ranges and microwaves can make a sizable difference.
Whether it's blown into wall cavities or rolled onto attic space, there is usually a worthwhile opportunity for new insulation. Though it sounds straightforward, you'll need to consult with a contractor who can knowledgeably identify the area of greatest need and the most cost-effective solution. (Learn more about this with AOL Real Estate's guide: Insulation at Home Saves Money.)
This energy-efficient home improvement has become the poster child for green home improvements over the years. It's costly, but it delivers matching -- even surpassing -- cost-savings. Rarely a bad idea, if you still have single-pane windows on your home, this project is priority one for larger budgets. (Find highly rated window and door professionals in your area.)
Upgrade heating and/or cooling system
If either system is advancing in years, it's time to start researching the possibilities. Heat pumps, zoning schemes, hydronic heating, swamp coolers, geothermal, and new Energy Star furnaces and air conditioners are all options, the best of which can be assessed by a local HVAC contractor. (Find highly rated air conditioning professionals in your area.)
Roofing or siding
Major financial investments should continue to pay off decades later. Energy-efficient roofing or siding will reduce your heating and cooling bills, while enhancing your home's curb appeal and ensuring its structural integrity. Talk to contractors about which materials fit best with your local climate. (Find highly rated roofing professionals in your area or siding professionals.)
Listing these budget strategies with three steps is not an arbitrary decision. Just like your general home improvement and remodeling budget, spreading your financial resources throughout your home usually creates the best energy-efficiency returns.