LPG and the Effects on Ratings.
Why is the SAP rating so low when entering LPG?
LPG (bulk and bottled) is much more expensive than mains gas, this has a dramatic effect on the SAP rating. The table below illustrates the impact of the fuel on the SAP and EI ratings for a three-bed semi with a condensing boiler. The fuel costs are those used for calculating ratings from SAP table 12, rather than those used to calculate the running costs on the EPC, which are located in the Product Database and updated every 6 months.
| Fuel | SAP rating | EI rating | Unit price p/kWh | Standing charge (£) | Emissions kg CO2 /kWh |
| Mains gas | 61 | 57 | 3.48 | 120 | 0.216 |
| LPG (bulk) | 36 | 53 | 7.60 | 70 | 0.241 |
| LPG (bottled) | 25 | 53 | 10.30 | 0.241 | |
| LPG (special condition 18) | 61 | 53 | 3.48 | 120 | 0.241 |
As you can see the unit cost of bottled or bulk LPG is more than double that of mains gas, even with the lower standing charge the impact on the rating is huge, using bottled LPG the rating has dropped by 36 points. The effect on the EI rating is less dramatic as the emissions factor (the amount of CO2 released for each kWh of energy) is only slightly higher for LPG.
LPG special condition 18 is currently specific to four towns; Colden, Llanfyllin, Llanwrtyd and Stornoway, where there is an independent LPG network and the LPG is charged at mains gas prices. To record this fuel you must have documentary evidence
If you discover that the property you are assessing has LPG as the primary fuel, it may be worth pre-warning the owner that the SAP rating may be low for the reasons given above.
There are photos of bulk and bottled LPG below. Note that you can find bulk LPG tanks underground, in which case the only visible part of the tank would be the green opening.