Heating and cooling — HVAC in the industry shorthand — is the single largest energy expense in most homes. The US Energy Information Administration estimates it accounts for roughly 45-50% of a typical home’s total energy use.
That’s not electric lighting, not appliances, not the water heater — just keeping the house at a comfortable temperature. On an average American utility bill of $115/month, that’s $52-58/month for temperature control alone.
The good news: heating and cooling is also the energy category with the most available savings — because so much of the cost is determined by how you manage and maintain the system rather than by the system itself. A well-managed HVAC system in a properly sealed home costs significantly less to run than a neglected system in a leaky one, even when the equipment is identical.
This guide covers the complete year-round approach — the one-time fixes, the seasonal habits, the equipment decisions, and the behavioral changes that together produce the most significant and durable energy savings available in any home.
Understanding What You’re Paying For
Before strategies, the physics — because understanding how heat works makes the interventions intuitive rather than arbitrary.
Heat moves from warm to cold. Always. In winter, the heat inside your home is constantly moving toward the colder outside. Your heating system’s job is to replace that heat as fast as it leaves. In summer, the heat outside is constantly moving toward your cooler interior. Your cooling system’s job is to remove it as fast as it arrives.
The rate of heat transfer is what costs money. A well-insulated, well-sealed home loses heat (or gains it) slowly — requiring less system output to maintain temperature. A poorly insulated, leaky home loses or gains heat rapidly — requiring constant system output.
Everything in this guide either slows the rate of heat transfer or makes the system more efficient at managing it. Both reduce the energy required and therefore the bill.
The Thermostat: The Highest-Leverage Tool You Already Own
The thermostat is the most direct control you have over heating and cooling costs — and most people use it far less strategically than they could.
The Setback Strategy
For every degree you lower your thermostat in winter (or raise it in summer), you save approximately 1-3% on your heating or cooling bill. This is not a linear relationship — the savings compound as the temperature differential between inside and outside decreases.
Winter setback targets:
- When awake and home: 68°F (20°C)
- When asleep: 65°F (18°C) — the body’s sleep temperature requirements are lower, and extra blankets cost nothing
- When away from home: 62°F (17°C) — low enough to save significantly, high enough that pipes won’t freeze and the home won’t take excessive energy to reheat
Summer setback targets:
- When awake and home: 78°F (26°C) — warmer than people often prefer, but fans make this feel significantly cooler (more below)
- When asleep: 80-82°F (27-28°C) — ceiling fan running, window open if outside temperature drops
- When away from home: 85°F (29°C) — no reason to cool an empty house
The math on winter setback: A home that’s kept at 72°F 24/7 versus one kept at 68°F during the day, 65°F at night, and 62°F when empty saves approximately 10-15% on winter heating — $15-25/month on an average heating bill — from thermostat management alone.
Programmable and Smart Thermostats
A programmable thermostat automates the setback strategy — it runs the schedule you program without requiring you to remember to adjust every time you leave or go to sleep.
The DOE estimates a properly programmed setback thermostat saves 10% on annual heating and cooling costs.
Programmable thermostats: $25-50 at any hardware store. DIY installation in 30-45 minutes for most systems. Pays for itself in the first month on typical heating bills.
Smart thermostats (Nest, Ecobee, Honeywell Home): $100-250. Learn your patterns automatically, allow remote control from your phone, provide usage analytics. The savings are similar to a programmable thermostat for most households — the premium buys convenience and data rather than dramatically better savings.
The installation reality: Most thermostats are straightforward DIY projects — take a photo of the wiring, follow the instructions, swap the devices. As covered in our DIY home repairs guide, the initial intimidation is usually much greater than the actual difficulty.
THRIFTY HABIT #213 Program your setback thermostat this week. The actual setup takes 20-30 minutes once the thermostat is installed. If you already have a programmable thermostat that’s been set to one temperature because nobody took the time to program it, program it today. The savings start immediately and run indefinitely.
Air Sealing: The Most Cost-Effective Improvement Available
The DOE estimates that air infiltration — air leaking through gaps and cracks in the building envelope — accounts for 25-40% of a home’s heating and cooling costs. In an older or poorly maintained home, this number can be higher.
As covered in our DIY home energy audit guide, finding and sealing these leaks is the single highest-return improvement available in most homes — because the materials cost $20-50 and the labor is simple.
The most significant air leak locations:
Around windows and doors: Caulk where the frame meets the wall. Weatherstripping on door frames and window sashes. Door sweeps on exterior doors. These are the first and most impactful places to check.
Electrical outlets and switches on exterior walls: A foam gasket behind the cover plate ($3-5 for a pack) seals what is often a direct path to the wall cavity and outside air.
Where pipes and wires enter through exterior walls: Expanding foam sealant in the gap around any penetration through an exterior wall. Takes 2 minutes per location, costs $0.50-1.00 in materials, and eliminates what can be a significant air path.
