Home electrification order of operations: why solar usually goes last

Solar, heat pump or EV: which first? If you are planning to electrify a Kentucky home, the order that usually holds up is: tighten the house, replace heating and water heating with heat pumps as the old equipment ages out, add the EV and its charging plan, settle the electrical capacity question with a licensed electrician, and size solar last, to the load you end up with.

The reason is simple. Solar is the only step on the list that has to be sized to a number, your annual kilowatt-hours, and every other step changes that number. Some steps push it up by thousands of kilowatt-hours. Others pull it down. Put solar first and you are sizing a 25-year asset to a house that is about to change.

Solar, heat pump or EV: which first, in one list

1. Air sealing and insulation. Cheapest kilowatt-hours to remove, and they shrink the heat pump you buy next.
2. Heat pump for space heating and cooling. Usually the biggest new electric load. Time it to the end of your furnace’s or air conditioner’s life.
3. Heat pump water heater. Often a load reduction if you have an electric tank today.
4. EV and a charging plan. A predictable load you can estimate from your mileage.
5. The panel question. Run it alongside steps 2 through 4, not after. It belongs to a licensed electrician.
6. Solar, sized to the new load. Now you have a number worth designing to.

This is a sequence, not a schedule. Few households do all six in one year. The point is to know where you are headed so each purchase fits the next one.

Why solar first can mis-size the array

Mis-sizing runs in both directions.

Too small. A home with a gas furnace that adds a heat pump and an EV can see annual electricity use jump by more than half. An array sized to the old bill then covers a shrinking share of the new one, and adding panels later can mean another interconnection application, roof space you no longer have, or an inverter that is already full.

Too big. A home with an electric-resistance water heater, baseboard heat or a furnace that leans on electric strips can see use fall after heat pumps arrive. An array sized to the old bill then exports more than the household uses. In Kentucky that matters, because export credits for new net-metering customers at the large utilities are set below the retail rate. Under LG&E and KU’s NMS-2 tariff, for example, each exported kilowatt-hour earns less than a kilowatt-hour you avoid buying. Our Kentucky net metering explainer walks through how that works.

Wrong season. Heat pump load peaks in December, January and February. A south-facing array in Lexington makes only about 18% of its annual output in those three months, and its December output is about half of August’s, based on PVWatts estimates. Solar can offset a heat pump’s kilowatt-hours over a year on paper, but the winter kilowatt-hours mostly come from the grid. That doesn’t make the pairing a bad idea. It means the savings depend on how your tariff credits summer exports against winter purchases.

A worked example: one Lexington house, four steps

Here is an illustrative house, not a real client. It’s a Lexington home with a gas furnace, central air and a 50-gallon electric-resistance water heater, using 11,000 kWh of electricity and 600 therms of gas for heating each year.

Assumptions, all illustrative:

• Furnace efficiency of 80%, so the house needs about 14,070 kWh of delivered heat a year.
• Air sealing and insulation cut that heating need by 20%.
• The heat pump averages a seasonal coefficient of performance (COP) of 2.4. HSPF2 is rated in Btu per watt-hour, so dividing by 3.412 gives a rough seasonal COP; 2.4 corresponds to an HSPF2 of about 8.2. ENERGY STAR’s minimum for split-system heat pumps is HSPF2 7.8.
• Hot water use of 50 gallons a day with a 67°F temperature rise. The electric tank has a uniform energy factor (UEF) of 0.93; ENERGY STAR cites that as typical for a standard electric storage heater. We model the heat pump water heater at an in-use 3.0, below the 3.3–4.1 range ENERGY STAR gives for certified models, to allow for a cool basement and occasional backup mode.
• 12,000 miles a year of driving at 0.32 kWh per mile, which leaves room for charging losses and winter driving. The most efficient 2026 EVs on FuelEconomy.gov are rated in the low-to-mid 20s of kWh per 100 miles; many crossovers are rated in the high 20s or around 30.
• Solar yield of 1,300 kWh per installed kW per year. PVWatts estimates about 1,355 for an unshaded, south-facing Lexington array at a 25° tilt with default losses; we trimmed it for a typical roof.

Step	Annual electricity (kWh)	Solar for 100% of annual use
Today	11,000	8.5 kW
Heat pump water heater replaces electric tank	8,783	6.8 kW
Envelope work, then heat pump replaces gas furnace	13,472	10.4 kW
EV added	17,312	13.3 kW

Three things stand out.

• The array sized to today’s bill covers about 64% of the final load. The gap is roughly 4.9 kW of panels.
• The water heater alone makes today’s array about 25% too big if nothing else changes. That’s the quiet surprise in the sequence. A heat pump water heater saves about 2,200 kWh a year in this example.
• Doing the envelope work first saves about 1,170 kWh a year of heat pump electricity. That’s roughly 0.9 kW of solar you never have to buy, and it can let the HVAC contractor specify smaller equipment.

The reverse case is just as instructive. If the same house heated with electric resistance instead of gas, it would use about 25,100 kWh a year today. After envelope work, a heat pump and a heat pump water heater, it would drop to about 13,500. An array sized to the old bill would produce roughly 86% more than the new load needs, and the surplus would earn the lower export credit.

