How to Do a Home Energy Load Audit (Step by Step)
How to Do a Home Energy Load Audit (Step by Step)
Every off-grid sizing mistake starts the same way: someone buys the equipment first and does the math later. The panels arrive, the batteries arrive, the inverter arrives — and then the well pump kicks on and the whole system falls over.
A home energy load audit prevents that. It's simply a careful accounting of everything in your house that uses electricity, how much each thing draws, and how long it runs. Thirty minutes with this process saves you from buying twice as much equipment as you need — or half as much.
This is step one of our complete series on taking a 2,000 sq ft house fully off-grid. Do this first. Everything downstream — solar panels, batteries, inverters — gets sized from the number you calculate here.
What a Load Audit Actually Is
A load audit answers one question: how many kilowatt-hours (kWh) does your house use per day?
That single number drives every decision that follows:
- Solar array size = daily kWh ÷ your area's sun hours (plus losses)
- Battery bank size = daily kWh × days of backup you want
- Inverter size = the biggest simultaneous draw in your house
Get the number right and the rest is arithmetic. Get it wrong and nothing downstream works.
Step 1: List Every Electrical Load in Your House
Walk through your house room by room and write down everything that plugs in or is hardwired. Don't skip the boring stuff — the water heater and the well pump matter far more than the phone chargers.
Here are realistic wattages for the big items in a typical 2,000 sq ft home. Your exact models will differ, so check the nameplate on each appliance (it's the sticker or plate showing volts, amps, and watts).
| Appliance | Typical running watts | Notes |
|---|---|---|
| Central AC (3-ton) | 3,500 | The single biggest load in most homes |
| Electric water heater | 4,500 | Runs 2–4 hrs/day typically |
| Electric dryer | 3,000–5,000 | Short cycles, huge draw |
| Electric range/oven | 2,000–5,000 | Burners cycle on/off |
| Well pump (1 HP) | 750–1,000 running | 3–5× surge at startup |
| Refrigerator | 150–200 running | Cycles ~8 hrs/day |
| Deep freezer | 100–150 running | Cycles ~8 hrs/day |
| Dishwasher | 1,200–1,500 | Mostly the heating element |
| Washing machine | 500 | Motor only; dryer is the hog |
| Microwave | 1,000–1,200 | Short bursts |
| Space heater | 1,500 | Per heater — these add up fast |
| LED lighting (whole house) | 100–200 | Old bulbs? Triple this |
| TV + entertainment | 150–300 | — |
| Computers + office | 200–400 | — |
| Internet/modem/router | 20–50 | Runs 24/7 — don't forget it |
The pattern to notice: heating and cooling dominate everything. An electric water heater and a central AC together can exceed every other load in the house combined. This is why the first question in any off-grid plan is always about heat — more on that in the FAQ.
Step 2: Estimate Daily Run Hours for Each Load
Watts tell you the rate of use. To get energy, multiply by time:
Watts × hours per day ÷ 1,000 = kWh per day
Be honest about run hours. The fridge doesn't run 24 hours — its compressor cycles roughly a third of the time. Your AC might run 8 hours on a mild day and 16 in August. Use your heaviest realistic day for sizing; you can note a mild-day number separately.
Worked mini-example:
- Refrigerator: 175W × 8 hrs ÷ 1,000 = 1.4 kWh/day
- LED lights: 150W × 5 hrs ÷ 1,000 = 0.75 kWh/day
- Well pump: 900W × 1.5 hrs ÷ 1,000 = 1.35 kWh/day
- TV + office: 300W × 6 hrs ÷ 1,000 = 1.8 kWh/day
- Router/modem: 30W × 24 hrs ÷ 1,000 = 0.72 kWh/day
Running total so far: 6.02 kWh/day — and we haven't touched heating, cooling, hot water, or laundry yet.
Step 3: Account for Surge (Starting) Watts
Motors draw far more power at startup than while running. This is called surge or locked-rotor current, and ignoring it is the #1 cause of undersized inverters.
Typical surge multipliers:
- Well pump: 3–5× running watts (a 900W pump can surge to 4,500W)
- Refrigerator compressor: 3–4×
- Central AC: 3–5× (a 3,500W unit can spike past 15,000W)
- Power tools, table saws: 2–3×
Write the surge number next to each motor load. Your inverter must handle the largest single surge in the house plus whatever else is running at that moment. This is exactly what our inverter sizing guide walks through in Part 5 of this series.
Step 4: Add the Loads Everyone Forgets
These are small individually but they run constantly, and they add up:
- Phantom loads — TVs, game consoles, chargers, and smart devices draw 5–50W each even when "off." A house with lots of standby electronics can waste 1–2 kWh/day doing nothing.