Attic hatch: One of the most overlooked and most significant air leak locations. Weatherstripping around the hatch frame and rigid insulation attached to the hatch panel seal what is often a direct connection between living space and the unheated attic.
Fireplace dampers: When not in use, an open fireplace flue is essentially a hole in the roof. A chimney balloon or damper plug ($25-50) seals it during non-use seasons. A poorly sealed damper can account for 5-10% of a home’s air leakage by itself.
Total investment for a thorough air sealing job: $50-150 in materials, one Saturday of work. Typical annual savings: $200-400 on energy bills. Payback period: 3-6 months.
Insulation: The Long-Term Investment
If air sealing is the most cost-effective improvement, insulation is the most durable one. Once installed, insulation requires no ongoing maintenance and continues performing indefinitely.
Attic insulation: The attic is where most homes lose the most heat — because heat rises and escapes through the ceiling into the cold attic space. Current DOE recommendations call for R-38 to R-60 in attics depending on climate zone (roughly 12-20 inches of blown-in insulation).
If you can see floor joists clearly through your attic insulation, you’re significantly under-insulated. Adding blown-in insulation is among the most impactful single home improvements available:
- DIY with rental equipment: $500-800 for a typical house
- Professionally installed: $1,500-3,000
- Annual energy savings: $200-600
- Payback period: 2-5 years
Wall insulation: Harder to add in existing homes, but where walls have been opened for renovation, insulating is always worthwhile.
Basement and crawl space: Insulating the rim joist (where the foundation meets the framing) with rigid foam or spray foam is a highly accessible improvement that reduces heat loss through what is often a poorly sealed and poorly insulated area.
HVAC System Maintenance: Getting More From What You Have
The efficiency of your heating and cooling system degrades when it’s poorly maintained. Regular maintenance keeps it running at or near its designed efficiency — avoiding the energy waste of a struggling system.
Filter Changes
As covered in our DIY home energy audit guide, a clogged air filter restricts airflow through the system, making the blower work harder and longer to move the same amount of air. This wastes energy and shortens equipment life.
Change the filter every 1-3 months depending on your household (more often with pets or in dusty environments). A $5-10 filter replaced on schedule saves significantly more in energy costs than it costs.
Set a phone reminder if you tend to forget — this is the easiest maintenance item on this list and one of the highest-return.
Annual Professional Service
A qualified HVAC technician checking refrigerant levels, cleaning coils, checking electrical connections, and calibrating the system annually:
- Catches problems before they become expensive failures
- Maintains efficiency (a dirty evaporator coil can reduce efficiency by 5-10%)
- Extends equipment life
Cost: $80-150/year. Return: energy savings from maintained efficiency plus avoided repair costs that dwarf the service fee.
Duct Inspection and Sealing
Duct leaks — air escaping from the supply or return duct system before reaching the rooms it’s intended to condition — are one of the most consistently underestimated efficiency losses in homes with forced air systems.
The DOE estimates that duct leaks account for 20-30% of the conditioned air in a typical forced air system. Air you paid to heat or cool, escaping into the attic or crawl space.
Accessible duct sections (in basements, attics, and crawl spaces) can be sealed with mastic sealant (not regular duct tape, which fails within a few years). A professional duct testing and sealing service costs $300-500 and typically produces 15-25% improvement in system efficiency.
Seasonal Strategies: Winter Specifics
Let the Sun In
South-facing windows receive solar gain during winter — the sun’s energy converting to heat as it enters through glass. Opening blinds and curtains on south-facing windows during daylight hours provides free supplemental heating. Closing them at night prevents that heat from radiating back out through the glass.
This passive solar strategy costs nothing and provides meaningful free heat on sunny winter days.
Reverse Ceiling Fan Direction
Ceiling fans have a reverse setting — the blade rotation direction can be switched from counterclockwise (summer) to clockwise (winter). In clockwise rotation at low speed, the fan pushes warm air that has accumulated near the ceiling down the walls and back into the living space rather than pulling cool air up.
The switch is a button on the fan’s motor housing. Takes 5 seconds. Can reduce heating costs by up to 10% in rooms with high ceilings where warm air stratification is significant.
Space Heaters for Zone Heating
If you spend most of your time in one or two rooms, heating the entire house to 68°F while you’re in one room is inefficient.
Zone heating — keeping the whole house at 62°F and adding a space heater in the room you’re occupying — can be more efficient than whole-house heating when the occupied space is a small fraction of the total square footage.
The math: An 1,500-watt electric space heater running 8 hours/day costs approximately $1-1.50/day to operate. If it replaces 5 degrees of whole-house gas heating in a 2,000 sq ft home for those hours, the comparison depends on your local gas and electric rates — but for many households, zone heating is genuinely cheaper.
The safety caveat: Never leave space heaters unattended or use them near flammable materials. Follow all manufacturer safety guidelines.
Seasonal Strategies: Summer Specifics
The Fan-Thermostat Combination
Ceiling fans and box fans don’t cool air — they cool people through the wind chill effect. A person in a room at 78°F with a fan running feels as comfortable as a person at 72°F without one.
