What summer energy bills really look like in St. George

Typical ranges by home size

Rocky Mountain Power is the primary utility serving Washington County. Monthly summer bills vary widely based on home size, construction era, and thermostat habits, but these ranges hold for most conventional homes:

• 📈
  Under 1,500 sq ft$150 to $250 per month in July and August. Efficient construction and sensible thermostat settings keep it toward the lower end.
• 📈
  1,500 to 2,500 sq ft$220 to $380 per month during peak cooling months. The middle of most single-family homes in the St. George market.
• 📈
  2,500 to 4,000 sq ft$320 to $550 per month or higher for older builds with poor insulation, west-facing walls, or undersized HVAC systems running extended cycles.

These figures assume central air conditioning as the primary cooling system. Pool pumps, irrigated landscaping, and older appliances can add $50 to $150 on top of these ranges.

What actually drives the bill up

• 🌞
  West-facing glazingWindows and glass doors facing west accumulate direct afternoon sun from June through September. Homes with large west-facing windows that lack exterior shading run significantly warmer through the evening cool-down window.
• 🕑
  HVAC age and sizingA unit that is more than 12 to 15 years old or that was undersized for the home's actual square footage runs longer cycles to maintain temperature, burning more electricity per degree of cooling.
• 🏠
  Attic insulationRadiant heat through the roof is the dominant gain mechanism in this climate. Homes with older or settled attic insulation — common in 1990s and early 2000s builds — transfer significantly more heat into the living space than newer construction with modern insulation values.
• 💧
  Landscaping and shadeMature desert landscaping with shade trees on the south and west faces can reduce cooling load meaningfully. A bare lot with no shade structure has no buffer against direct solar gain.

Red flags when you are buying

• 🚩
  Seller cannot produce utility historyIn a hot-climate market, asking for 12 months of electricity bills is standard due diligence. A seller who cannot or will not provide it is leaving you to guess at one of the largest recurring costs of the home.
• 🚩
  HVAC installed more than 12 years agoYou may be buying a near-term replacement. A qualified inspector can assess efficiency, but budget $5,000 to $12,000 for a residential system replacement if it fails within your first few summers.
• 🚩
  No shade on west and south faces in a newer buildBuilder-installed desert landscaping often starts small. Verify whether the builder provided any sun mitigation on the high-exposure elevations, or factor in the cost and time to establish your own.
• 🚩
  Summer bills not matching the home sizeIf the utility history shows bills that seem low for the home, ask why. It could indicate a thermostat set unusually high, the home sitting vacant for part of the season, or a discrepancy in usage that will not hold once your family is living there full-time.

How to manage costs once you move in

• 🏠
  Pre-cool before peak hoursRocky Mountain Power's time-of-use rates charge more between 3 pm and 9 pm in summer. Running the system harder in the morning and letting the house coast through the expensive window cuts costs without reducing comfort much.
• 🏠
  Attic insulation auditIf the home is from the 1990s or 2000s, an insulation inspection is worth doing early. Bringing attic R-value up to current standards is one of the highest-return upgrades in this climate.
• 🏠
  Exterior window screens or solar shadesExterior solar screens on west-facing windows block 80 to 90 percent of heat gain before it enters the glass. Interior blinds block light but not heat. The location of the screen matters.
• 🏠
  Schedule HVAC maintenance before summerApril or May service — cleaning coils, checking refrigerant, verifying thermostat calibration — gives you the full season of efficient operation rather than discovering a problem during a heat event in July.

Related guides