What an EPC G rating means, what it costs, and the routes up

Domestic energy performance certificates (EPCs) are rated from G to A and from 1 to 100. G is the lowest band, covering any property which scores 20 or below. There is nothing beneath it.

Lower letters indicate a more efficient building e.g an E is a better rating than a G. A more efficient building is also indicated with a higher number e.g. a 40 is more efficient than a 15.

Band G is rare: about 0.4% of certified homes in England and Wales, roughly 59,000 properties. They are almost never ordinary homes in poor condition; they are a specific combination of the most expensive heating fuels and fabric the calculation must assume is uninsulated.

Can I rent out a property with a G rating?

Not on a standard tenancy. The minimum energy efficiency standards (MEES) have required privately rented homes to rate E or better on all tenancies since April 2020, so a G-rated property, like an F-rated one, cannot be legally let unless a valid exemption is registered. Letting without one can attract fines of up to £5,000 under the current rules.

The exemptions regime exists largely for band G's typical cases: listed buildings where consent for wall insulation is refused, off-gas rural properties where the cost cap is reached before E is. Exemptions last five years and must be re-registered; our exemptions guide covers the categories. And the bar rises again in 2030, when new tenancies will need a C, with spending capped at £10,000 per property and fines of up to £30,000 under the new regime.

Why do homes end up in band G?

Electric panel heaters or bottled fuel on old, unevidenced fabric. In our precomputed RdSAP model of thirty typical homes, a pre-1930 bungalow with electric panel heaters and single glazing rates 5 G, with a modelled running cost of £2,301 a year. The same era detached house on panel heaters rates 9 G at £2,791 a year, and on LPG with single glazing it rates 16 G at £2,410.

There is a twist worth knowing: the rating is a running-cost index, but the certificate carries a second A to G chart for carbon, the environmental impact rating. The panel-heater homes above score far better on that chart (the detached example carries an EI of 65) because grid electricity now causes less CO2 per unit than gas. A G rating says a home is expensive to run under standard assumptions; it does not always mean it is the dirtiest.

How do I improve from a G rating?

Fabric first, then heating, and the order matters because every heating system multiplies what the fabric gives it. These worked routes come from the same RdSAP model, and each link opens the exact state on our interactive explorer:

Fabric alone clears the letting minimum: the 5 G bungalow above, keeping its panel heaters but with walls insulated, a 300 mm loft and LED lighting, rates 41 E and its modelled cost halves from £2,301 to £1,156 a year. Legal to let again without touching the heating.

Better electric heating on the improved fabric: swap the panels for high heat retention storage heaters and the same home rates 59 D at £810 a year; an air source heat pump instead reaches 57 D.

Solar carries it the rest of the way: the storage-heater version with a 5 kWp array rates 83 B at £341 a year. From the bottom of the scale to band B, on the same building.

Off-gas houses follow the same shape: the LPG detached example insulated the same way reaches 49 E still on LPG, and 64 D with a heat pump and 2.5 kWp of solar.

Check the paperwork first: where nothing is evidenced, the calculation assumes the age-based worst for every element at once, which is exactly the arithmetic that produces a G. Recorded evidence of cavity fill, loft top-ups or a newer heating system sometimes moves a home out of G before any work is bought.

*These examples are calculated for synthetic homes and may not be the right measures for your property. Proper consultation should be booked before committing to any improvements. The route button on our explorer finds the cheapest priced combination that clears C from any starting point.

Summary

An EPC G rating is the lowest band, held by about 0.4% of certified homes, and it sits two bands below the current legal minimum for renting. It is almost always produced by expensive heating fuel on fabric the calculation must assume is uninsulated, which is also why the routes out are so effective: insulation alone can lift a G to the letting minimum, and insulation plus modern electric heating and solar can reach band B on the same building.

Estimate a home like yours in three questions on our EPC calculator, or explore every measure on the EPC ratings explained guide, where every figure is a real RdSAP calculation.

The full band ladder: EPC rating C · EPC rating D · EPC rating E · EPC rating F · EPC rating G.