This means every degree you can raise the air conditioning setpoint while maintaining comfort with fans produces energy savings. The typical adjustment: a ceiling fan allows raising the AC setpoint 4°F with no perceived comfort change.
Energy comparison: Running a ceiling fan costs $0.01-0.02/hour. Running a 3-ton central air conditioner costs $0.25-0.40/hour. For every hour a fan replaces air conditioning, you save $0.23-0.38.
The fan must be turned off when the room is unoccupied — fans cool people, not rooms. A fan running in an empty room is pure waste.
Block the Heat Before It Enters
Preventing solar heat gain in summer produces more cooling savings than removing that heat after it enters.
Window film: Reflective or low-e window film applied to south and west-facing windows blocks 50-80% of solar heat gain. Cost: $30-60 for a typical window, DIY installation. Particularly effective in climates with strong summer sun.
Exterior shading: Awnings, exterior shutters, and deciduous trees on the south and west sides block sun before it reaches the glass — more effective than interior window treatments because the heat is blocked before entering the glass.
Blackout curtains: Interior blackout curtains block heat gain significantly more than standard curtains. Cost: $20-50 per window. Keep them closed on south and west-facing windows during peak sun hours (typically 10am-4pm).
Ventilation Timing
In climates where nighttime temperatures drop significantly below daytime temperatures, night ventilation is a powerful free cooling strategy.
Open windows once outdoor temperature drops below indoor temperature — typically after 9-10pm. Run fans to bring cool air in. Close windows and curtains in the morning before outdoor temperature rises above indoor temperature. The mass of the house retains the cool from overnight for several hours into the morning, delaying when the air conditioner needs to run.
This strategy is most effective in climates with significant day-night temperature differential (15°F+ difference) and less effective in humid climates where nighttime temperatures stay high.
Don’t Add Internal Heat Loads
Your cooling system has to remove both outdoor heat infiltration and heat generated inside the house. Reducing internal heat sources reduces the cooling load during summer:
- Cook outdoors on the grill or use the microwave rather than the oven on hot days
- Run the dishwasher and dryer in the evening when outdoor temperatures are lower
- Switch remaining incandescent bulbs to LEDs (incandescents produce 90% of their energy as heat rather than light — in summer this is an air conditioning load)
- Turn off electronics and lights when not in use
Equipment Decisions: When to Upgrade
The HVAC system itself — not just how it’s managed — determines efficiency ceiling. An older, lower-efficiency system has real operating cost disadvantages over a modern efficient one.
The upgrade decision framework:
Don’t upgrade a functioning system purely for efficiency if the payback period exceeds the likely equipment life remaining. A 10-year-old system with 10-15 years of remaining life may not be worth replacing for efficiency alone.
Do upgrade when:
- The system needs major repair (at or near the cost of replacement)
- The system is near the end of its useful life (15-20+ years for most equipment)
- You’re doing a major renovation that involves opening walls and ceilings anyway
What to look for when replacing:
- SEER rating for air conditioners (minimum 16 SEER for meaningful efficiency, 20+ for best-in-class)
- AFUE rating for gas furnaces (95%+ for high-efficiency)
- Heat pumps instead of separate heating and cooling systems — modern heat pumps handle both and are significantly more efficient than resistance heat
The heat pump opportunity: Electric heat pumps have become significantly more efficient in cold climates in recent years, and with electricity prices and gas prices varying by region, may represent the most cost-effective heating and cooling solution for homes replacing aging systems — particularly with available federal and state incentives.
The Annual Savings From a Systematic Approach
| Strategy | Annual Saving | One-Time Cost |
|---|---|---|
| Thermostat programming | $150 – $300 | $0 (existing) – $50 (new programmable) |
| Air sealing | $200 – $400 | $50 – $150 |
| Filter replacement habit | $30 – $80 | $5-10/month ongoing |
| Ceiling fan direction (winter) | $50 – $100 | $0 |
| Ceiling fan instead of AC (summer) | $80 – $150 | $0 (existing fans) |
| Blocking solar gain (summer) | $80 – $150 | $50 – $200 |
| Annual HVAC maintenance | $100 – $200 (avoided costs) | $80 – $150/year |
| Attic insulation (if under-insulated) | $200 – $600 | $500 – $3,000 |
| Total (lower-cost strategies) | $590 – $1,180/year | $100 – $400 one-time |
The no-cost and low-cost strategies — thermostat management, fan optimization, solar blocking, filter changes — produce $400-800 in annual savings. The modest-cost improvements — air sealing, programmable thermostat — add another $250-450 in annual savings at a one-time cost of $50-200.
The payback period on every strategy in this guide except attic insulation is under six months. Most are immediate.
Combined with the specific strategies from our save money on your electric bill and DIY home energy audit guides, a systematic approach to heating and cooling costs produces the largest single-category reduction in home energy spending available to most households.
What’s the heating or cooling change that made the biggest difference in your home — and what was the cost to implement it? Drop it in the comments!