- Garage door opener, doorbell transformer — small, always on.
- Septic pump, sump pump — intermittent but real.
- Security cameras, smart home hubs — 24/7 draws.
A Kill-A-Watt meter ($25–35) plugged into each outlet for 24 hours gives you exact numbers instead of guesses. For a load audit that drives thousands of dollars in equipment decisions, it's the best $30 you'll spend.
Step 5: Total It Up and Add Headroom
Add every line's kWh/day. Then add 20% headroom — because families grow, guests visit, and nobody's estimates are perfect.
Worked example: 2,000 sq ft all-electric home
| Load | Daily kWh |
|---|---|
| Central AC (3.5 kW × 8 hrs) | 28.0 |
| Electric water heater (4.5 kW × 3 hrs) | 13.5 |
| Electric dryer (4 kW × 1 hr) | 4.0 |
| Range/oven (3 kW × 1 hr) | 3.0 |
| Well pump | 1.4 |
| Refrigerator + freezer | 2.4 |
| Dishwasher, washer | 2.0 |
| Lights, electronics, office | 3.5 |
| Phantom/always-on loads | 1.5 |
| Subtotal | 59.3 |
| + 20% headroom | ≈ 71 kWh/day |
Seventy-one kWh/day is a big number — and it's honest. Most all-electric 2,000 sq ft homes land between 50 and 80 kWh/day. If your home heats water and space with gas or propane instead, you might land at 25–35 kWh/day, which changes the entire equipment plan (and the budget).
This is why the audit comes first. The difference between a 30 kWh/day home and a 70 kWh/day home is roughly a $15,000 difference in system cost.
5 Mistakes That Wreck Load Audits
- Using the electric bill average. Your bill shows monthly kWh, which is useful as a sanity check — but it hides when you use power and your peak draw. You need both.
- Forgetting surge watts. The system runs fine until the well pump starts. Then everything goes dark.
- Sizing for spring and hoping for August. Size for your heaviest month, not your average one.
- Ignoring future loads. Planning an EV, a hot tub, or a workshop? Add them now. Retrofitting a bigger system later costs far more.
- Counting on behavior change you won't sustain. "We'll just not run the dryer" works for a month. Size for real life.
What To Do With Your Number
Your daily kWh number is the key that unlocks the rest of the series:
- Next: What Size Solar System Do I Need for a 2000 Sq Ft House? — Part 2, where your kWh number becomes a panel count.
- Then: Off-Grid Battery Bank Sizing — Part 4, where it becomes a battery bank.
- And: What Size Inverter Do I Need? — Part 5, where your surge numbers become an inverter size.
If your audit came out high, don't panic — the fastest wins are usually reducing load before generating power. Swapping an electric water heater for a heat-pump model can cut that line item by two-thirds. Every kWh you eliminate is a kWh you don't have to generate and store.
Frequently Asked Questions
How accurate does a load audit need to be? Within 10–15% is plenty. The 20% headroom covers the rest. What kills projects isn't small errors — it's skipping the audit entirely or forgetting entire categories like surge watts.
Can I just use my electric bill instead? As a cross-check, yes. Divide a heavy month's kWh by 30 for a rough daily number. But the bill can't tell you peak draw or surge, and those determine your inverter — so do the room-by-room audit anyway.
My house uses gas for heat and hot water. Does that change things? Dramatically. Gas heat and hot water can cut an all-electric home's load nearly in half. A 2,000 sq ft home on gas might audit at 25–35 kWh/day, needing a far smaller (and cheaper) system.
What about an EV charger? A Level 2 EV charger draws 7–11 kW — more than most homes' entire baseline. If you're planning an EV, add 10–15 kWh/day per 40 miles of daily driving to your audit, and consider charging it directly from daytime solar.
Do I need an electrician for any of this? The audit itself is DIY-friendly — it's just listing and arithmetic. But anything involving your breaker panel, new circuits, or grid interconnection should involve a licensed electrician. We'll cover the safety boundaries in Part 7.
About Nova Bliss — Nova Bliss is a US-based power systems company in Ocean Springs, Mississippi. We help homeowners and DIY builders cut their electric bills with wind, micro-hydro, and solar generation equipment. This post is Part 1 of our 11-part series on taking a 2,000 sq ft house fully off-grid. Questions? Call +1 228-696-3541.
About Nova Bliss — Nova Bliss is a US-based power systems company in Ocean Springs, Mississippi. We help homeowners and DIY builders cut their electric bills with wind, micro-hydro, and solar generation equipment. Questions? Call +1 228-696-3541.