Step by step: what each upgrade changes

1. Air sealing and insulation

Start with a home energy assessment by a qualified professional, ideally one who uses a blower door test to measure air leakage. Attic insulation, sealing the attic floor and duct sealing tend to come first because they are accessible and affect both heating and cooling. Ask the HVAC contractor to do a written heating and cooling load calculation after this work, not a rule of thumb based on square footage.

2. Heat pump

Compare models by HSPF2 for heating and SEER2 for cooling. ENERGY STAR’s split-system minimums are HSPF2 7.8 and SEER2 15.2. Its cold-climate tier also requires a COP of at least 1.75 at 5°F. You may not need a cold-climate model in central Kentucky, but cold snaps happen, and how much backup resistance heat a system uses on those days drives real-world kilowatt-hours. Ask how the backup heat is controlled.

3. Heat pump water heater

Heat pump water heaters move heat from the surrounding air into the tank, so placement matters. ENERGY STAR advises a space that stays between 40°F and 90°F with about 1,000 cubic feet of air around the unit. If you have a gas water heater, this step adds electric load instead of removing it. Some certified models run on a standard 120-volt, 15-amp circuit, which can matter for step 5. The best time to plan this is before the old tank fails, because emergency replacements tend to be like-for-like.

4. EV and charging

EV load is the easiest to estimate: annual miles times the vehicle’s rated consumption, plus a margin. LG&E and KU offer an Optimized EV Charging program that pays enrolled customers to shift some charging to lower-demand periods. If you are served by a co-op, Kentucky Power or Duke Energy Kentucky, ask what they offer.

5. The panel question, for a licensed electrician

We don’t evaluate electrical panels or service capacity. That’s a licensed electrician’s job, and the answer depends on a load calculation for your home. Bring these questions to that visit:

• With a heat pump, a heat pump water heater and an EV charger, does my existing service have capacity, or will it need an upgrade?
• Would a lower-amperage charger setting, a 120-volt water heater or a load management device avoid an upgrade?
• If an upgrade is needed, what does the utility’s side of the process involve, and how long does it take?
• Should I size the work for a future solar interconnection or battery now?

6. Solar, sized to the new load

By now you have 12 months of post-electrification bills, or a well-documented estimate. Size to that, and test the result at lower and higher loads. Ask each installer what adding panels later would involve. If you are weighing ownership options, our post on Kentucky solar after the federal tax credit covers the changed economics.

When solar first can still make sense

Sequencing is a default, not a rule. Solar first can be reasonable when the efficiency work is already done, the HVAC and water heater are new, the roof is due for replacement anyway, or you know your EV timeline well enough to size for it today. In each case the test is the same: can you write down the future load with confidence? If you can, size to it. If you can’t, wait or size conservatively.

What changed in 2026 for federal home credits

As of November 1, 2026. The 2025 budget reconciliation law, Public Law 119-21, ended several household credits early. According to the IRS:

• 25C (Energy Efficient Home Improvement Credit): not allowed for property placed in service after December 31, 2025. This covered heat pumps, heat pump water heaters, insulation and air sealing.
• 25D (Residential Clean Energy Credit): not allowed for expenditures made after December 31, 2025. The IRS treats an expenditure as made when installation is complete, so a system paid for in 2025 but finished in 2026 doesn’t qualify.
• 30D and 25E (new and used clean vehicle credits): not allowed for vehicles acquired after September 30, 2025.
• 30C (refueling property credit, which included home chargers in eligible census tracts): not allowed for property placed in service after June 30, 2026.

The practical effect is that there’s no longer a federal deadline pushing you to rush any step. Order the work by equipment age and by load. This is general information, not tax advice; confirm anything that affects your return with a tax professional.

State and utility programs. Kentucky’s Home Energy Rebates program, funded by the Inflation Reduction Act and administered by the Energy and Environment Cabinet’s Office of Energy Policy, says on its website that it is not yet accepting rebate applications, and it warns that anyone offering these rebates is misinformed. Treat a contractor’s quote that subtracts a state rebate with caution. LG&E and KU list residential rebates for qualified ENERGY STAR heat pumps and heat pump water heaters, an online home assessment and kit, and a WeCare program for income-qualified customers. Programs, amounts and eligibility change, so check your utility or co-op before you buy.

What we’d do

• Pull 12 months of electric and gas bills and write down the age of your furnace, air conditioner and water heater.
• Sketch a five-year plan: which equipment ages out when, and when an EV is likely.
• Get the envelope work done, then the load calculation, then the heat pump.
• Book the electrician conversation before the big equipment is ordered.
• Model solar against the post-electrification load, with a range, and compare it to what proposals assume.

That last step is what our Solar Readiness Consultation is for. We don’t sell panels, heat pumps or chargers, and we don’t install anything. In a 75-minute session, with a written summary within three business days, we build the load picture from your documents, give you a preliminary range of array sizes worth evaluating, and list the questions to bring to your electrician and installers. If you are earlier in the process, our page for Kentucky homeowners is a good place to start.