The 10-Minute Home Energy Audit
Published by C&T Smart Energy · March 2026
Most people assume they need a survey, a spreadsheet, or a smart meter to understand why their energy bills are high. In reality, you can spot the biggest issues in about 10 minutes — using nothing more than your eyes and your common sense.
This checklist is designed for typical South Wales homes (1930–1985 builds, gas boiler 10+ years old, EPC D–F), but it works for almost any property. If you want a professional view afterwards, our team can help with a proper whole-home assessment.
Step 1: Find your biggest bill driver
Look at your last bill (or your online account) and answer one question: is your cost mainly gas, mainly electricity, or both?
- Mainly gas: your heating system and heat loss are the priority.
- Mainly electricity: usage patterns, appliances, and solar/battery become more relevant.
- Both are high: you likely need a combined plan (insulation + controls + generation/storage).
Step 2: Check your boiler age and control setup
If your boiler is over 10 years old, it's often the fastest route to lower bills — but only if the rest of the system is set up correctly.
Quick check
- Do you have a programmable thermostat (not just an on/off dial)?
- Do you have TRVs on most radiators?
- Do you heat rooms you rarely use?
- Do you regularly run the heating “on” because the house feels slow to warm up?
If you answered “yes” to the last two, smart controls and zoning can often cut waste without changing the boiler.
Step 3: Do the “hand test” for heat loss
Walk around your home and place your hand near:
- external walls (especially north-facing)
- window frames and sills
- front/back doors
- loft hatch
- unused chimneys / open vents
If areas feel noticeably cold or draughty, your heating system is fighting a losing battle. That's why insulation and draught-proofing are often the best first spend — even before solar.
Step 4: Look for the “moisture clues”
Condensation isn't just annoying — it's a signal. It often means warm air is hitting cold surfaces.
Red flags
- water on bedroom windows in the morning
- musty smell in corners or wardrobes
- black mould spots around window reveals
- bathroom/kitchen steam that lingers for hours
The fix is rarely “turn the heating up”. It's usually a combination of ventilation, insulation, and correct heating control.
Step 5: Check your electricity “timing”
If you're considering solar or a battery, the key question is: when do you use electricity?Evening-heavy homes benefit most from battery storage.
- If most usage is 5–10pm: battery storage is usually worth exploring.
- If you're home in the day: solar-only can still perform well.
- If you have an EV: solar + battery + tariff planning becomes a serious advantage.
What to do next (simple decision)
- Cold + draughty? Start with insulation and ventilation checks.
- Boiler old + controls basic? Upgrade controls, then review heating system options.
- Electricity high + evening use? Explore solar + battery with realistic savings modelling.
Want a proper plan for your home?
If you'd like a clear, engineer-led recommendation (not a sales pitch), we'll assess your home and map out the best sequence of upgrades.