TL;DR:
- August and September are the ideal window to service your heat pump, check your solar system’s performance, and review your energy tariff before peak winter demand.
- A heat pump that hasn’t been serviced in 12 months can lose 15–25% efficiency — exactly when you need it most.
- Switching to a smart tariff (Octopus Agile, Intelligent Octopus, or similar) before winter can cut your heating and charging costs significantly compared to a standard variable rate.
Most people think about their heating system when it stops working on a cold February morning. The smarter move is to spend a couple of hours in August — when the stakes are low and engineers aren’t booked solid — getting everything ready before it matters.
If you have a heat pump, battery storage, or solar panels (or any combination), here’s what’s worth doing now.
Heat Pump: Service It While You Can Get an Appointment
Heat pump engineers are dramatically harder to book in October and November than in August. Servicing a heat pump typically takes 60–90 minutes and costs £100–£200 depending on the engineer and your location. What gets checked:
- Refrigerant levels and pressure. Low refrigerant reduces efficiency significantly and, left unchecked, can damage the compressor — the most expensive component to replace.
- Defrost cycle function. The defrost cycle is what lets your air source heat pump function when outdoor temperatures drop below freezing. If it’s not triggering correctly, your system will struggle precisely when demand is highest.
- Outdoor unit fan and coil. Debris (leaves, dirt, plant growth) restricts airflow and reduces output. Clean the coil and surrounding area while the weather is mild.
- Flow temperature settings. Many heat pumps are installed and never reconfigured. If your system is set to run at a flow temperature above 45°C, it’s running less efficiently than it could. Ask your engineer to check whether a lower flow temperature is viable with your radiators or underfloor heating.
- Controls and thermostat calibration. Check that your smart thermostat or controller is set to a schedule that reflects how you actually live — not the default programme that came with the installation.
If you don’t have a service contract, book a one-off service now. MCS-certified installers, Vaillant ProPartner or Mitsubishi Diamond Dealer networks are good starting points for finding qualified engineers.
Solar Panels: Check Your Summer Data Before the Sun Goes Away
Summer is when your solar panels produce the most electricity. Before the seasonal curve turns, spend 20 minutes reviewing your monitoring data:
Compare this summer to last summer. A healthy solar system degrades very slowly — around 0.5% output per year. If you’re seeing 10–15% less generation than the same months last year, something is wrong: a faulty panel, a failing inverter, shading from tree growth, or soiling.
Look for unexplained gaps. If your monitoring shows periods of zero output during daylight hours, investigate before winter. An intermittently faulting inverter or microinverter failure that only shows up occasionally is much easier to diagnose and fix while generation is high.
Check inverter error logs. Most modern inverters (SolarEdge, SMA, Enphase, GivEnergy) have web portals or apps that log error codes. Review these even if the system seems to be working — minor faults often generate logged errors before they cause visible output drops.
Clean the panels if necessary. In most UK locations, rainfall keeps panels clean enough. But if you’re near a building site, agricultural land, or near a road with heavy traffic, a quick check is worthwhile. Soiling of 5–10% of the panel surface can reduce output by a similar percentage.
Battery Storage: Optimise for Winter Mode
If you have a home battery (Powerwall, Enphase IQ, GivEnergy, Pylontech, or similar), your summer and winter strategies should be different.
In summer: The battery fills from solar during the day and discharges overnight. Simple and largely self-managing.
In winter: There’s typically not enough solar generation to fill the battery during the day. Your strategy should shift to cheap-rate overnight charging — using an economy tariff to charge the battery from the grid when electricity is cheapest, then discharging during peak-rate periods.
Most battery systems support time-of-use (TOU) charging schedules. Set these now, before you need them:
- Programme the battery to charge overnight during off-peak hours (typically 00:30–04:30 on Octopus Go or Intelligent Octopus, or variable cheap windows on Agile)
- Set the battery to reserve a minimum state-of-charge (typically 20–30%) as a buffer for grid outages
- Review the battery’s temperature performance specs — lithium iron phosphate (LFP) batteries handle cold better than NMC chemistry. If your battery is in an unheated garage or outbuilding, consider whether it needs insulation or relocation.
Smart Tariff Review: Now is the Time to Switch
UK energy tariffs are least competitive in autumn and winter, when demand peaks. The window between now and October is when suppliers are most likely to offer attractive switching deals.
Octopus Intelligent is worth particular attention if you have an EV and a compatible home charger (Ohme, Wallbox Pulsar Plus, Zappi, or Andersen). The tariff provides very cheap overnight charging (typically around 7–8p/kWh) managed automatically by Octopus’s smart scheduling. With a heat pump and EV, this tariff can cut energy costs significantly compared to a standard variable rate.
Octopus Agile suits homes with battery storage and flexible demand. Prices vary by half-hour slot and are sometimes negative — meaning the grid pays you to use electricity. A well-programmed battery can automatically charge during negative-price windows and discharge during expensive peaks.
E.ON Next Drive and British Gas Electric Driver are alternatives if you prefer not to use Octopus. Compare using Uswitch or Look After My Bills, but pay attention to the unit rate during off-peak windows rather than just the headline rate.
If you’re on an economy 7 or economy 10 tariff with an older meter, check whether you’re eligible for a smart meter upgrade. Economy 7 rates are typically less competitive than modern smart EV or intelligent EV tariffs, and the off-peak window (usually 00:30–07:30) is less flexible than demand-side managed tariffs.
Draught-Proofing: The Cheapest Win Available
Before spending anything on energy systems, do a quick draught audit. In most UK homes, draughts from letterboxes, keyholes, gaps around windows, and loft hatches collectively represent more heat loss than a year of heat pump inefficiency.
- Letterbox brush draught excluders: £5–15
- Door draught excluders: £5–20
- Pipe and cable entry gap sealing (expanding foam): £5
- Loft hatch insulation (rigid foam board cut to fit): £20–40
These are weekend afternoon jobs with payback measured in weeks, not years. A heat pump running in a draught-prone house works significantly harder than one in a properly sealed one — and the efficiency gap widens as outdoor temperature drops.
Boiler Upgrade Scheme: August Deadline for Some Applicants
If you’ve been considering replacing a gas boiler with a heat pump and haven’t applied for the Boiler Upgrade Scheme (£7,500 grant for air source heat pumps, £7,500 for ground source), note that MCS-registered installers are typically much busier from October onwards. Applications require a valid EPC. If yours is out of date, commission a new assessment now — it typically costs £60–150 and takes a week to arrange.
Getting a quote now, with a planned installation in September or October, means avoiding the peak booking crush while still benefiting from a heat pump through its first full heating season.
A few hours of preparation in August can mean a winter of lower bills, fewer call-outs, and a heating system that actually performs when temperatures drop. The heat pump service in particular is the one action that makes the biggest practical difference — and the one most people leave until they’re already cold.