Twenty-Two Thousand Dollars in Tucson

Two gates must be cleared first, and neither is a credit decision

1. Minimum energy performance The energy prerequisite sets a performance floor. A HERS 62 may or may not clear it depending on the current threshold and the reference home used. Before spending a dollar on upgrades, have the rater produce the prerequisite compliance calculation, not just the index number. Two things commonly distort the preliminary figure: the wrong conditioned floor area or volume, and a reference home that does not match the as-designed glazing and duct location. If the model inputs are wrong, the project may already comply and the $22,000 conversation changes completely.

2. Indoor water use The water prerequisite compares design fixtures against a baseline. 2.5 gpm showerheads and 1.6 gpf toilets are close to the baseline plumbing, so verify the calculation rather than assuming either pass or fail. If the fixture package is what closes the prerequisite, the $1,400 quote is not optional - it is the price of eligibility, and it should be booked before any discretionary spending.

Also settle the envelope question Twelve percent duct leakage to outside in a 2B attic is not just an energy number. It is a pressure and comfort problem, and in a hot-dry climate it also pulls dust and attic air into the supply. Fixing it may be needed for other prerequisites and credits even if the HERS gain were zero.

Why the order matters Prerequisites do not score. A dollar spent clearing one looks like zero points per dollar, so an optimization spreadsheet will always rank it last - and that is exactly the trap. Clear the gates, then optimize the remaining budget for points. Do not let the model's point column drive sequencing.

Ranked by value, with the reasoning made explicit

Buy now: fixtures, $1,400. Cheapest item on the list, closes or secures the water prerequisite, and typically moves the indoor water-use credit as well. Even at one point this is the best dollars-per-point in the package. No schedule risk.

Buy now: duct sealing and interior ducts, $6,500. Six HERS points is the largest modeled efficiency gain available, and it is permanent, verifiable, and improves comfort - which matters for a builder's warranty calls. Moving ducts inside the envelope also reduces the risk of a future rater dispute over duct leakage assumptions. Points per dollar is strong, and the measure is durable.

Buy now: turf removal, $8,000. In Climate Zone 2B, 1,500 sq ft of irrigated Bermuda is the single largest water load on the property. Removing it and installing native xeriscape with drip usually earns the outdoor water credit outright, and it also reduces the irrigation demand that the landscape must meet. Confirm whether the credit requires eliminating permanent irrigation entirely or a percentage reduction - that detail determines whether drip stays. Slower to earn than fixtures but far cheaper per point than windows.

Defer: windows, $14,000 for 3 HERS points. Worst value on the list by a wide margin, and it consumes 64% of the budget. The same money buys fixtures, duct work, and the landscape.

Right-size, don't delete: PV. With $6,100 remaining after the three items above, a 2 kW array is a reasonable buy after the ducts are sealed. Do not size PV against the current HERS 62 - seal the ducts first, re-run the model, and let the final array match the gap to the next credit tier. Also confirm ownership and documentation, since a leased system is harder to verify.

Water heater, $3,800, is the swing item. If it fits after PV, it lowers the HERS index and removes an atmospheric appliance from the garage. If not, it is the first thing to add when the budget grows.

Valid on the scorecard, weaker on everything else

Where the argument holds The Energy and Atmosphere credit is scored from the HERS index, and on-site PV lowers that index. If 5 kW of PV moves the project into the same or a better credit tier than duct sealing would, the points are equivalent in the arithmetic. However, check the credit language for how renewable generation is treated and whether there is a cap or a separate efficiency expectation - do not assume the modeled HERS reduction converts one-for-one into credit tiers before the rater confirms it.

Where it fails

• Permanence. Duct sealing inside the envelope is part of the house for its life. Panels degrade, inverters fail, and a later owner may remove them. The rating system is measuring the house, not the owner's willingness to maintain equipment.
• Prerequisites and verification. If the PV is not installed and documented at final verification, the projected HERS index evaporates and the energy prerequisite may fail with it. That risk sits on the critical path to closing.
• Comfort and durability. Leaky attic ducts in Tucson mean hot supply air, uneven room temperatures, and higher static pressure. PV pays the bill; it does not fix the house. A house with a PV-driven HERS index and 12% duct leakage is a comfort complaint waiting to happen.
• Credit interactions. Duct location and leakage often support other credits, and interior ducts reduce the risk of condensation issues. PV supports none of that.

The defensible sequence Spend on efficiency first - ducts, then fixtures, then landscape - and treat PV as the last increment sized to close the remaining gap. That order is also the honest one to give a buyer: the house performs better before the panels are added, not only after.